back to indexDr. Samer Hattar: Timing Light, Food, & Exercise for Better Sleep, Energy & Mood | Huberman Lab #43
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Welcome to the Huberman Lab Podcast,
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where we discuss science and science-based tools
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for everyday life.
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I'm Andrew Huberman, and I'm a professor of neurobiology
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and ophthalmology at Stanford School of Medicine.
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Today, I have the pleasure of introducing Dr. Samir Hattar
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as my guest on the Huberman Lab Podcast.
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Dr. Hattar is the chief of the section
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on light and circadian rhythms
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at the National Institute of Mental Health
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in Bethesda, Maryland.
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Dr. Hattar has many important discoveries to his name.
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He was one of a handful of groups
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that discovered the light-sensing neurons in the eye
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that set the circadian clock.
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This was a fundamental discovery made in the early 2000s
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that has led to an enormous number of additional discoveries
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on how light regulates our sleep, our immune system,
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our mood, mental health, metabolism, feeding,
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and many other important processes.
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If ever there was somebody who understands
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how all of these processes interact
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and can inform best practices for our daily behaviors,
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During our discussion today,
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Dr. Hattar answers questions that are absolutely essential
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for us to know about our health and wellbeing.
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For instance, how to align our sleep schedule
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with our activity schedule, such as exercise,
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and how to align light activity and exercise
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with our feeding rhythms.
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He presents a new model of how light activity
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and feeding rhythms converge to support optimal health,
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and when those are not aligned correctly,
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how our mental and physical health can suffer.
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It's a discussion that is rich with scientific mechanism,
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made clearly, of course, so everybody can understand,
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as well as specific protocols to deal with shifts
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in day length, shifts in activity,
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and in order to optimize sleep, metabolism,
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and wellbeing of various kinds.
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I learned so much from Samir, as I always do.
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He is an absolute wealth of knowledge
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on all things related to light and circadian rhythms,
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physiology, and neuroscience.
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I don't think you'll find anyone else
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as knowledgeable about these topics as Samir,
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and so I'm delighted that he joined us here on the podcast
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to share this information.
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Before we begin, I'd like to emphasize that this podcast
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is separate from my teaching and research roles at Stanford.
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It is, however, part of my desire and effort
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to bring zero cost to consumer information about science
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and science-related tools to the general public.
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In keeping with that theme,
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I'd like to thank the sponsors of today's podcast.
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Our first sponsor is Roca.
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Roca makes eyeglasses and sunglasses
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that are of the absolute highest quality.
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I've spent my career working on the science
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of the visual system, and I can tell you that one
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so they can really be worn in essentially any circumstances.
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that's R-O-K-A.com, and enter the code Huberman
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That's Roca.com, enter the code Huberman at checkout.
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Today's podcast is also brought to us by InsideTracker.
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for the simple reason that many of the factors
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that impact our immediate and long-term health
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can only be detected in a quality blood test.
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The problem with a lot of blood tests out there, however,
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So they made the whole thing very easy start to finish
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you can visit insidetracker.com slash Huberman
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to get 25% off any of InsideTracker's plans.
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Just use the code Huberman at checkout.
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Today's episode is also brought to us by Magic Spoon.
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Magic Spoon is a zero sugar grain-free keto friendly cereal.
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I am not ketogenic,
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meaning I don't follow a purely ketogenic diet.
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I tend to fast in the early part of the day.
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I tend to eat kind of low carb-ish
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through the middle of the day.
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And then in the evening I eat carbohydrates.
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That's what works best for me
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and allows me to feel alert all day long
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and to sleep really well at night.
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Magic Spoon is a terrific snack for me
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It's got some sweetness,
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but it doesn't take me out of that state
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where I'm sort of keto-ish, I would say.
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I'm not actually in ketosis,
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but I'm following more or less a low carb diet
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during the day, which keeps me alert.
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So either fasting or low carb,
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and Magic Spoon is consistent with that.
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And then as I mentioned before in the evening,
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I do eat carbohydrates.
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And now my conversation with Dr. Samer Hatar.
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Samer, thanks for sitting down with me.
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Yeah, we go way back.
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So you are best known in scientific circles
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for your work on how light impacts mood,
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learning, feeding, hunger, sleep, and these sorts of topics.
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So just to kick the ball out onto the field, so to speak,
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how does light impact the way we feel?
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So when I get up in the morning,
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I have the opportunity to interact with light
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in certain ways or to avoid light in certain ways.
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I have the opportunity to interact with sunlight
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or with artificial light.
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Maybe you could just wade us into what the relationship is
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between light and these things
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like mood and hunger, et cetera.
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So I mean, you do appreciate the effect of light for vision.
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So when you wake up in a beautiful area, beautiful ocean,
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light is essential.
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The sunrise, the sunset, blue sky, beautiful mountains.
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So that's your conscious perception of light.
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But light has a completely different aspect
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that is independent of conscious vision
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or image-forming functions.
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And that's how it regulates
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many important functions in your body.
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I think the best that is well-studied and well-known
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is your circadian clock.
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And the word circadian comes from the word circa,
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which is approximate, and dn is day.
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So it's an approximate day.
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Why is it an approximate day?
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Because if I put you or any other human being
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who have a normal circadian clock in a constant conditions
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with no information about feeding time, about sleep time,
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about what time it is outside,
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you still have a daily rhythm,
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but it's not exactly 24 hours.
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So it will shift out of the solar day
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because it's not exactly 24 hours
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and hence the name circadian.
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So just to ask a quick question about that,
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when you say you have this about 24-hour rhythm,
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how does that rhythm show up in the tissues of our body?
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Great, so great question.
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So it shows up at every level that we know we studied.
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It shows up at the level of the cell,
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it shows up at the level of the tissue,
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and it shows up at your behavior.
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The most obvious for you is your sleep-wake cycle.
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You sleep and you're awake and sleep at the 24-hour rhythms.
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And if you measure the sleep-wake cycle
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of humans who are maintained in constant conditions,
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you will see that the period length of the sleep rhythm,
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on average, is more than 24 hours.
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In humans, it's 24.2 hours.
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So you'll be drifting.2 hours every day
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out of the solar day if you don't get the sunlight.
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So the sunlight adjusts that approximate day
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to an exact day, so now your behavior is adjusted
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to the light-dark environment or the solar day.
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Okay, so if I understand correctly,
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if I were to go into a cave or I were to be
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in constant light and I didn't close my eyes
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in constant light, that I would still sleep
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in one coherent bout and I would still be awake
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for more or less one coherent bout, maybe a nap.
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But the total duration of my day, so to speak,
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would be a little bit longer than 24 hours.
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But if I'm in a condition like most people are,
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where the sun goes up and the sun goes down
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and I have some understanding of that sunrise and sunset.
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You don't have to have the understanding.
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You don't have to have conscious understanding.
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You have the detection.
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So circadian photoentrainment is the word we use
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in training the circadian clock to the photic environment.
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It's completely subconscious.
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You're not aware of it.
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It's not like vision or image forming
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where you actually know what you're looking at.
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So it's all hypothalamic.
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It's part of the brain that is not consciously driven.
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So you actually do not know when it happens
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or when it doesn't happen.
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And that's what we'll get into when I tell you
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why light affects your mood and why sometimes
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people don't know how to deal with light
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to improve their mood, for example.
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Okay, so this is a subconscious vision.
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Before you tell us about how light impacts mood,
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I'm curious, what is the relevance of adjusting
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this clock from a little bit longer
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than 24 hours to 24 hours?
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I mean, it seems like a small difference.
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24 hours and 40 minutes or 24 hours?
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Like, what's the relevance?
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I mean, why should we care about that short difference?
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So let's do the math.
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If you shift out 0.2 hours a day,
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in five days you're shifting out one hour.
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So you're literally one hour off
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in your social behavior in five days.
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In 10 days, you're two hours off.
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And if you're an organism that is living in the wild,
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shifting out of the right phase of the cycle,
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you could either miss food or you could become food.
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So it's really essential for survival.
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I think it's one of the strongest aspects of survival
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for animals to have the anticipation
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and the adjustment to the solar cycle.
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And for humans as well, when you say animals,
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I'm assuming that applies to us.
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So even though it's just a short bit longer than 24,
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if that accumulates over days,
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then you could find yourself very much out of phase
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with the rest of your species, essentially.
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So let's say it's 0.2 hours.
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So in five days, it's one hour.
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In 25 days, it could be five or six hours.
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You could be in New York and you're feeling
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as if you traveled from New York to London.
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So you will be having jet lag in New York,
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even though you didn't do a jet lag travel.
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So it's very important for the adjustment.
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And if we have time, maybe we could talk about
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why this is important for seasonality,
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because also it allows animals to anticipate
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the change in season.
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And the more you're high in the north or the south,
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the more that these weather changes occur very harshly
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and you have to be ready for them.
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And that happens in us as well.
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All right, we will definitely get into seasonality.
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Okay, so we've got this subconscious vision
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that aligns us with the turn of the earth.
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How does that work?
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What is the machinery that allows that to happen?
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And how does that machinery work?
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Yeah, so we knew that in mammals, including us,
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we are mammals, humans,
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that the eyes are required for this function.
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So if humans are born without eyes
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or the optic nerves are damaged,
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humans are not able to adjust to the solar cycle.
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So we know that the eyes are required.
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And since we thought we knew about the eyes a lot
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before 2000, we thought that-
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What did you say, before the year 2000?
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Before the year 2000, yes.
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We thought it's these photoreceptors in your retina
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that allow you to see.
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So in the human retinas,
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there are two types of photoreceptors.
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They are called rods and cones because of their shapes.
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And these rods and cones simply take the photon energy,
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which light is made of,
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and they change it in a way to an electrical signal
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that allow us to build the image of the environment
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Consciously, in this situation, because it's vision, right?
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It's image-forming vision, it's a visual cortex
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and associative cortices,
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which allow you to build conscious perception
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of the environment.
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However, people have found,
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including me with the work of David Berson
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and Ignacio Provencio,
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that there is a subset of ganglion cells.
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The ganglion cells are the cells that leave the retina,
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their axon, leave the retina, and project to the brain.
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So these words are stored to only relay
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rod and cone information from the light environment
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We found that a small subset of these ganglion cells
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are themselves photoreceptors that were completely missed
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And these are the photoreceptors
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that relay light environment subconsciously
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to the areas in the brain that have and house
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the circadian clock or the circadian pacemaker,
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which adjusts all the clocks in our bodies
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to the central brain clock that allows them to entrain
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to the 24 hour light dark cycle.
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So in the year, as I recall,
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because I was a graduate student at the time,
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in the year 2000, there was this landmark discovery
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made by you, Ignacio Provencio, David Berson, and others,
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that these cells exist that can communicate
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day and night information to the brain
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in this very small subset of cells.
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Since then, I've heard, but maybe you can confirm or refute,
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that this system that connects the eyes
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to the rest of the brain
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is actually the most ancient form of vision,
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that this is probably the form of vision
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that some early version of human beings had
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before they had pattern vision,
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before they could see colors and shapes and motion
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And that the same cells that perform this role
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are actually similar to insect eyes.
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I think I heard David Berson say once
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that we actually have a little bit of the fly eye
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What's he talking about?
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Yeah, so it's really interesting, actually,
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because these same IPRGCs we discovered,
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they contribute a little bit to image formation
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and now work from Tiffany Schmidt,
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specifically have proven that they do contribute
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to image forming functions.
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But they contribute to very limited aspect
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of image formation.
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So it fits your hypothesis
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that these are an ancient photoreceptors.
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The other thing that adds to that hypothesis
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is that they are expressed in cells
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that don't have any modification
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that make them look like photoreceptors.
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So the photoreceptors that I told you about
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that are important for vision, image formation,
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they have very specialized structures
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that allow them to pack these structures
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with photopigments.
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These are the photo detecting proteins.
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So they could detect a high sensitivity of photons
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that pass through them.
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These new photoreceptors don't have
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these specialized structures.
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So they just really need a lot of light at the time.
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We thought they need a lot of light to be activated.
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So that's why we think they are ancient
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and that's why I think they adjust to ancient functions
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that are as important as regulating your body,
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circadian clock to the solar environment,
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to solar day or to the light cycle.
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So you mentioned IPRGCs, intrinsically photosensors.
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So these are cells that connect the eye of the brain
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that behave like photoreceptors, essentially.
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And then you mentioned melanopsin,
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which is the actual pigment that converts the light
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into the electrical signal, more or less.
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And my understanding is that melanopsin
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was identified first in frog melanophores.
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So does that mean that we have like little pieces
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of frog skin in our eyes?
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So honestly, David Berson say you have a fly in your eye
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because it sounds better.
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The more accurate I think is that you have a frog skin
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in your eye, it's not as catchy.
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But really melanopsin, really the name melanopsin
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is from melanocyte opsin.
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So it's melanopsin because it was found
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in the frog melanocytes.
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You know the frogs can change their color depending on light
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and melanopsin drives this response.
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So when Ignacio Provencio first discovered
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these opsins in frogs, luckily he was smart enough
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to see if they are expressed in the frog eye.
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They were expressed in the frog eye
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and it what appears to be retinal ganglion cells,
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which I told you the one that connect the eye to the brain.
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He had the insight to go and see if they are expressed
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in the monkey eye and he found that they are also expressed
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in what appears to be retinal ganglion cells.
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And really that what opened the field wide open.
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Then David Berson did the seminal experiment
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where he went to the brain where the central oscillator,
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the oscillator that drives circadian rhythm in the brain
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called the suprachiasmatic nucleus
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that has been known for many years to receive retinal input.
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And he labeled the cells that project there
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and then he found that even if you destroy rods and cones,
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you could get light responses from these cells.
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So you could imagine he nearly fainted
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when he saw that these cells can respond independent,
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completely in the absence of rod and cone input.
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Yeah, I'll never forget reading those papers in 2000, 2001.
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I was at the meeting in DC when Ignacio,
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we call him Iggy, showed this image of this,
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basically what is frog melanophores in the human eye.
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And everyone was like, oh my goodness, this is the thing.
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And I want to get into how light actually
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can control circadian rhythms at the moment.
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But I think it's worth mentioning now
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that people who are pattern vision blind,
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so people who cannot see and no conscious vision,
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but have eyes, many of them still have these cells,
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these melanopsin intrinsically photosensitive cells
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and can essentially match or entrain, as we say,
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onto the light dark cycle.
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In fact, they possibly have no problems
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in circadian photo entrainment.
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They'll have enormous sleep-wake cycle.
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But they're totally blind.
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But they are totally image blind.
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And what's really interesting is that,
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and this story I heard from Chuck Sizler,
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so I'll give him credit,
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that some of these people who are image blind,
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usually they get dry eyes and they give them a lot of pain.
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And doctors used to think, oh, since they are image blind
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and they're getting dry eye,
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why don't you just remove their eyes?
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They're not using them anymore.
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And the minute they would remove their eyes,
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they start having cyclical sleep problems,
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indicating that now they are not entraining
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to the light dark cycle and are having cyclical jet lags
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when their clock shifts through the light dark cycle.
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That's really interesting.
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And I hear from a number of blind people,
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in my various aspects of my job,
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and a lot of them have issues with sleep, I think,
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in part because they don't realize
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that they too need to see light
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at particular times of day or night
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in order to match their schedule.
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Well, I think that's a perfect segue for us
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to talk about how light and viewing light
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can impact our sleep-wake rhythms.
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And then we will move into some of the other ways
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in which light can impact other forms of bodily function.
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Yeah, so I love the way you set it up
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because one of the most interesting and difficult aspect
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of trying to educate people about light effect
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on subconscious vision is that it's subconscious.
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So we're all aware of what we think is intensity
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because we see the room.
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But if you talk to people who know how to take photographs
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and stuff like that,
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they know that the intensity varies greatly.
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But our system, because we have to see the same way
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in very bright conditions and very dim conditions,
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we're not very good at estimating intensity consciously.
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So when you try to tell people about intensity,
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you really struggle because they think they know intensities
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but they really don't.
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You mean light intensity.
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So that the cones themselves have an incredible ability
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to adapt to different light conditions.
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So you can see at all different conditions,
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otherwise it'd be a disaster.
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You know, if you don't change the setting on your camera
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and you go from inside the room to the outside,
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it becomes completely white, you don't see anything.
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So if your cones don't adapt to the environment,
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then you're not gonna be able to see in this room
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and on the beach, right?
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But the problem is your IPRGCs,
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the cells that we talked about,
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they measure intensity pretty well.
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They really know what intensity is.
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They have a very good linear measurement of intensity.
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They don't adapt as well,
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they don't adapt actually that much, to be honest.
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So that tells you that subconsciously the system is used
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to measuring light intensity in a natural environment.
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Because when you're in a natural environment,
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you don't have industrialized lighting,
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then your system is functioning very well.
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But now when we change these environments,
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we could really mess up ourselves.
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So you have to teach people how to understand intensity.
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And that's something that you have to explain to people.
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And I think I love to do it myself.
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I do it in what is called the lowest amount of light
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required to allow you to see comfortably.
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So you have to do this as a fun experiment.
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Okay, so explain to me how this goes.
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And maybe we could break it up in the day
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into three or four parts.
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So let's say, assuming that most people wake up
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in the morning, as opposed to night shift workers, et cetera,
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we could talk about later.
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But they wake up in the morning,
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so let's divide the day into quarters.
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What is the proper way to interact with light
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in the first part of the day?
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So I honestly think the easiest thing is waking up.
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Get as much light as you can.
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Yeah, it's really nice.
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Your system is primed.
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If you're entrained, it's primed to get light.
link |
The sun should be out.
link |
Most animals in the wild,
link |
they actually seem to track the sun.
link |
The sun has a huge influence on life on earth.
link |
It's actually, life on earth is because of sun.
link |
In the morning, when you wake up, you need light.
link |
Okay, so what is the behavioral practice
link |
that you recommend?
link |
Does it, let's say somebody is in a condition
link |
where there's a lot of cloud cover.
link |
Is it important to get outside?
link |
So I have to tell you, the cloudiest day
link |
is gonna be much more brighter than your room.
link |
You could ask any photographer.
link |
A cloudy day, unless it's really dark, dark clouds,
link |
usually cloudy days have much more bright outside
link |
than inside the room,
link |
even when you have good lighting inside the room.
link |
So I think in the outside is usually,
link |
even when it's cloudy,
link |
you're gonna get enough intensity
link |
to help you adjust your cycle to the day-night cycle.
link |
So how long do you, these are general rules of thumb,
link |
but how long do you recommend people go outside?
link |
So if you do it daily, you possibly need very,
link |
if you do it daily, because remember,
link |
this thing is gonna happen on a daily matter.
link |
So it's like 15 minutes.
link |
So the clock is tracking it on a regular day.
link |
Absolutely, it's photon counting, it's tracking,
link |
I would say 15 minutes.
link |
If you don't do it daily, you may wanna increase it.
link |
And we'll talk about when you travel what you could do.
link |
But yeah, 15 minutes should be fun.
link |
You do it more, it doesn't hurt.
link |
And through a window, I was,
link |
my understanding is that through a window,
link |
it dramatically decreases
link |
the amount of light energy coming in.
link |
It depends of how, you know,
link |
how thick the windows are and how dark they are.
link |
So it, but it's also nice to go outside
link |
and to feel the season.
link |
I don't use sunglasses.
link |
Yeah, but you have the, your Jordanian photo pigment,
link |
you know, so yeah.
link |
Whereas my eyes are very sensitive, right?
link |
No, so I, but I personally,
link |
you know, if I'm in the shade
link |
or if it's not incredibly bright,
link |
I try to, especially in the morning,
link |
but I'm also an early person.
link |
So we have to differentiate between early.
link |
What time do you wake up?
link |
I wake up at 4.30 in the morning.
link |
But the sun isn't out yet.
link |
It's not out yet, so it's.
link |
So what do you do?
link |
You turn on artificial lights?
link |
I usually don't turn on artificial light
link |
because I know the sun is gonna come up eventually.
link |
But that's why I don't like the change
link |
in the timing that they do.
link |
Wait, well, what do you do between 4.30 a.m. and 7 a.m.?
link |
I mean, I look at my computer.
link |
So possibly I get enough light.
link |
But in reality, I mean,
link |
as long as you let your body get the morning sunlight,
link |
which I think is really, to me,
link |
and there is no evidence, but to me,
link |
this is, if you look at all animals, plants,
link |
this morning sunlight seems to be very important.
link |
And I, you know, we don't have experiments to show it,
link |
but I have a gut feeling
link |
that it has a huge impact on humans.
link |
Well, Jamie Zeitzer's lab at the Stanford Sleep Lab
link |
has shown that these early morning light flashes
link |
can adjust the total amount of sleep
link |
that one will get, makes it easier to get into sleep.
link |
And Ken Wright also did this beautiful camping experiments
link |
Right, maybe you should describe those
link |
because those are beautiful experiments.
link |
They are beautiful experiments.
link |
He took these, you know, college students
link |
that had the late onset of sleep and late waking time.
link |
And then he said, let's go camping
link |
and just don't use any artificial light
link |
and you could go to sleep as late or as early as you want
link |
and wake up as late as early.
link |
And he found a huge shift in their sleep pattern
link |
just by exposing them to the light-dark cycle.
link |
Even after they came back.
link |
I think it was two days of camping,
link |
reset the circadian clock.
link |
Seven days, but it lasted.
link |
Yeah, it's pretty amazing.
link |
Yeah, it's really incredible.
link |
Okay, so get bright light of some sort
link |
early in the day, ideally sunlight.
link |
Even on a cloudy day,
link |
it's going to be brighter than indoor light.
link |
And the other thing that I would like to mention to people.
link |
If you think it's very dim outside,
link |
let's say it's very cloudy, stay longer.
link |
So remember, intensity is only one component.
link |
Duration is also important
link |
because remember that the circadian system
link |
is not like the image system.
link |
In the image system, you have to change every second
link |
because you're looking at different objects.
link |
You have to change your perception.
link |
But for the circadian system,
link |
it's trying to figure out where am I
link |
in the day-night cycle.
link |
So the more you give them the information,
link |
the better you are.
link |
So if it's very bright, you don't need a lot
link |
because it's clearly going to make you fire like crazy.
link |
But if it's not bright, stay longer.
link |
Stay for one hour.
link |
Have your coffee outside or something like that.
link |
It's just going to help.
link |
I think you said something extremely important,
link |
which is that this circadian system
link |
is trying to figure out when you are in time.
link |
Not where you are in space.
link |
I said where you are in time, I meant when you are.
link |
Oh no, no, I wasn't correcting you.
link |
I just meant that, I think fundamentally,
link |
that's the incredible thing about this system,
link |
that you have this clock, this 24-hour clock in your brain,
link |
but it needs to be synchronized to the outside.
link |
So could we go a little deeper
link |
into this circadian setting behavior
link |
and come up with some general rules of thumb?
link |
So let's say it's a very bright day, extremely bright.
link |
No clouds, sun's out.
link |
You said 10 minutes, 15 minutes.
link |
And I'll tell you, if you're sensitive,
link |
you don't even have to go in the sun.
link |
You could be in the shade.
link |
There's going to be so many photons out there in the shade.
link |
It's going to be perfect.
link |
You don't even have to see the sun.
link |
You don't have to have the sun.
link |
It's great for vitamin D.
link |
That's a different story.
link |
You could do this for your skin and protect your skin.
link |
That's not my area of expertise.
link |
But for that effect on the circadian system,
link |
as long as you're outside in the shade and it's a sunny day,
link |
10 to 15 minutes should be ample amount.
link |
Okay, and then let's say it's kind of overcast.
link |
You know, it's not particularly bright
link |
or there's, you know, solid cloud cover,
link |
but, you know, obviously the sun is out,
link |
but it's not as bright.
link |
How long do you think it would take to set the clock?
link |
10 to 15 should be sufficient.
link |
Stay for half an hour, stay for 45 minutes.
link |
If it's very dark cloud, yeah, stay for longer.
link |
Okay, and if for some reason one finds themselves
link |
very far north and it's very, very dense cloud cover,
link |
how long and at what point should somebody consider
link |
using an artificial light source to mimic the sunlight?
link |
Yeah, honestly, this is where we don't have
link |
a lot of information still,
link |
because this is where we're going to discuss this
link |
maybe in more detail that if you put humans
link |
in artificial conditions,
link |
the circadian system is very sensitive to light.
link |
But in reality, in the real environment,
link |
light also is affecting other aspects
link |
that are independent of the setting
link |
of the circadian basemaker.
link |
And these which we call the direct effect of light
link |
on mood, for example.
link |
So that is very hard to figure out
link |
what intensity you need to use,
link |
and we haven't done enough experiments,
link |
because the system has been discovered just recently.
link |
But I would say if you use bright light in the morning,
link |
and I mean, it's hard for me to give numbers,
link |
it can get complicated.
link |
But yeah, I mean, if you're,
link |
honestly if you're that far north
link |
and you're in the winter and you want to get,
link |
make sure you don't use these light boxes,
link |
I would suggest that personally, but that's it.
link |
I use, it's actually not designed for circadian setting,
link |
but I have a 930 lux light pad that I bought,
link |
and I bought it, they're very affordable
link |
compared to the Dawn simulating lights,
link |
which are quite expensive, frankly.
link |
And I put it there, and so I just basically,
link |
when I wake up in the morning,
link |
I use that until the sun comes out,
link |
and then I make sure once the sun is out, I go outside.
link |
But I keep that thing on all day.
link |
And I don't know if that's good or bad.
link |
Is it good or bad?
link |
I honestly, I don't think being exposed to bright light
link |
in the day is going to ever be bad,
link |
because really, if you're outside in the day,
link |
unless, you know, the worst is gonna happen
link |
if the temperature is very high,
link |
your body's gonna say don't dehydrate and go to sleep.
link |
So you could tell actually sometimes when it's very hot,
link |
the more you get exposed to bright light,
link |
the sleepier you feel in the afternoon,
link |
which is counterintuitive.
link |
And that's to protect us, you think, against dehydration?
link |
I think if you think about the human evolution
link |
from near the equator in the,
link |
between noon and a certain time in the afternoon,
link |
it would have been very hard for you to maintain
link |
physiological homeostatic function,
link |
being active at this very high temperature time.
link |
So I think napping was a way,
link |
that's why I think it has a major function,
link |
which is still, napping was a way to somehow
link |
take you away from that dangerous zone.
link |
And maybe that's why people in the north,
link |
they say in the winter, we can't wake up in the morning
link |
because they don't have this long light,
link |
so they sleep it more at night.
link |
But in the summer, they say we feel like we can't go to sleep
link |
we have to put all these dark curtains.
link |
So I think, you know, venturing that much north,
link |
up north, has been, came up with problem
link |
because evolution was used to a certain light environment
link |
that was completely changed with a human,
link |
with other animals, I think, that lived there longer.
link |
They have come up with very interesting adaptation
link |
of actually measuring even very small changes
link |
in the light, in the light intensities that still occur.
link |
So even if you're near the poles,
link |
even though it's always light,
link |
but there is a change in the light intensity
link |
across the day and night cycle.
link |
So your system, if it's linear,
link |
and remember I told you that IP RGCs are incredibly linear,
link |
can still measure, oh, this is lower light than higher light
link |
if the organism has the ability to do that.
link |
I see, you know, it's interesting,
link |
I've spent so much time learning from you,
link |
fortunately, about these cells,
link |
and yet I never really appreciated until now how,
link |
on the one hand, they are tracking the amount of light
link |
to understand when we are in time
link |
relative to the 24-hour cycle,
link |
but also that you keep mentioning
link |
this linear measurement of intensity,
link |
that they really are trying to figure out
link |
when we are in time by measuring the intensity of light.
link |
And of course, the sun is the most intense source
link |
of light available to us.
link |
So, okay, so I think we've nailed down
link |
that first part of the day.
link |
Basically, it's get 10 to 30 minutes,
link |
depending on how bright it is,
link |
and try and do that as often as possible
link |
to give the system a regular-
link |
Daily is the best.
link |
This system is really about,
link |
and you'll see that even for the effect on depression,
link |
it's about multiple days.
link |
So you don't have to worry if you missed it one day,
link |
you know, stay longer if you want,
link |
but if you're in a hurry and you want to do other stuff,
link |
that's a great recommendation.
link |
So you might want to compensate with some extra time
link |
if you missed a day or two.
link |
And this is why I've heard you say before,
link |
it's entirely possible to get severely jet-lagged
link |
without traveling.
link |
Simply by staying in, being on your phone too much,
link |
not getting the sunlight.
link |
And you saw this during the pandemic.
link |
A lot of people mentioned
link |
that their sleep-wake cycles suffered a lot.
link |
Because if you're not going out,
link |
and if you're staying at home,
link |
and you don't have big windows,
link |
and you're waking late, waking up late,
link |
and then you're using very bright light till late at night,
link |
your body's going to shift.
link |
And now your day is going to start instead of,
link |
like really when the sun comes up,
link |
let's say at six o'clock in the morning,
link |
your day is going to start at 11 o'clock in the morning.
link |
That's what your body's going to think
link |
is the beginning of the day.
link |
So then you're not going to be able to sleep
link |
at 10 o'clock at night,
link |
because now that's really for your body
link |
is completely different timing.
link |
And you could see this happen during the pandemic
link |
at a very high scale.
link |
People get delayed in their sleep-wake cycle a lot.
link |
And there is this idea of chronotypes
link |
that we all each intrinsically have a best rhythm
link |
of either being a morning person,
link |
you called yourself an early person,
link |
or more of a kind of standard,
link |
to bed around 10, 30, up around seven type thing.
link |
And I think there are now good data,
link |
correct me if I'm wrong,
link |
from the National Institutes of Mental Health and elsewhere,
link |
showing that the more we deviate from that intrinsic rhythm,
link |
the more mental health issues
link |
and physical health issues start to crop up.
link |
So there is great data on this,
link |
and there is a couple of things that complicate this.
link |
The first is the people who usually are late,
link |
they tell you that the society doesn't accommodate.
link |
What, by late, what do you mean?
link |
People that wake up late and go to sleep late?
link |
Go to sleep late and wake up late.
link |
They have an overwhelmingly higher level of depression
link |
I mean, clearly, I mean,
link |
the reason that people say sleep early, wake up early,
link |
because human notice that people who wake up,
link |
go to sleep early and wake up early,
link |
they do better in life.
link |
They just perform better.
link |
But the question is, is that intrinsic to the system,
link |
or is that society?
link |
Because society start things usually early or late.
link |
That's a hard question to ask.
link |
We discriminate against late risers.
link |
In a way, we discriminate, right?
link |
But the other explanation is Ken Wright's experiment.
link |
if they were truly chronotypically late,
link |
why would they shift so easily when you put them in the,
link |
if you were really chronotypically late,
link |
and there is a phase relation
link |
between the light-dark environment
link |
and your circadian clock,
link |
then doing this camping experiment
link |
should not have caused much changes,
link |
because it's not that light is gonna affect you
link |
It's that this is the relationship that your body decided,
link |
that I'm a late sleeper, late waking.
link |
So, honestly, I'm still unable to figure out
link |
how much of this late waking up
link |
is controlled by the light environment,
link |
and how much is intrinsic.
link |
I'm sure there are differences.
link |
But are they as big as we see in the environment?
link |
Because you have people that go up to sleep at 7 p.m.
link |
and wake up at 1 a.m.
link |
These are clearly advanced phase.
link |
So people that go to sleep at 7 p.m.
link |
and wake up at 1 a.m.
link |
and feel good doing that.
link |
I'm not so sure they feel good,
link |
but a lot of the time you talk to people,
link |
they say they are high achievers,
link |
but they suffer because they go to 7 p.m.,
link |
wake up advanced phase sleep syndrome,
link |
they call it, they call it a syndrome.
link |
But then you have people who would not be able
link |
to sleep till 5 a.m.
link |
and not be able to wake up till 3 p.m., right?
link |
And I'm not so sure that the circadian system
link |
is that variable in the human population.
link |
I mean, clearly there are maybe some genetic factors
link |
that make a small percentage of everything
link |
with a bell shape.
link |
But I think most of the time,
link |
the light environment may play a role.
link |
And once, as we've talked about,
link |
this is a long-term effect of light.
link |
Once you get into a rhythm,
link |
and I don't mean it as a pun in reality,
link |
once you get into a rhythm,
link |
it's hard to break out of that rhythm.
link |
Because if you start sleeping late and waking up late,
link |
you're not getting the morning sunlight.
link |
And so you're just gonna be late.
link |
And if you're like me, waking up early,
link |
you're getting the morning sunlight.
link |
You're getting what Zeisler said, I said his last name wrong,
link |
the one in Stanford who did the-
link |
Oh, Jamie Zeisler.
link |
He actually worked for Zeisler, so Zeisler and Zeisler.
link |
Yeah, there are a lot of Zs and Is in their names.
link |
Both phenomenal scientists.
link |
Well, what it seems to me is the case
link |
is that the only way to really know
link |
if you're meant to be an early bird, as they call it,
link |
an early person or a late person,
link |
or somewhere in between, is to get morning sunlight
link |
and figure out whether or not that makes you feel better.
link |
And to understand, to be educated
link |
about how to measure intensity,
link |
how to measure, I put it between quotation,
link |
because you either get a measuring device,
link |
but you cannot depend on your eye to measure intensity.
link |
Okay, so how do we do that?
link |
Because you keep coming back to this,
link |
so that tells me that it's important.
link |
It's very important.
link |
So there are apps, like free apps, like Light Meter,
link |
where you can walk around and hold the button down
link |
and see how many lux are in the environment.
link |
These are complicated because you have to point them
link |
to specific regions.
link |
So how do people start to develop an intuitive sense
link |
of the measurement of intensity?
link |
Yeah, I think at one point I posted on Instagram
link |
how I keep my nighttime at home.
link |
And I found out that my night vision is very strong.
link |
So I found out that I, especially in the winter,
link |
I only need candle light.
link |
So I literally use these tea lights,
link |
and I put like 15 or 20 of them.
link |
I could see it clearly doesn't affect my circadian system.
link |
You and your cats.
link |
And your wife, of course.
link |
It's just great, it's just great, right?
link |
But I don't expect people
link |
to have the same night vision as me.
link |
So the simple, I mean, I tell people, do the experiment.
link |
So if you put three or four lights in your room,
link |
switch to, sit for 15 minutes, switch two off.
link |
Let's say you're using five.
link |
And see, after 15 minutes,
link |
you will not recognize you switched these two off.
link |
My gut feeling is that most people would need
link |
at least 10 times less light than they use at night to see.
link |
The problem people use it,
link |
because most of the time they didn't see
link |
the morning sunlight.
link |
They are actually hungry for light without their knowledge.
link |
So they come switch all these lights on,
link |
but at the wrong time, because they woke up late.
link |
Okay, now I understand.
link |
So this morning light viewing goes way beyond
link |
setting your clock.
link |
It's also a way to determine
link |
how little light you need later in the day.
link |
And we're going to talk about this in a moment,
link |
but how little light you get later in the day
link |
is a very strong determinant of things
link |
like when you will wake up,
link |
whether or not you wake up feeling refreshed, et cetera.
link |
I'm going to break it on your show, Andrew,
link |
that I'm going to tell you,
link |
I think there is something else
link |
that people need to think about,
link |
which is the tripartite model.
link |
That this model incorporate three components
link |
we should talk about in details
link |
that allows us humans and all animals
link |
to incorporate the circadian clock
link |
and its relation to light,
link |
the homeostatic drive,
link |
and the direct effect of the environment,
link |
which includes stress, light, all kinds of stuff.
link |
They have to be incorporated together.
link |
If you think, that's what I think right now,
link |
if you think of one alone,
link |
you will always miss something.
link |
And when you think of them as a whole,
link |
things really become clear.
link |
It's actually quite amazing.
link |
Okay, well, we will definitely want to hear
link |
about your tripartite theory
link |
and go into detail about this homeostatic mechanisms.
link |
I want to make sure that for people who are thinking now,
link |
I'm sure, about light and how it impacts them.
link |
So the morning light viewing behavior,
link |
I like to think we've tacked down clearly.
link |
And thank you for that
link |
because there's so much information out there
link |
and I've tried to relay that information.
link |
Of course, you're my primary source
link |
for all things circadian,
link |
as well as Jamie and others, of course, Matt Walker.
link |
But I think you've made that very, very clear.
link |
Now, let's say I've gotten my morning sunlight, okay?
link |
Made my bright artificial light.
link |
And throughout the day, you said to get a lot of light.
link |
So I'm working at my desk.
link |
Maybe I'll go out during the day a few times,
link |
but I'm working at my computer, I'm doing things.
link |
Is there anything about light viewing
link |
in the middle of the day that people should keep in mind?
link |
Or can they just sort of freestyle it,
link |
depending on what they're doing?
link |
Most people are not in a dark room throughout the day.
link |
My gut feeling, if you got your morning sunlight,
link |
you walk from your car slowly or you walk to work,
link |
you didn't wear sunglasses
link |
when the lights were still dim in the morning,
link |
that you could freestyle it.
link |
That even if you don't get a lot of light,
link |
there is a way to just, you know, in the day,
link |
you don't have to just worry
link |
about getting a lot of bright light.
link |
But personally, I like to do that.
link |
So I go out at lunch and have my lunch outside as well.
link |
This reminds the body that here it is even brighter now.
link |
But the evidence is that you could literally
link |
help your circadian clock by giving lights at dawn and dusk.
link |
But again, if you think of the tripartite model,
link |
this may be important versus circadian clock,
link |
but is it important for your mood?
link |
So that's where I think you need, or the homeostatic drive.
link |
So that's where you need to think about it.
link |
So for the clock, for entraining your clock,
link |
you literally can entrain it only by the dawn sunlight.
link |
You actually don't need dawn and dusk.
link |
You can even forget that.
link |
Yeah, and I appreciate that you're distinguishing
link |
between circadian effects and other effects of light.
link |
You're being very precise, which is appreciated.
link |
Until we hear about this tripartite model,
link |
which we will cover, for the sake of the discussion,
link |
let's treat the light viewing behavior
link |
as what are the benefits or drawbacks of viewing light
link |
for all biological purposes, not just circadian settings.
link |
So in the morning, it's clearly going to set the clock.
link |
And then during the day, if I understand correctly,
link |
the idea is to get as much bright light as you can
link |
because you're feeding, it sounds like,
link |
a sort of light hunger.
link |
I love this way to put it.
link |
I think there is a weird light hunger.
link |
Considering that we're not photosynthetic organisms,
link |
there is a weird light hunger in animals
link |
that they need to measure, they need measure.
link |
And I think that relates to the season
link |
because the whole reproduction cycle of animals
link |
is gonna depend on the availability of food
link |
in the environment.
link |
And if you don't know when the season's gonna happen,
link |
they don't have calendars,
link |
it's gonna be very hard to survive.
link |
So I think that's why we have this light hunger.
link |
That's a major hypothesis.
link |
It's not been tested.
link |
So then afternoon and evening start to approach.
link |
So I've had this weird experience.
link |
Maybe you can psychologically
link |
or biologically diagnose me now, Sameer.
link |
So where if I go into a movie in the afternoon,
link |
like a matinee, and I come out and it's dark,
link |
I notice a significant drop in my mood
link |
and my ability to go to sleep.
link |
Whereas if I get some view of the light in the evening,
link |
it doesn't have to be the sunset,
link |
although sunsets are nice,
link |
but I get some light pulse in the afternoon
link |
that I have no trouble whatsoever.
link |
And this happens in a daily, on a single time to watch?
link |
That's interesting.
link |
And then you mentioned the camping experiment
link |
where when they went camping,
link |
they're seeing the sunrise and the sunset.
link |
So what should people do in the afternoon slash evening time
link |
in terms of their light viewing behavior?
link |
I mean, the best thing to do
link |
is to let the natural light creep in into darkness, right?
link |
That would be the best.
link |
But clearly that would be inefficient.
link |
You wanna go home, you wanna read,
link |
you wanna talk to your kids,
link |
you wanna talk to your family.
link |
So I think, you know, it's nice to extend the day.
link |
I don't think that's wrong.
link |
If you somehow can block that light
link |
from affecting your circadian clock.
link |
So should people use blue blockers in the evening?
link |
I personally do not like any blockers
link |
that take a single wavelength of light.
link |
Because again, if you think of a holistic approach,
link |
yes, the blue blocker is gonna prevent you
link |
from affecting your circadian clock very much,
link |
but then your vision is gonna be distorted
link |
because we always see in full spectrum.
link |
The sun has this beautiful spectrum, right?
link |
And then when you start seeing without the blue,
link |
things look yellow and it can get really weird, right?
link |
I mean, so I personally,
link |
I've tried the blue blocker and I couldn't even wear them.
link |
I thought they were just really horrendous, to be honest.
link |
Well, along the lines of blue blockers,
link |
I think a lot of people mistakenly wear them all day long.
link |
Oh my God, that would be very bad.
link |
A lot of people do that.
link |
A lot of people do that.
link |
They think that the blue light is bad.
link |
I think that the concept of blue light being bad
link |
led to a lot of product development.
link |
And a lot of people are just assuming
link |
that viewing blue light is what was giving them headaches
link |
when, in fact, it might have just been looking
link |
at screens at close distance.
link |
So here's the problem, right?
link |
I mean, the blue light got the bad reputation
link |
because people who gave a pure blue light
link |
showed that it caused a huge retinal damage.
link |
But again, if you're using blue light in its pure form,
link |
it has a lot of energy because it's shorter wavelength.
link |
But we're talking about full spectrum light.
link |
There are ways now where you could change the spectrum
link |
of the light and keep it white between day and night
link |
and change the content of the color without you noticing.
link |
So you don't even have to affect your vision.
link |
So how would you go about doing that?
link |
So you just lower the level of the blue light.
link |
You don't have to eliminate it.
link |
So just dim the lights.
link |
Dim the blue, then increase the yellow,
link |
but keep all the colors in a certain white
link |
so you could have different warmness of white.
link |
And people know how to do this.
link |
Physicists know how to do this.
link |
People who work with light know how to do this.
link |
Well, maybe somebody in the wellness slash,
link |
I don't like the word,
link |
but biohacking or optical community will do this.
link |
I think it's really important.
link |
I see so many people wearing blue lockers.
link |
I don't know why they love blue.
link |
Well, I think they're just uninformed.
link |
And to be honest, it's easy, right?
link |
It's easier to explain to somebody,
link |
if IPRCCs respond mostly to blue,
link |
remove blue, you'll be fine, right?
link |
But that's not as simple as that
link |
because they also receive road and cone input.
link |
So you want to actually,
link |
and we could go into details
link |
that's boring for you listeners,
link |
but it also affect the adaptation properties
link |
of the whole retina.
link |
So you don't want to do something so drastic
link |
that you take just one color of the spectrum.
link |
It just seems very counterintuitive to me, to be honest.
link |
You've told me before as well
link |
that just because these intrinsically photosensitive
link |
circadian setting ganglion cells
link |
respond best to blue light,
link |
if the light is bright enough,
link |
because they also get input from other components of the eye,
link |
it doesn't matter if you block the blues.
link |
If you're looking at bright light at night,
link |
you're going to disrupt your circadian cycle.
link |
And that's why I didn't want to go into the boring details,
link |
but themselves, the photoreceptors
link |
have a wide range of responsiveness.
link |
So they are most sensitive to blue light,
link |
but that doesn't mean they don't respond to green light
link |
or to shorter than blue light.
link |
They respond to very, very wide spectrum
link |
with different sensitivities.
link |
So unless you understand the system, just removing 480,
link |
I don't think it's going to do anything.
link |
480 nanometers, yeah.
link |
So your home is a cave at night, basically.
link |
It's a nice cave with candles, right?
link |
And you and your cats and your lovely wife,
link |
who I know who's also a phenomenal scientist
link |
Thank you, yeah, she is.
link |
But you do keep your home quite dim to dark at night.
link |
In fact, I did go to meetings with some of my friends
link |
who work on this and they really struggled with me.
link |
They said we could have broken our legs
link |
living in the same light environment that you do.
link |
So I am an extreme, but I measured it for myself
link |
and I asked Reiji, my wife, if she's okay with it.
link |
She also liked the dimness.
link |
Both of us can see well in dim conditions
link |
and that helps us a lot.
link |
But I think you have to measure it for yourself.
link |
You really have to do, it's a very simple experiment.
link |
Just try to dim the light as much as you can.
link |
I call it the minimum amount of light
link |
you require to see comfortably.
link |
And that's how you want your environment ideally at night.
link |
This is what I think is the game changer.
link |
If you reach to a level where it's just barely,
link |
you're literally on the cusp of seeing uncomfortably
link |
versus seeing very comfortably,
link |
you are gonna be very much better
link |
than I don't like to make it completely dark.
link |
I think complete darkness induce anxiety in humans,
link |
to be honest, so I don't like complete darkness.
link |
Kids don't like complete darkness.
link |
They like night light.
link |
Even nocturnal animals don't like complete darkness.
link |
I mean, we have studies in animals that are nocturnal
link |
that if you put them in complete darkness
link |
for several weeks, they have severe anxiety
link |
and depression-like effect.
link |
So keep the light dim.
link |
You know, use red light that is very dim
link |
if you wanna keep the room for sleeping.
link |
Red light that is very dim has very small effect
link |
on circadian clock.
link |
And below 10 lux of red light
link |
literally doesn't affect sleep at all.
link |
So there are ways to do it.
link |
It's just we need to educate the public.
link |
And I feel like you literally need a whole lecture
link |
to just explain to the people how to deal with light
link |
because it's not as simple as people think.
link |
Well, that's what we're doing here.
link |
We're stepping through it piece by piece.
link |
And the reason we're doing that
link |
is because it's not as simple as saying
link |
just block blue light or get a lot of light during the day.
link |
I mean, just put it in perspective to tell it,
link |
we only have three different cones in our retina
link |
that respond to three different colors.
link |
We call them red cones for simplicity,
link |
green cones and blue cones.
link |
Yet we have only three of these,
link |
but we could see massive palette of colors.
link |
So that tells you something.
link |
If the system was just simply about a single color
link |
and it's just removing 480 or just blue is sufficient,
link |
then we should only see in red, yellow and blue.
link |
We shouldn't see all these different hues of color.
link |
But because the system is not that,
link |
we see all these different colors.
link |
And that's why it's important to remind people
link |
that the white light is made of many different colors.
link |
It's actually like the rainbow.
link |
That's why you see the rainbow.
link |
It's made of many colors.
link |
White light is never truly white.
link |
It's made of lot of different colors.
link |
It's like the Pink Floyd album cover.
link |
Exactly, exactly, exactly.
link |
So dim at night, maybe dim red light ideally,
link |
or candlelight, find that minimum required light level.
link |
Just make sure when you lower the light,
link |
sit for at least 10 to 15 minutes.
link |
Let your system adapt.
link |
Because if you had it bright light and you switch it off,
link |
surely you're gonna suffer
link |
because your system didn't adapt it.
link |
It was used to very bright light.
link |
So you want to engage your rods,
link |
which take a long time to dark adapt.
link |
So that's why I tell you, just wait a little bit.
link |
Don't just switch it off, I don't see, put it on.
link |
Put it off, sit down, wait for 10 minutes,
link |
ideally 15 minutes, and then see how you see.
link |
And then once you do that,
link |
you will notice that actually,
link |
yeah, I could see quite well, even with much less light.
link |
What do you do regarding screens?
link |
Yeah, that's the hardest thing.
link |
Again, I mean, there are beautiful programs
link |
that change the whole intensity and color of the screen.
link |
These could help dim your screen at night
link |
to the lowest part.
link |
I mean, yes, you won't see it
link |
when you wake up in the morning,
link |
but then you can increase the intensity.
link |
So try to decrease.
link |
I mean, just what we were talking about.
link |
Think of light intensity, duration, color, and time of day.
link |
You really have to keep these four things together, right?
link |
We've roomed together at a couple of meetings
link |
from time to time, no longer,
link |
because one of us, not to be named,
link |
has a severe snoring issue
link |
that made the other one pseudo homicidal.
link |
You can guess who that was.
link |
But I've seen you check your phone after dark once or twice,
link |
and you did it by pointing your phone away from you, right?
link |
And actually I'm sort of half joking,
link |
and you dim it quite a bit.
link |
I'm sort of half joking,
link |
but it actually makes sense
link |
that if you shine a flashlight in your eye,
link |
it's much brighter than if you shine a flashlight.
link |
So if you just look on the side,
link |
most of the light is going to go this way,
link |
and you're only seeing this way.
link |
Okay, and as silly as that might seem to people listening,
link |
I mean, what it means is that
link |
getting bright light in your eyes at night
link |
is something that you really want to avoid,
link |
but there is the reality then.
link |
And even when I check sometimes,
link |
if I have something and I check it so fast
link |
and switch it off so fast,
link |
so I'm also aware of the duration.
link |
I'm also aware of the duration, right?
link |
So duration, intensity, color, and time of day.
link |
Ideally, I should not check iPhones and iPads.
link |
I don't use iPad at night
link |
because it's hard to lower it enough,
link |
because it's huge.
link |
But even my iPhone, I try not to use it at night.
link |
And like, once it becomes 8.30 or 9,
link |
I don't look at it at all.
link |
Unless it's World Cup or Euro Cup,
link |
in which case, Sandra's on 24 hours, everybody.
link |
That's only every four years.
link |
He's a big soccer fan.
link |
All right, this has been incredibly, no pun, illuminating.
link |
Let's talk about the relationship between light
link |
and some of these other non-circadian
link |
or pseudo-circadian effects.
link |
And we will try and link those.
link |
But you had what I consider absolutely landmark,
link |
beautiful paper published in Nature a few years ago,
link |
showing that if you disrupt the exposure to light
link |
or the timing of the exposure to light,
link |
that there are dramatic effects on the stress system
link |
and on the learning and memory system.
link |
We could talk about each of those separately or together.
link |
What are the effects on stress and the effects on learning
link |
when light viewing behavior
link |
and sleep-wake cycles are disrupted?
link |
So just to remind you, you know that,
link |
but to remind your listeners
link |
that I was trained as a circadian biologist.
link |
So I really was indoctrinated into thinking
link |
that light has to affect the clock,
link |
which then cause all these different effects.
link |
So that's what I believe.
link |
That's what would have made me really happy.
link |
And then Tara LeGates and Cara Ultimas joined the lab
link |
and said, and we started discussing a lot of data
link |
and we said, what if there is a direct effect of light
link |
that we're missing independent of the circadian clock?
link |
So this is not an easy question to answer
link |
because as we've been talking all along,
link |
light affects the circadian clock.
link |
So how could you give light at different times of the day
link |
and not mess up the circadian clock?
link |
Luckily, we came up with such a way
link |
and that's why it was important to do this experiment
link |
the way we did them.
link |
And we proved that this light-dark cycle
link |
does not disrupt the clock.
link |
There is still a circadian rhythm
link |
and does not cause sleep deprivation.
link |
And yet, surprisingly,
link |
if you give light at the wrong time of the day,
link |
even without disrupting the circadian clock
link |
or without causing sleep deprivation,
link |
as you mentioned, you get huge mood changes
link |
in the organisms and you get learning deficit.
link |
So this really, and at the time,
link |
people have really hit us hard.
link |
I mean, it was really hard to publish this work
link |
and you could, yeah.
link |
Well, it came out in nature, so in the end you prevailed.
link |
But I want to make sure that I understand.
link |
So you're saying that, yes,
link |
there are effects of light on the circadian rhythm.
link |
Sleep, meaning sleep and wake fullness.
link |
However, there are direct effects of light on mood
link |
that can be dissociated
link |
from the effects on sleep and waking.
link |
So if I interpret that correctly,
link |
that could mean that when we view light
link |
and how much light could make us feel happier
link |
or less happy or even depressed,
link |
stress, learning, et cetera.
link |
Even if we're sleeping
link |
and waking up at the appropriate time.
link |
I mean, eventually,
link |
because we're talking about the whole system,
link |
eventually when you start having the other problems,
link |
you also develop sleep problems.
link |
But you're absolutely right.
link |
And in fact, now research from Diego Fernandez
link |
in the lab have found that now we know
link |
that they actually require different brain regions.
link |
So we don't only have a theory,
link |
we don't only have a light environment
link |
that showed they can be dissociated.
link |
We know that they use completely different brain regions.
link |
So the SCN that I told you about earlier,
link |
the place where the central pacemaker is,
link |
the one that receives direct input from the retina
link |
through the iPRGCs to adjust your circadian clock
link |
is not the area that receives the light input
link |
for mood regulation.
link |
It's a completely different brain region.
link |
What's the brain region called?
link |
So the brain region,
link |
we called it the perihabineular nucleus.
link |
I'm not so sure how good or bad the name,
link |
but doesn't matter, it's the PHB.
link |
And what's really amazing,
link |
this region also receives direct input from the iPRGCs,
link |
but projects to areas in the brain
link |
that are known to regulate mood,
link |
including the ventral medial prefrontal cortex,
link |
which has been studied for many years
link |
to be impacted in a human depression.
link |
So just by this amazing serendipity
link |
to find that a region that is so deep in the advanced brain,
link |
like the prefrontal cortex is your executive brain,
link |
one of the most elaborated in humans,
link |
to see that they receive input
link |
from these ancient photoreceptor was stunning to us
link |
and told us how much we didn't understand
link |
the importance of light on a human behavior.
link |
So how does that finding inform daily protocols
link |
for you or for other people?
link |
I realize you can't leap to always from one paper
link |
to daily protocols,
link |
but if light indeed does control prefrontal cortex,
link |
executive function, learning, stress, and mood,
link |
and let's say I'm waking up each morning and I'm sleeping,
link |
what should I do differently?
link |
That's why we came up with the tripartite model,
link |
because yes, we could think about just adjusting the clock
link |
with lights in and being dark throughout the day,
link |
but that may not be important
link |
for your whole physiological function.
link |
So now if we include these other effects of light,
link |
that's why I prefer to still get a lot of light in the day.
link |
I don't wanna be in very dim light condition
link |
throughout the day.
link |
So even though it doesn't affect your clock,
link |
as you beautifully said, Andrew,
link |
it may affect your mood and learning and memory.
link |
It may affect your alertness level,
link |
which is gonna allow you to learn better.
link |
It may affect your homeostatic drive.
link |
Maybe your homeostatic factor will go higher
link |
so you could sleep earlier.
link |
So it's important to think of light
link |
as stimulating all these brain regions,
link |
which means it's producing more activity,
link |
this is how people think of the homeostatic drive,
link |
that the more active you are,
link |
the more the homeostatic drive is built up,
link |
the better you sleep.
link |
So that's why we came up with the tripartite model,
link |
because as a circadian biologist,
link |
I only thought of light
link |
through the circadian clock affecting behavior.
link |
As a sleep biologist,
link |
they only thought of the homeostatic drive
link |
affecting sleep, affecting behavior.
link |
And for people who study light for vision and other things,
link |
they thought only of the environmental input.
link |
But now if you put them all together,
link |
you get with this tripartite model
link |
where it's really mind-boggling,
link |
and it makes so much sense.
link |
The organism doesn't wanna depend on a single component,
link |
but if you could incorporate these three together,
link |
you could have a beautiful system that is well-adapted.
link |
So let me tell you the sleep-wake cycle, right?
link |
So we know there is a homeostatic drive to affect sleep.
link |
We've had beautiful talks about that.
link |
Which is basically the longer you're awake,
link |
the more you wanna be asleep.
link |
So that's your homeostatic drive.
link |
We've talked about the circadian influence of sleep
link |
and the fact that light-dark cycle affect
link |
the circadian system, which eventually affects sleep.
link |
So these two components are well-understood.
link |
Now the third factor is your direct light
link |
or environmental input.
link |
How much stress, how much light you get from there
link |
also can highly impact sleep.
link |
So even if you have a good circadian and homeostatic drive,
link |
if you're getting light at the wrong time of the day,
link |
or if you're being stressed and thinking,
link |
then your sleep's gonna suffer.
link |
So you have to think of the three together
link |
to have a beautiful sleep-wake cycle.
link |
And that's why we came up with the tripartite motor.
link |
The same thing happens with feeding.
link |
I could beautifully put it to people.
link |
Your hunger, your energy level is measured
link |
by the arcuate nucleus.
link |
Your daily intake of food is, again,
link |
dependent on the SCN and light-dark input.
link |
We found that if food is not available,
link |
there is yet a third input that is not dependent on the SCN,
link |
not dependent on the arcuate,
link |
depending on a completely different brain regions.
link |
So the animal can actually start looking,
link |
or the human can start looking for food when it's scarce,
link |
even at time when they are not supposed to be active.
link |
So that's how the organism think.
link |
They have to evaluate multiple inputs for them to decide
link |
what is the best physiological outcome at that moment,
link |
So I wanna get into arcuate and feeding,
link |
but just to make sure we can keep our hands
link |
around this tripartite model.
link |
So if I understand correctly,
link |
we've got the circadian influence,
link |
then you've also got the drive to sleep.
link |
Actually, one of the ways that I think
link |
that can be best understood is if somebody ever pulls
link |
an all-nighter, they get tired around 11 or 12 or so,
link |
and then very tired around three, four a.m.,
link |
but then even if you stay up,
link |
sometime right around seven or eight a.m.,
link |
your normal wake-up time, you start to feel alert again.
link |
And that's because the sleep drive is extremely strong,
link |
but there's a circadian rhythm that drives wakefulness
link |
Okay, so that's two of the components.
link |
Before we get into the feeding component,
link |
I wanna talk about these direct effects of light on mood.
link |
Okay, Diego Fernandez's data.
link |
And this perihabenular thing.
link |
So let's just, for the moment,
link |
set aside the tri part of the tripartite model
link |
and just focus on what are the direct effects
link |
And the way that I interpret what you've said so far
link |
is that the protocol that emerges from this,
link |
if one is trying to optimize their mood,
link |
is yes, see light, view light, I should say,
link |
early in the day in order to set your circadian clock,
link |
maybe also in the evening as well.
link |
And of course, avoid light at night,
link |
get it as dim as possible.
link |
However, you said it's also a good idea
link |
to get as much bright light during the day
link |
as you safely can in order to improve your mood
link |
independently of regulating your sleep-wake cycle.
link |
And that's a hypothesis.
link |
Here's the problem where it's not gonna be
link |
as satisfying as the circadian,
link |
is that, as you know, this brain region
link |
has been discovered very recently.
link |
The perihabenular region.
link |
We've known about it a long time,
link |
but nobody knew what it did.
link |
So we knew about the habenula,
link |
but that's why the name is confusing.
link |
It's actually not the habenula itself.
link |
It's the perihabenula.
link |
No, near the habenula.
link |
It's near the habenula.
link |
Why don't you just call it the Samaratatar nucleus?
link |
I should have, I don't know why I've done that.
link |
Maybe because if you do that, it's not okay.
link |
Okay, so for herever after, the perihabenular nucleus,
link |
we should probably call it the hotar-
link |
The hotar fernandas.
link |
How about hotar fernandas bursa nucleus?
link |
Okay, this is like nerdy science attribution stuff,
link |
but I'm just gonna call it the hotar nucleus.
link |
Wikipedia, line it up.
link |
Okay, so this structure is taking light
link |
and independent of sleep rhythms and circadian rhythms,
link |
it's driving changes in mood.
link |
How does it do that?
link |
Is this through the dopamine system,
link |
the serotonin system?
link |
We still recently,
link |
we haven't identified this region very well.
link |
We don't know what light does to it.
link |
We don't know how it interacts.
link |
So this is an area that is ripe for discoveries
link |
and we're working on this right now.
link |
But that's why I said it's not satisfying.
link |
This is like the function of sleep.
link |
We know sleep is very important to us,
link |
but we still don't have a satisfying function
link |
of why do we sleep, right?
link |
I see, but the why questions,
link |
I think it's our good friend and colleague
link |
at University of Washington, Russ Van Gelder,
link |
who always says, when somebody asks why,
link |
the best answer is just to say,
link |
I wasn't consulted at the design phase.
link |
Right, none of us really know why.
link |
No, but the point is, maybe I shouldn't have said why.
link |
What is the function of sleep?
link |
It's still very hard to know.
link |
Why would, what is the reason organisms
link |
have to go offline for so long?
link |
You know, people assume it's for repair,
link |
assume it's for learning and memory,
link |
assume all kinds of stuff,
link |
but there is really no clear function for sleeping.
link |
There is no clear function for sleeping.
link |
I mean, if you talk to people, there are hypotheses.
link |
I mean, all we know is that if you don't sleep,
link |
or your sleep is very fractured, you get messed up.
link |
And you could die even, right?
link |
I mean, it's really bad if you don't sleep,
link |
but we don't know what is the function,
link |
what is that sleep have gone to organisms
link |
that couldn't have done with rest?
link |
What if you just could rest without sleeping,
link |
just sit down and rest?
link |
Well, my lab's trying to figure out
link |
whether or not these non-sleep deep rest protocols
link |
can compensate for sleep.
link |
And I mean, obviously sleep is better,
link |
but many people are not getting the sleep that they need.
link |
But okay, so, and if people are sensing
link |
that Samir and I are about to start talking
link |
over each other and arguing,
link |
that's always the goal when we talk, right?
link |
Unlike other scientists I interact with,
link |
when Samir and I get together,
link |
it's considered a successful conversation
link |
if we get into a big fight and then go for a big meal
link |
where I pick the restaurant.
link |
Okay, so let's talk about food and eating and appetite.
link |
You had yet another, yes,
link |
I greatly admire your success in this way.
link |
Yet another incredible discovery showing
link |
that there are direct, excuse me, effects of light
link |
on appetite and feeding behavior.
link |
Maybe you could just summarize those results for people.
link |
Honestly, that paper is the one that allowed us
link |
to come with the tripartite model
link |
because we were thinking completely wrong about it.
link |
We wanted, this experiment, it'd be fun for your audience
link |
to hear why we started this experiment.
link |
Remember that when we discovered the IPRGCs,
link |
we figured if they are the only relay
link |
to entrain the circadian clock,
link |
then you could kill them and have an animal opposite
link |
to the one that we spoke, or a human opposite
link |
to the one that we spoke about earlier,
link |
where instead of having no pattern vision
link |
and have circadian photo entrainment,
link |
we could produce an animal that have pattern vision
link |
but no circadian photo entrainment.
link |
So circadian blind.
link |
Circadian blind, but pattern sighted.
link |
And we succeeded in that.
link |
The problem when you have these animals,
link |
which I've told you many times already,
link |
is that they don't adjust to the day-night cycle.
link |
So doing experiments on them become very complicated.
link |
What is their behavior like if you don't have these cells?
link |
Are they awake and then asleep, awake and then asleep?
link |
They just drift like the humans we've talked about.
link |
They think they're in Las Vegas.
link |
They drift, exactly.
link |
They stay up later every night.
link |
They come either, depends on their clock.
link |
If their clock is shorter, they come in earlier.
link |
If their clock is longer, they come in.
link |
So they're really messed up.
link |
They really don't adjust to the,
link |
if they were in the wild,
link |
they'll be eliminated in a second, right?
link |
There is no way they'll survive.
link |
So me and Diego started talking and we're like,
link |
what if we use non-light entraining agent?
link |
And what is the strong non-light entraining agent?
link |
So we thought that the light-defective animals
link |
will have more sensitivity to food entrainment
link |
because as you know more than me,
link |
this is an area that you've worked really well on.
link |
For vision, if you're image-blind,
link |
your hearing and somatosensory get improved, right?
link |
The lack of vision improves your hearing and sensation.
link |
But we found actually that
link |
if you don't have the light system,
link |
actually you're feeding,
link |
the food ability to entrain the animal
link |
goes completely to the ground,
link |
completely opposite to what we predicted.
link |
So light viewing and feeding behavior
link |
are interacting in ways that support one another.
link |
And that's why we came with the tripartite model.
link |
We figured it's different
link |
than sensation of the environment.
link |
When you sense with vision,
link |
vision and hearing interact,
link |
but your vision is a real full modality.
link |
You want to see, that's what vision want to do.
link |
You want to hear, that's what hearing want to do.
link |
You want to sense, that's what sensing want to do.
link |
But for the circadian system, light, food,
link |
all these entraining agent,
link |
they somehow have to interact to keep a coherent system.
link |
You don't just assume if you remove light,
link |
this one is going to be stronger.
link |
No, they need to know each other's.
link |
The light informs when the animal's going to eat.
link |
Well, what I like about this so much is that,
link |
you know, in the other, in the world outside of science,
link |
in which I don't really exist in,
link |
but that I see a lot of this kind of wellness,
link |
you know, stuff with this,
link |
all this mind-body integration stuff.
link |
It's interesting because people view the body
link |
more as a system, right?
link |
A system of organs that interact,
link |
as opposed to the way that standard science
link |
and medical profession is like,
link |
you work on the liver or your ear, nose and throat,
link |
or heart and lung, or brain, or.
link |
That's a great way of thinking.
link |
But the biology is integrated.
link |
I mean, and so for somebody who's interested
link |
in affecting their eating behavior,
link |
something that you are familiar with
link |
and that we will talk more about your experiences of
link |
how should they use light
link |
in order to adjust their eating behavior?
link |
So now that I've told you about all these interactions
link |
between the different inputs to the circadian clock,
link |
just you think about it as an engineer,
link |
what would be the best thing?
link |
The best thing is to know
link |
when your food times happen in the day,
link |
when should you get light,
link |
and when is your circadian clock in your system, right?
link |
So if you eat at very specific times of the day,
link |
that's another signal that is telling your body,
link |
your clock, you're in a certain time of the day.
link |
So if you're having lunch at the correct time every day,
link |
and you're getting bright light,
link |
now you have two systems that are informing your clock,
link |
your clock is gonna be better.
link |
So regular meal times.
link |
Regular meal times that fit your circadian clock.
link |
So, and in fact, if you do that,
link |
when I started doing this,
link |
and it helped me lose weight,
link |
is that I'm exposing myself
link |
to the right amount of light, dark cycle.
link |
I'm eating at regular time.
link |
You will be not hungry,
link |
let's say you eat at noon.
link |
You will not feel any hunger at 11.45,
link |
and then all of a sudden the hunger jumps.
link |
This is clearly not an energy issue
link |
because it could not be that drastic.
link |
Right, no, the desire to eat is mainly driven
link |
by these cues, these hormone cues,
link |
that are very exquisitely timed to sleep-wake cycle,
link |
but also to light.
link |
And you know, in the wild,
link |
you could imagine why energy level
link |
through the arcuate nucleus-
link |
You should explain to people what the arcuate is,
link |
because I don't think we've done that adequately.
link |
The arcuate nucleus is an area of the hypothalamus
link |
that drives hunger and feeding behavior.
link |
And what we're talking about is the fact
link |
that it's taking cues from your viewing of light,
link |
believe it or not, is impacting your level of hunger.
link |
And this is a non-trivial way
link |
in which your timing of hunger and amount of hunger
link |
is regulated by when and how much light you view.
link |
So let me ask you a couple of practical-
link |
Can I just, this is really, before you ask me,
link |
sorry, Andrew, we said we're going to fight,
link |
but to me, it's the interesting thing to think about it.
link |
In the wild, when you didn't have the availability
link |
of food that we have,
link |
the arcuate plays a huge, important role,
link |
because if you weren't successful in getting food,
link |
then the arc is going to tell you,
link |
look, you have to take risk and go get food
link |
because your energy level is very low.
link |
That's tons of great research about that.
link |
But I think what's missing is the fact in humans,
link |
we're not getting to a situation, most of us,
link |
we're not getting to a situation
link |
where we have low energy levels.
link |
Most of the time, actually, we eat not because we want to,
link |
because we really have low energy,
link |
but because we want to eat.
link |
So I think that's why I feel that the timing
link |
is very important for us
link |
because we always have enough energy level for us to eat.
link |
Well, I mean, I enjoy eating so much that I'll eat
link |
just for the sensation of chewing.
link |
I mean, I enjoy the taste too,
link |
and I enjoy the social aspects when those are a part of it,
link |
but I literally enjoy the physical act of chewing,
link |
Which explains a lot.
link |
Okay, so how regular are you,
link |
or do you recommend people be about meal times?
link |
Because what I'm hearing is that light viewing behavior
link |
is pretty straightforward.
link |
Get a lot of light in the morning and throughout the day,
link |
minimize it in the evening and at night, generally speaking,
link |
for sake of mood and circadian rhythm,
link |
but for sake of regulating timing and quality,
link |
I should also say a food intake,
link |
because people clearly make better choices
link |
about food intake when they are anticipating a meal
link |
and they aren't constantly hungry.
link |
And so the ability to regulate hunger
link |
for particular phases of the circadian cycle
link |
is quite valuable for all people,
link |
not just people trying to lose weight, but all people.
link |
Are we talking about down to the minute?
link |
All right, so 12 noon is my normal lunch, let's say,
link |
So eat around between 11.30 and 12.30.
link |
If that's the time, and it depends,
link |
if you also do multiple meals.
link |
Remember, three meals, that's a decision
link |
that somebody came up with.
link |
Nowadays, fewer people are doing that, I think.
link |
Given our friend Sachin Panda's work.
link |
Right, I mean, so you could have two meals.
link |
You could have very multiple meals
link |
that are distributed across your active time.
link |
I agree with Sachin Panda's work
link |
that try to avoid eating when your system
link |
is supposed to be relaxing,
link |
when you're supposed to be at non-active time.
link |
So, you know, limit your eating
link |
to the active time of your cycle.
link |
And that seemed to be,
link |
and Joe Takahashi is doing some beautiful stuff on this.
link |
That seems to be incredibly important
link |
for aspect of the circadian-
link |
Yeah, I mean, Sachin,
link |
we're referring to Sachin Panda's work.
link |
He wrote a beautiful book called The Circadian Code.
link |
Maybe, Samer, with some luck,
link |
you'll write a book as well,
link |
meaning the world would be lucky to have that book.
link |
But Sachin's data really strongly points to the fact
link |
that liver health, brain health,
link |
metabolic factors and endocrine factors
link |
of various systems and organs
link |
all seem to benefit from having a period
link |
of each 24-hour day in which we are not eating anything
link |
and then eating at very regular times.
link |
Let's talk about eating in meal times
link |
and let's move a little bit away
link |
from the science for the moment,
link |
although we will return to it,
link |
and talk a little bit more about your experience
link |
with eating in meal times.
link |
So you're looking in good shape lately.
link |
I know you've been putting work into it.
link |
We talk a lot and you've been exercising
link |
and you've been eating well, meaning quality food.
link |
You just came back from Jordan
link |
where I'm assuming the food is amazing.
link |
It's the food is amazing.
link |
And honestly, usually I gain a lot of weight in Jordan,
link |
but this time I didn't gain any weight,
link |
which was really nice, so.
link |
Yeah, when I met you,
link |
you were probably about 100 pounds heavier than you are now.
link |
Yeah, 275 pounds, I'm 219 now, it's crazy.
link |
You had a lot of vigor then
link |
and you have a lot of vigor now,
link |
but I know that you undertook a very specific protocol
link |
in order to lose the weight.
link |
Based on your understanding of the circadian system
link |
and of light and appetite and mood,
link |
maybe you could just tell us a little bit
link |
about what that schedule looks like.
link |
And we realize that this is not a prescriptive for everybody,
link |
but you found what worked for you.
link |
Maybe just describe those changes.
link |
I mean, honestly, I followed my circadian cycle, right,
link |
of what we've talked about, right?
link |
So I dimmed the light at night.
link |
I slept at regular hours.
link |
I ate my major food in breakfast and lunch
link |
when I'm really active and I'm really hungry.
link |
And at night, when I avoid dinner
link |
because my circadian system really shuts off at three,
link |
I'm an early person,
link |
like you could give me anything I would eat before three.
link |
After three, nothing appeals to me anymore.
link |
My system is shut off.
link |
What time are you going to sleep
link |
and what time are you waking up?
link |
Oh, so in my case, I should have put this up.
link |
I mean, I go to sleep literally at 9 p.m.
link |
I mean, I literally, five minutes after 9 p.m.,
link |
I'm completely out.
link |
And I wake up between 4.30 and 5.00 a.m.
link |
So if I extend it, I go to 6.00 a.m.
link |
But very rarely, depends on how tired I was.
link |
And that, as I recall, was an important set of changes
link |
for you to be able to regulate your food intake.
link |
Absolutely, because then I'm having very big breakfast
link |
and again, for different people, it's different.
link |
I have a big breakfast at 7 a.m. maximum.
link |
So I have a big breakfast, coffee and all this stuff.
link |
Then I have some simple snack around 10.
link |
Then I have regularly lunch at noon or between noon to one.
link |
Then I have another snack at three.
link |
And the hardest time to regulate the food
link |
is between 12 and three.
link |
This is when I really feel hungry.
link |
This is your equivalent of kind of late evening
link |
So for me, it would probably be between seven and 10 p.m.
link |
And then at night, I'm completely not hungry.
link |
But usually, as you said, the enjoyment of food.
link |
Like when my wife cooks some really beautiful Indian food,
link |
I eat, but I'm not hungry.
link |
And I notice if I eat with that, I usually gain weight.
link |
But if I regulate that at night, I also lose weight.
link |
So there is a combination of all these things
link |
that help you adjust the input of food,
link |
the input of light, the input of the clock
link |
and the drive to hunger.
link |
Yeah, I appreciate you sharing that.
link |
And I want to emphasize that some people
link |
are not hungry early in the day.
link |
They might be late shifted people.
link |
In which case, eating later in the day
link |
will work well for them.
link |
It will work as long as they don't eat early in the morning.
link |
That's just, you have to work with your schedule,
link |
with your active schedule.
link |
Yeah, you and I have been talking about this
link |
offline for years.
link |
I'm glad we're finally having this discussion publicly now.
link |
What we're talking about really
link |
is finding your ideal sleep schedule.
link |
And finding your ideal eating schedule.
link |
And understanding how those two things interact.
link |
And you know, the nice thing, as you said,
link |
finding them out is going to help you
link |
to understand how they interact.
link |
Because we know from the Tripartite model
link |
that they are all interconnected.
link |
And for each person,
link |
they're going to be interconnected differently.
link |
So for each person, you would, you know, for me,
link |
if I exercise at night,
link |
I'm going to mess up my whole system.
link |
So when do you exercise?
link |
Morning works great for me.
link |
I mean, it's amazing.
link |
Morning exercise for me works great.
link |
I tried one time because it was easier for me
link |
to exercise at night before I leave
link |
when the traffic is there from the night.
link |
And I think that messed me up
link |
because I couldn't sleep well,
link |
and I couldn't wake up well,
link |
and that led to more changes in my food.
link |
I gained weight again, actually, believe it or not,
link |
even though I was exercising.
link |
So I think this really makes me think
link |
that you have to think of the Tripartite model
link |
to see where is the best times
link |
and what is the best interrelation
link |
between the different component, as you beautifully said,
link |
between your meal times, your light exposure,
link |
and your sleep that works for you.
link |
Well, thank you for that.
link |
Usually Samir's insulting me today.
link |
He's complimenting me.
link |
I'm going to compliment him right back by saying,
link |
this is the first time that I've ever really understood
link |
how, yes, light can control sleep.
link |
Yes, it can control mood.
link |
Yes, it can impact feeding,
link |
but that it's really about doing the self-exploration
link |
to align those in the way that works best.
link |
And what I'm hearing, tell me if I'm wrong,
link |
but what I'm hearing is that once you understand
link |
what gives you the best sleep-wake cycle,
link |
then you should exercise during the period of time
link |
in which you feel most alert.
link |
And if it works for your schedule,
link |
ideally you would also eat during the time
link |
in which you feel most alert and then stop eating
link |
and stop light viewing behavior as you head towards sleep.
link |
So the only thing I would say that complicates all of this,
link |
and that's what makes me sad, is your light exposure.
link |
No, I'm just kidding.
link |
The people's light exposure, right?
link |
This is what complicates it
link |
because you're not going to be able to figure all this out
link |
if you're shifting yourself out of your comfort zone
link |
by viewing light at the wrong time of the day.
link |
So let's say if you were under an idle natural conditions,
link |
you're a person who would sleep later than me,
link |
let's say we'll sleep at midnight and wake up at 8 a.m.
link |
Let's say you don't eat anything till noon,
link |
and as you said, you eat late in the evening,
link |
then this would be perfect for you.
link |
But now see what happens
link |
if now you include the light component.
link |
Now if you push your sleep from midnight to 4 a.m.,
link |
now you're waking up in the morning
link |
and you're actually really not the morning,
link |
you're working up, sorry, at noon instead of eight o'clock,
link |
and the time where you're not supposed to be hungry,
link |
now you're gonna start eating directly at noon
link |
or something like that, or even delay it.
link |
And now you're shifting your whole cycle
link |
and you don't know if this interaction
link |
between your sleep feeding and the light dark environment
link |
are still gonna be maintained or not.
link |
And that's the problem that people have.
link |
So as I'm hearing this, what I'm realizing is most of us,
link |
probably me included, are messing up at least one,
link |
two, or three of these components.
link |
But that the probe, the way to figure out
link |
what's right for oneself
link |
is to start manipulating light exposure.
link |
And I'm gonna be honest, I'm biased,
link |
because I believe that light is the strongest time giver.
link |
And a lot of people disagree.
link |
Some people think feeding is.
link |
I always thought that light was the primary zeitgeber,
link |
the primary light.
link |
Yeah, but a lot of people think it's food.
link |
A lot of people even sometimes mention social interactions.
link |
And they read the literature?
link |
I totally agree with you.
link |
I mean, my understanding is that light
link |
is the most powerful driver of the things we're talking about.
link |
That's why I think we need to regulate this first
link |
and everything else fits.
link |
And you know, the nice thing is that
link |
your sleep-wake cycle and exercise tell you really bluntly
link |
if you're doing it right or not.
link |
Tell me more about that.
link |
I'll tell you more.
link |
When I shifted my exercise,
link |
honestly, things fell apart like never before.
link |
When you moved from exercising early in the day
link |
to late in the day.
link |
It completely fell apart for me.
link |
I didn't enjoy exercise at night.
link |
My pain tolerance for exercise wasn't as good.
link |
I'm talking with N equals one, and I'm aware of this.
link |
I've never tested this empirically.
link |
But at least to me, it really messed up everything.
link |
I started having problems,
link |
because my body temperature will go up,
link |
and that will affect my sleep.
link |
I possibly was running in the gym with a lot of lights,
link |
so maybe the light was a component.
link |
But for me, exercising in the morning,
link |
it's so much better for me.
link |
But a lot of people can't even think
link |
of exercising in the morning.
link |
So it depends on when you feel comfortable
link |
in your sleep-wake cycle and your exercise.
link |
I think that tells you if your system
link |
is in synchrony with one another.
link |
That's really interesting.
link |
You know, we're good friends.
link |
Our friend Pat Dossett, right, that we both know,
link |
you know, did nine years in the SEAL teams,
link |
and he's one of these people.
link |
He says, you know, he's happy to go for a run or swim
link |
any time between 4.30 a.m. and 6 a.m.
link |
And he'll train in the afternoon, too,
link |
because, you know, he's a SEAL team guy,
link |
and they'll do whatever any time.
link |
That's part of the phenotype.
link |
But he feels best doing that, right?
link |
I'm a mid, I like to exercise mid-morning,
link |
and I'm happy to skip eating until 12 or one.
link |
And I like to go to sleep around 11, 30, 12,
link |
because I'm a normal human being rather than you
link |
who goes to bed at 9 p.m.
link |
What about Pat, actually, I've never asked him what time.
link |
So, Pat's ideal to sleep time.
link |
I've asked him, this would be around 8.30 or 9.
link |
Oh, I sound like Pat.
link |
No, but he has, yes, but he has two young children,
link |
two years old and a newborn,
link |
and so the cycle is disrupted, right?
link |
Yeah, but that's known, right?
link |
I mean, the effect of childbearing,
link |
and I think we could talk about this,
link |
that's more complicated, but that's pretty much, yeah.
link |
Yeah, I mean, I think we need to come up with a new name
link |
for a chronotype, because chronotype implies
link |
that it's just about sleep and wake,
link |
being an early bird or a night owl,
link |
and what we're also talking about is how exercise
link |
and eating match onto those.
link |
And the phase relation between them.
link |
And the phases between different components, as you said.
link |
Because they interact.
link |
Because they interact.
link |
And they don't have to be in the same phase.
link |
Like, let's say my light and food
link |
could be very close to each other's,
link |
your light and food could be different, right?
link |
The phases don't have to be, they can't be plastic.
link |
So you have to find this for yourself.
link |
You may be a person who eats late at night,
link |
exercises late at night,
link |
or you may be a person who exercises early, eat later.
link |
So it doesn't, as long as the phase is good,
link |
that's what you have to find out.
link |
Okay, and if I understand correctly,
link |
when you're talking about phase relationship,
link |
it means you want to lump exercise, feeding, and light for-
link |
And sleep, in a way that,
link |
as a coherent and total system,
link |
makes you feel really good.
link |
Temporally, in a great order.
link |
Yeah, that's, and I think that-
link |
And I could tell you, to me,
link |
is literally getting exposed to sun,
link |
you know, clearly in the morning,
link |
clearly at noon I go out,
link |
I keep my windows in the office completely open,
link |
eating mostly in the early time of the day,
link |
and exercising, and literally at the end part of the day,
link |
I'm literally in a more thoughtful, vegetative state.
link |
Like, I really can't, like after five,
link |
I tell my students,
link |
if you want to tell me anything complicated,
link |
you're wasting your time.
link |
My brain just doesn't function.
link |
So even though I only sleep at night,
link |
but I'm really starting to shut off, ramp down,
link |
really, I mean, it's, you know,
link |
I could send the email, talk about brainless stuff,
link |
but my power, my energy to do powerful stuff
link |
really dropped tremendously.
link |
So all my students who know me very well,
link |
they put the meetings with me early in the morning,
link |
because they know this is when I'm,
link |
so everything for me, and for me, it's very tight.
link |
So it could be different for,
link |
it's very clustered in the morning, it's all tied together,
link |
and literally the remaining part seems to be just a,
link |
you know, vegetative state.
link |
Yeah, you and my bulldog Costello,
link |
who unfortunately passed away recently,
link |
had that in, yeah.
link |
Oh no, I did not, that's so sad.
link |
Sam and Costello were good friends.
link |
Yeah, sorry to break it to you here.
link |
Yeah, he had a good long life and he went easy,
link |
but he had a circadian clock
link |
that basically would just sleep around 24 hours a day.
link |
Minimal activity interspersed every third day or so.
link |
You do have this morning vigor,
link |
and that's, I think other people are going to have
link |
more of an afternoon vigor.
link |
Do you think that this can change across the lifespan?
link |
It's, the rumor is that teenagers naturally want
link |
to sleep in later and stay up later.
link |
Do you think that social rhythm,
link |
or do you think that that's actually biological?
link |
Yeah, that's a tough question.
link |
I mean, it could be both.
link |
One thing that worries me is that it seems that
link |
if anything with age, this morning rigor gets stronger.
link |
You mean you want people to become more of morning?
link |
But why is that worry you?
link |
I think that's good.
link |
Because for me, I'm already a very shifted morning.
link |
I don't want to be one of these 7 p.m.
link |
to 1 a.m. sleepers at some point.
link |
Yeah, on the other hand, it's also kind of nice
link |
because it's quiet and you can get work done.
link |
But honestly, from 4.30 to 7.30, when my wife wake up,
link |
it can be very lonely.
link |
Yes, you achieve a lot, but it's quiet outside.
link |
It's, you know, so I don't want to be at 1 a.m.
link |
Let's put it this way.
link |
You can tell Samra is more social than I am.
link |
But we should touch on that actually.
link |
So your wife is, she follows a different schedule.
link |
And so the social rhythm is important.
link |
I think, what should we do?
link |
How should we conceptualize
link |
and how should we adjust ourselves
link |
according to the social rhythm?
link |
And I honestly love this hypothesis
link |
that people came up with and Pat's kids reminded me of.
link |
Because kids are really gonna disrupt your sleep-wake cycle,
link |
it seems like there is a chrono attraction
link |
that usually people who attract each others
link |
have actually different sleep-wake schedule.
link |
And the idea being is that this allows them
link |
to take care of their kids throughout the day-night cycle.
link |
And have a peaceful marriage.
link |
And have a peaceful marriage in a way, right?
link |
So, I mean, we didn't have kids me and Rachel,
link |
so maybe this is, but it seems like evolutionary,
link |
it makes sense that if you want to protect your kids,
link |
you don't want everybody to be mourning rigor
link |
and then the kids don't have,
link |
so you want the distributed across.
link |
It's a reasonable argument.
link |
I've heard that one of the reasons
link |
that people think that the clock is not exactly 24 hours,
link |
but is 24 hours plus or minus 20 minutes or so
link |
is because we believe that we evolved in clans or groups,
link |
villages, whatever, that we're about 100 to 200 people.
link |
And in order to have protection around
link |
the early morning hours when we're vulnerable to predation,
link |
and in the late night hours that you would want
link |
some individuals of our species to be naturally
link |
more like night owls and some more like early people.
link |
So your theory of parenting is similar in that way.
link |
The social rhythm is a powerful rhythm though.
link |
Meaning if I go out and I'm tired,
link |
let's say I'm tired at like 9.30, I don't want to go out,
link |
like I'm gonna need it.
link |
So can I just say something about that?
link |
I think the social rhythm is powerful at the obvious levels,
link |
like it affects your sleep,
link |
it affects how much you wake up or eat,
link |
but I'm not so sure it's as powerful
link |
as people think on the clock.
link |
Now, eventually it will mess up the clock
link |
because now if you're doing a lot of social at night,
link |
getting enough light, eating at the wrong time of the day,
link |
eventually you're gonna have an effect.
link |
But I don't think that's the social interactions themselves
link |
have been shown to affect your clock very strongly
link |
That's good to know.
link |
Well, for people hearing this,
link |
they're probably getting the impression,
link |
like I'm the night owl and then Samir is the one
link |
that's in bed at nine and then, you know, wakes up at four,
link |
but having attended many meetings with Samir,
link |
I can tell you that he's the party animal.
link |
So let's talk about that.
link |
I mean, let's talk about the fact that you're the partier
link |
who's up until two dancing at these various meetings,
link |
which I've seen, actually a good dancer I'm told,
link |
but what should we do when we do stay up very late
link |
for whatever reason?
link |
Could be because we had to take a midnight trip
link |
to the hospital, unfortunate reason,
link |
or it could be because you're in the presence of people
link |
that you don't see very often,
link |
and you go out for a really nice night out on the town
link |
and you get to sleep around 2.30 or three in the morning.
link |
How should one get back on schedule?
link |
Do you force yourself to then get up and view light
link |
at the normal time that you would get up and view light,
link |
or do you allow yourself to sleep in?
link |
What's the optimal protocol?
link |
I would allow myself to sleep in,
link |
and remember, this is a long-term effect.
link |
This is something that you live with for a long period.
link |
And remember, I told you about the experiments
link |
we did with the mood.
link |
These require two weeks of that light schedule
link |
to cause mood disturbances.
link |
So these don't happen just in a single day.
link |
So this is the way you justify staying out late
link |
every once in a while?
link |
Well, in the meetings you've seen me,
link |
and I've done this for five or six days continuously,
link |
but what you didn't see that when I came back to my home,
link |
it took me two weeks, as if I did a jet lag.
link |
So I really do suffer for two weeks
link |
after doing a six crazy night of staying up at night,
link |
drinking at the wrong time of the day.
link |
So it's not that I'm completely okay with it.
link |
When I go back, everything goes back.
link |
It takes me actually literally two weeks to recover
link |
from the circadian rhythm meeting
link |
that you've seen me partying at at some point.
link |
Which is kind of ironic, the circadian rhythm meeting.
link |
People are totally disrupting the circadian cycle,
link |
but scientists are human beings too.
link |
Right, so I think if you do it at very little occasions,
link |
I think you should not worry too much
link |
that this will have a lasting impact.
link |
And the good news is that if you readjust your schedule,
link |
you could come back to it.
link |
The problem is when you maintain these wrong schedule
link |
for a prolonged team, it becomes chronic,
link |
prolonged periods of time.
link |
That's when you have the problems
link |
and the accumulation of the problems.
link |
So when you have sleeping problem,
link |
you produce metabolic problem.
link |
When you have metabolic problems,
link |
you produce lack of exercise,
link |
and you could see how things can spiral out very quickly,
link |
and then it would be hard to come back to it.
link |
Well, certainly sleep disruption is both a symptom of
link |
and a cause of almost all mental health disorders, right?
link |
And certainly the metabolic syndromes
link |
that people are talking about nowadays and all of this,
link |
it all funnels back to light.
link |
This is what's so remarkable.
link |
And so we have these devices,
link |
and I use my phone and I use my computer,
link |
but do you think that the mere dimming of the screen
link |
or not interacting with screens after,
link |
with say 90 minutes or two hours before bedtime,
link |
according to what we're saying today,
link |
this should have a profound effect on all these factors.
link |
And I really believe it does.
link |
And I, again, I think as Pat has did these inventions
link |
where you get a pouch where you put your phone in a pouch.
link |
So what Samra's referring to is our friend, Pat,
link |
this former SEAL team member that we,
link |
who's also a very impressive person
link |
in the landscape of business and family, et cetera,
link |
a real superhuman from, by any regard,
link |
has this habit of taking his phone
link |
and putting it into a sealed pouch in the evening.
link |
So it's basically-
link |
And in his program, he sends you actually these seal,
link |
you know, patches.
link |
And so that I think is a great idea
link |
because not only it will take away the light from you,
link |
but it also take away the distraction
link |
because you wanna repair and recover and sleep does that.
link |
And if you have your phone dinging all the time
link |
or the light flashing from it,
link |
you're just not getting enough sleep
link |
and you're causing yourself major problems.
link |
I never asked you this,
link |
but I realize now that I should have long ago,
link |
but I'll ask you now,
link |
why and how did you get into all this stuff?
link |
Yeah, I mean, honestly, I, first of all,
link |
I wanted to become a, you know,
link |
I wanted to study genetics
link |
and I knew I wanted to do PhD in genetics,
link |
but I only got accepted in one university at the time
link |
and I joined the learning and memory lab.
link |
And I liked learning and memory.
link |
At the beginning, I worked in the snails
link |
on a plesia californica
link |
and started looking at learning and memory,
link |
but then the same lab was looking at these daily variation.
link |
I was really struck.
link |
Like you never think about it outside of science.
link |
It really struck me that organisms can measure day,
link |
biologically, that was very shocking to me.
link |
And I just really got attracted
link |
and I wanted to see why does this happen?
link |
What is the effect of different times of day?
link |
And I just stuck with it.
link |
It's just, it was mind blowing for me,
link |
who was in medical school
link |
that I've never heard about it before.
link |
You know, it's really amazing medicine.
link |
I think still now we are very good
link |
at looking at stuff spatially,
link |
but we're very bad at looking at temporal aspects.
link |
So we always, you know, like to see images,
link |
static images, spatial information.
link |
Take an X-ray, measure a temperature,
link |
measure a blood pressure.
link |
Exactly, but we don't think of temporal.
link |
And you know, you talk to John Huganash right now
link |
and he's telling you the importance of chronomedicine
link |
or chrono pharma, pharma two, whatever the word is.
link |
And it just, it really just getting the drugs
link |
at the right time of the day
link |
is gonna be essential for our health.
link |
Do you think that's gonna come from using better trackers
link |
like aura rings, whoop straps, these kinds of things?
link |
I love the trackers,
link |
but I think there's even more exciting discoveries.
link |
Now you could take a single blood sample
link |
and measure many biological components
link |
and figure where you are in the circadian clock,
link |
something that was very hard to do before.
link |
So if you have a marker to know where you are in the clock,
link |
you could actually understand more the effect
link |
of everything, exercise, feeding, light input.
link |
What is the marker?
link |
So there are some papers from, what's her name,
link |
Phyllis Zee and from Haim Kramer,
link |
where they measure multiple RNAs
link |
that are known to tell you what phase of the clock is
link |
or multiple proteins or biological reactions.
link |
And depending on a combination of factor,
link |
not a single factor,
link |
you could tell where you are in the circadian clock.
link |
So they could, instead of just measuring temperature
link |
or melatonin, just one measurement.
link |
And melatonin specifically is also complicated
link |
by the fact that melatonin is affected by light.
link |
And temperature, your temperature and sleep
link |
can be easily dissociatable, right?
link |
When you travel across different times on your sleep
link |
at different times in the temperature cycle.
link |
So having multiple components measured
link |
will give you a better determination of your circadian phase
link |
and understanding your circadian phase in humans
link |
will tell you what is the effect
link |
of giving certain drugs
link |
at certain times of the circadian phase.
link |
So in the future, this is gonna be studied
link |
at a much higher level when you can determine the phase
link |
in relation to all the other stuff.
link |
It's striking to me that in all animals, besides humans,
link |
if they deviate too much from the appropriate exposure
link |
to light and light-dark cycle,
link |
they essentially don't mate and or die
link |
and or get killed off.
link |
But in humans, we are able to override that
link |
at least to some extent.
link |
But the ways in which we suffer appear to be things like
link |
obesity, metabolic syndromes, reproductive syndromes
link |
that accompany the other syndromes, endocrine syndromes
link |
and mood and depressive disorders.
link |
Is there any effort at the level of the nationally
link |
or laboratories that you're aware of
link |
to try and use light in order to improve mood
link |
and mental health?
link |
I mean, honestly, this is my mantra.
link |
This is the thing that I think people,
link |
because I say, don't take a pill, take a photon.
link |
I mean, you take pills, it's important.
link |
I'm just making it that really,
link |
we have an opportunity right now
link |
with the incredible advances of LED lights,
link |
of changing spectrum of light, of regulating intensities.
link |
And just for simple changes,
link |
you could really improve sleep-wake cycle, productivity,
link |
and still you could actually get more done
link |
because as we've talked about,
link |
when you have all these messed up,
link |
now you have to sleep more, but your sleep is fragmented.
link |
It's not very good.
link |
And you can't focus when you use it.
link |
And you can't focus when you don't have alertness
link |
when you need the alertness.
link |
So having all these could allow you to do even more
link |
actually at the end than less.
link |
And that's the exciting part of it.
link |
One of the questions I get asked most often about
link |
I think there's a lot of self-prescribed
link |
as well as clinically prescribed ADHD.
link |
People are having a tremendously difficult time focusing
link |
and not just because they're sleepy,
link |
they just can't seem to anchor their attention.
link |
And there could be multiple reasons for this,
link |
but there are now several clinical trials ongoing
link |
using light to try and anchor people's attention
link |
and mood and wellbeing for sake of focus.
link |
And I think that while I love this saying
link |
that you mentioned, take a photon, not a pill,
link |
and with due respect to the need for pharmacology
link |
for certain people, I think most people
link |
just haven't really dialed in their relationship to light
link |
in a way that allows them to rule out
link |
whether or not they need medication.
link |
That's the best way to put it.
link |
I can't add to that.
link |
Let's talk about jet lag, but not in the context of,
link |
okay, if somebody's traveling from Europe to Japan
link |
or from the East Coast, because that varies tremendously,
link |
I mean, there's as many different variations
link |
on travel as there are individuals out there
link |
and with goals and jobs, et cetera,
link |
but rather let's talk about what are the two or three things
link |
that people can do to adjust their schedule quickly.
link |
Yesterday, I called you and said, look,
link |
I know somebody who's traveling six hours.
link |
I won't even mention in which direction
link |
because I don't want people to anchor to that example.
link |
And you described some very simple tools of viewing light
link |
a little bit earlier than normal
link |
and getting on the local food schedule, et cetera,
link |
that would allow them to shift more quickly.
link |
And the reason I want to have this conversation is yes,
link |
for the travelers and for the shift workers,
link |
but mostly because of the fact that you've proven
link |
again and again that people are disrupted
link |
in their circadian behavior at home.
link |
So what are the, aside from what we've already talked about,
link |
how can one adjust quickly to a new schedule?
link |
Like let's say fall classes are starting,
link |
you start a new job or you have a baby or a puppy
link |
or whatever, what is the best way
link |
to shift the clock quickly?
link |
So it's very simple as we've talked yesterday.
link |
So imagine you're in the outside with no industrial light.
link |
If your body thinks you're in early evening
link |
and you see a bright light, what does this tell you?
link |
Oh, wait, this is not early evening yet.
link |
It's still early afternoon or late afternoon.
link |
So I have to delay my clock to go back to late afternoon.
link |
So if you get light early in the evening,
link |
it delays your clock.
link |
Meaning that makes you want to go to sleep later.
link |
Yes, it delays your clock.
link |
So you're in New York, right?
link |
People in Italy have an advanced clock
link |
because they are six hours ahead of us.
link |
So if you're in New York and you get light early
link |
in the evening, you delay even further from Italy.
link |
So now you're delaying away from Italy.
link |
Now, the same thing happens.
link |
Let's say you thought dawn came up
link |
and you thought it's already dawn,
link |
but it was, let's say, three o'clock in the morning
link |
or four o'clock in the morning.
link |
And then you get a bright light and you say,
link |
oh, wait a minute, dawn is not up yet.
link |
So I should advance my clock.
link |
Or I'm at night, but I'm getting bright light
link |
so I should run because dawn is already up.
link |
So then later in the night, later in your night,
link |
and actually it just happens that the humans,
link |
you get a temperature in the day or later in the night,
link |
low temperature in your body.
link |
After that, light start advancing your clock.
link |
So if you want to go to Italy,
link |
instead of getting light early in the evening,
link |
you want to get light after the temperature low.
link |
So you could advance your clock even before you go to Italy
link |
and you're catching up to the Italians just by using light.
link |
It's as simple as that.
link |
So you could do it for every region.
link |
You could calculate how much they are advanced of you.
link |
You could know how much these light shifts happen per day,
link |
and you can calculate what you need to do,
link |
very simple math, to adjust either in direction of delaying,
link |
if you're going from New York to California,
link |
you want to delay your clock,
link |
or advancing if you're going from New York to Italy.
link |
So in order to make that a visual,
link |
and because a lot of people are listening to this,
link |
not looking at it on video,
link |
we will put a zero-cost downloadable figure of this
link |
on the Hubermanlab.com website related to this episode.
link |
But I think I can summarize it in language as well.
link |
If I understand correctly, what you're saying is,
link |
if your typical wake-up time is, say, 7 a.m.,
link |
then your low point in temperature
link |
probably occurs somewhere around 5 a.m.
link |
And if you view light right around then,
link |
it's going to essentially advance your clock.
link |
Because then your body thinks,
link |
oh, it's 7 o'clock, so it'll advance your clock
link |
by one to two hours.
link |
But if I were to view light, say, at 3 a.m.,
link |
then it would probably delay my clock.
link |
Yeah, so, and then let's say I land in a new schedule.
link |
I want to adjust to a new schedule.
link |
Let's say I didn't manage to do anything
link |
with my light viewing before I went,
link |
and I didn't anticipate the trip.
link |
Suddenly, I'm on a new schedule, okay?
link |
I was told that one of the ways to help shift the clock
link |
and to avoid gastrointestinal issues
link |
is to eat on the local schedule,
link |
to start basically behaving like a local,
link |
even though your circadian clock
link |
will take a little bit of time to catch up.
link |
But you have to remember the light, right?
link |
So let's, now that we explained it very simply,
link |
let's take a very simple example, right?
link |
New York to Italy.
link |
That's a simple example.
link |
New York time, Italy time, six-hour difference, right?
link |
So let's say you fly from New York at night.
link |
You reach Italy at eight o'clock in the morning.
link |
What is the time in your New York time?
link |
Although you reach-
link |
So when you land Italy,
link |
you want to avoid light like the plague.
link |
Yeah, you could eat,
link |
but you really don't want to get a light.
link |
Right, because otherwise it's going to delay you.
link |
It's going to delay you.
link |
It's going to send you to California
link |
instead of sending you to Italy.
link |
Right, and so this is such a key point.
link |
If anyone's confused about this,
link |
we will put some diagrams up,
link |
but what Samir's saying is so crucial.
link |
Just because getting bright light in your eyes
link |
early in the day is really beneficial when you're at home.
link |
When you travel to a new time zone,
link |
you have to take into account what your body thinks,
link |
you have to take into account
link |
where your body thinks you are.
link |
And so if you're looking at the Italian sunrise,
link |
having just flown from New York to Italy,
link |
and you didn't prepare for that trip
link |
by waking up a little bit earlier in anticipation.
link |
Multiple days, yeah.
link |
And you view light at two a, excuse me,
link |
at six or seven a.m. Italian time.
link |
Beautiful Italian sunrise.
link |
You are going to delay your clock.
link |
You're going to basically throw yourself back to California,
link |
but you are in Italy.
link |
You're going to throw your biology back to California
link |
and you are going to be up
link |
in the middle of the Italian night
link |
and you're going to be miserable.
link |
I'll tell a brief anecdote
link |
because I called Samir in desperation a few years ago.
link |
I traveled to Abu Dhabi, NYU Abu Dhabi to give a seminar.
link |
12 hours out of phase, it's a 12 hour flip.
link |
And I thought I could just muscle it.
link |
I thought I'll get up,
link |
I'll just view sunlight when the sun comes up.
link |
And I fell apart mentally and physically.
link |
And Samir came to my rescue.
link |
I said, I don't know what to do.
link |
And he said, go to the gym,
link |
went at the local dawn,
link |
and then view sunlight starting the next day.
link |
And that basically got me onto schedule.
link |
So I used food and exercise to adjust myself
link |
because my light viewing activity
link |
was just completely out of whack.
link |
Yeah, I mean, and we talked about other details.
link |
So you have to calculate it,
link |
but you're absolutely right.
link |
I mean, it's very important
link |
to avoid getting the wrong light information
link |
when you're trying to adjust your body
link |
because otherwise it shifts you to the other side.
link |
Well, you are one of these people that has such vigor.
link |
It's one of these things
link |
where having known you all these years,
link |
you have a tremendous capacity for work
link |
and for soccer and for arguing, respectful arguing.
link |
And, you know, sometimes, you know-
link |
It's getting worse with age.
link |
Yeah, well, we could talk about that offline,
link |
but I think a lot of your vigor
link |
and a lot of your ability to work hard and focus
link |
and really do so many things at an impressive level
link |
is because you think about these issues
link |
and you think about when you're going
link |
to be optimal for focus,
link |
when you're going to be optimal for exercise,
link |
when, and the when is the key.
link |
And I think a lot of people live in the landscape
link |
of feeling like there's something broken inside them
link |
because they can't focus.
link |
It's subconscious, right?
link |
Remember, it's all subconscious, these effects.
link |
And you're absolutely right.
link |
Now, honestly, joking aside about age,
link |
I really agree with you that I think part of the reason
link |
I'm continuing to be able to do this,
link |
that I really think about it
link |
and I make sure that I keep everything aligned.
link |
And that actually helps me a lot.
link |
Like I don't suffer in sleep.
link |
I don't suffer in waking up.
link |
I never use a timer to wake up.
link |
I mean, people say, aren't you scared?
link |
Like you have to give a lecture at eight or 7.30.
link |
Honestly, I was like,
link |
there is no way I'm going to go beyond that.
link |
It just, even if I try,
link |
I can't sleep beyond 6 a.m. in my regular times.
link |
It's just, it's not going to happen.
link |
By 4.30, my eyes are wide awake and I'm in bed.
link |
It's just, system is so aligned, it works.
link |
A lot of times people will say,
link |
how come I go to sleep?
link |
I fall asleep fine,
link |
but then I wake up at three or four in the morning
link |
and can't fall back asleep.
link |
Is it possible that those people
link |
were supposed to go to bed at 8 p.m.?
link |
I mean, it is possible.
link |
It is also possible that sometimes people will wake up
link |
and go back to sleep.
link |
But yeah, I mean, it is possible,
link |
or it's possible that their clock is completely misaligned,
link |
that they are getting maybe a nap time at night
link |
when they are supposed,
link |
and then they possibly feel so sleepy in the day.
link |
So all these are possible combinations.
link |
Well, that's an interesting idea and considered.
link |
So what they think is their sleep,
link |
their body is so out of whack with the light dark cycle
link |
that it's actually a nap.
link |
Or the weaker part of the sleep.
link |
I mean, you see this when you travel
link |
to different time zones before you adjust.
link |
You go to sleep really well,
link |
but two hours later you're fully up.
link |
If you were so tired and this is your regular sleep,
link |
there's no way you're gonna wake up in two hours.
link |
So then you feel very sleepy later in the day
link |
or something like that.
link |
So it depends on how your whole system
link |
is aligned to the environment.
link |
That's a very interesting idea.
link |
I think that's gonna resonate with a lot of people.
link |
I wake up every morning around three or four.
link |
I generally use the bathroom
link |
and then I fall back asleep very deeply.
link |
Doesn't seem to disrupt my daytime wakefulness.
link |
And I think a lot of people obsess over that waking up
link |
and worry there's something wrong.
link |
Provided they can go back to sleep, it's okay.
link |
If you can't go use the bathroom, go back to sleep,
link |
that should not be a problem.
link |
Maybe some people when they go to use the bathroom,
link |
they use very bright light
link |
and then they get an alerting signal.
link |
So if you, maybe that could be as simple as that,
link |
Maybe when you wake up, you put tons of light
link |
or you start reading your iPad.
link |
So there's all these combination
link |
that we still don't know about
link |
that could be affecting their sleep wake rhythms
link |
and their sleep maintenance.
link |
Do you use melatonin or do you take melatonin?
link |
I don't need it to be honest.
link |
In my case, there is no reason to use it
link |
because I could guarantee you that by maybe eight o'clock,
link |
my melatonin has already started to go up.
link |
And by the time I sleep, my melatonin is very high
link |
because I don't use a lot of lights after sunset.
link |
And light inhibits melatonin.
link |
And life really blocks melatonin level.
link |
You hear this myth that the pineal gland
link |
calcifies as we get older.
link |
Is that, do you know anything about that?
link |
I mean, I've heard about that, but I don't know what does,
link |
I mean, there is not very clear evidence
link |
that affects the sleep.
link |
I don't know much about it, to be honest.
link |
The evidence that I've seen is that yes,
link |
there's some calcification around the pineal,
link |
just because of where it sits in the brain.
link |
It's close to some bony structures,
link |
but I don't think there's any evidence
link |
that it has negative effects.
link |
I mean, if you still have, you could measure melatonin
link |
and that should tell you if it has any,
link |
it's such an easy thing to do.
link |
I think this is more of a internet wellness thing
link |
that got outside the cage.
link |
I think you're absolutely right.
link |
Yeah, it sounds terrible calcification
link |
of the thing, right?
link |
The hard thing, right?
link |
Let's talk about seasonality a little bit.
link |
I learned, and I don't know if this is still true,
link |
but that most suicides occur in April, in the spring.
link |
I think there's a poem that says,
link |
April is the cruelest month, I think is the poem begins.
link |
Are there data that suicides are more frequent
link |
at particular times of year?
link |
And if so, is the spring that time of year?
link |
Yeah, I mean, a lot of people talk about this.
link |
And one of the hypothesis is that the winter months
link |
that are very bad for mood
link |
make people not wanting to do anything.
link |
And they get into such deep level of depression
link |
that when the sun comes up,
link |
they get actually the energy to act on their depression,
link |
which sounds really terrible, and it is terrible.
link |
So that's the idea that the lack of light
link |
throughout the winter caused them to go into such depression
link |
that they don't feel like doing anything.
link |
And when the light comes in with rigor in the spring,
link |
it gives them that,
link |
after all the depression they suffered,
link |
gives them that push to take that sad final act, I guess.
link |
What other seasonal effects have been demonstrated
link |
Yeah, I mean, I think in humans,
link |
it's not very clear because we don't think about seasonality.
link |
But if you start thinking about us,
link |
I think we go through major seasonal changes.
link |
I think our eating pattern change across the year,
link |
I could tell you that me thinking about this,
link |
there's a clear changes that happens to me across the year.
link |
But for animals, this is really essential.
link |
Because for animals, they have to time their mating behavior
link |
was when they deliver their progeny
link |
in the most abundant amount of food.
link |
And artificial light is causing major disruption
link |
because if you change the way these animals
link |
are receiving the light information,
link |
they either start mating much earlier or much later,
link |
and their numbers dwindle,
link |
and they get into the dangers
link |
of really completely getting eliminated or extinct.
link |
Well, human birth rates are definitely going down.
link |
I mean, in the U.S. in particular.
link |
Some areas, not others.
link |
Not others, right.
link |
But are there other effects of seasonality on humans
link |
that we are aware of?
link |
Honestly, like you could see it,
link |
honestly, you could see it perfectly, I think,
link |
I mean, you could talk to people who live in.
link |
Sure, they get seasonal depression.
link |
Well, seasonal depression is one,
link |
but actually when you start asking them questions,
link |
they tell you like in the winter,
link |
they barely could wake up,
link |
they barely have the energy before even depression.
link |
Even people who don't get seasonal depression,
link |
they'll tell you our energy level is lower,
link |
our ability to go to work is not the same.
link |
And in the summer, most people actually sleep very little.
link |
They tell you we really can,
link |
we feel like we're manic, we have all this energy,
link |
and not in a negative way, in a funny way, right?
link |
I mean, but if you wanna sleep,
link |
we have to put this curtain.
link |
I think in these situations,
link |
you could really appreciate the seasonality of humans.
link |
I think we kind of destroyed our seasonality
link |
because we don't get exposed to that much natural light.
link |
We have all this artificial light.
link |
But I think, honestly,
link |
one of the things that is gonna happen,
link |
if they follow your recommendations
link |
about giving light at the same time,
link |
giving food, giving exercise.
link |
Wait, let's be clear, those are your recommendations.
link |
Well, I mean. No, I'm just fair attribution.
link |
What I'm saying is that this is gonna cause them
link |
to also experience some changes across the season
link |
because now, they're gonna see the sun differently.
link |
If you're gonna go out in the morning,
link |
in the summer, you're gonna get a much brighter,
link |
that's why I don't like the change in time.
link |
I know people think, oh, because you're biased,
link |
Wait, wait, wait, sorry.
link |
The change now, are you talking about daylight savings?
link |
Daylight savings, it's such a bad idea
link |
because it disrupts that rhythm that you're having.
link |
Because I think your body, if you keep that rhythm,
link |
you will see the whole seasonality.
link |
And I look at it from a different aspect than other people.
link |
It really, and people say I'm biased
link |
because I'm a morning person, and it may be true.
link |
But there's situation.
link |
Secret conspiracy about morning people.
link |
Yeah, but there is, if you think about it, Andrew,
link |
there is a situation where you're getting light
link |
perfectly well, and then all of a sudden,
link |
they delay it by one hour.
link |
And then, even though it's the summer,
link |
your body now, if you're still not adjusting,
link |
think, oh, wait, what happened?
link |
What kind of happened?
link |
Well, I'm glad you're bringing this up
link |
because I always thought, what's the big deal?
link |
One hour shift, spring forward, fall back.
link |
It's so hard to adjust to one hour action.
link |
But this goes back to the beginning of our discussion.
link |
It's not just one hour.
link |
Because it's one hour across that one day,
link |
but there's this cumulative effect on the clock
link |
and these three elements of your tripartite model.
link |
The homeostatic sleep and the direct effects on mood.
link |
And when it's so close, it's sometimes hard to figure out
link |
how to adjust it perfectly because, you know,
link |
we're already sleep deprived in our society.
link |
And then you shift it by, you know,
link |
so it just, it all accumulates and it has no benefit.
link |
Well, you work at a major government organization,
link |
National Institute of Mental Health.
link |
Why don't we campaign for-
link |
Honestly, I have no idea.
link |
I mean, it makes no sense.
link |
No, I'm saying, why don't we go campaign?
link |
Yeah, I would love to.
link |
I mean, it makes no sense to have the summer light
link |
The light goes down where I live in Baltimore at 9 p.m.
link |
And then all of a sudden, when you really want to
link |
see the light longer in the day,
link |
you now shift the other way.
link |
And now it goes all of a sudden at 6 p.m.
link |
Why do you do these drastic changes?
link |
Well, let it blend across the whole season.
link |
You know, yes, later, earlier at night,
link |
but it's at least consistent.
link |
It goes in a very consistent manner.
link |
I just don't understand why they do this.
link |
It makes no sense.
link |
Well, I think that the reason they do it
link |
is because they don't understand the biology.
link |
Because one hour seems trivial,
link |
unless you understand the repercussions
link |
of that one hour shift.
link |
Because what's also clear now,
link |
based on what you're saying,
link |
is that that one hour shift is taking you
link |
out of alignment with the natural light dark cycle
link |
in exactly the wrong direction.
link |
It's pushing people to get even later in the summer
link |
when light is going to push you later anyway.
link |
It doesn't make sense.
link |
You put it beautifully.
link |
I just rambled and this is new.
link |
No, no, you made it clear.
link |
I mean, it's like literally it made you,
link |
it made people who are having problem
link |
having an advanced sleep rhythm because they are delayed.
link |
Now you give them this hour to make them even more delayed.
link |
You push them even later in the day and night cycle.
link |
It just doesn't make sense at all.
link |
I think 2022 should be the year
link |
that we abolish bad daylight savings.
link |
That would be the day for me, honestly.
link |
Well, also if it has a positive effect on the,
link |
what is essentially an epidemic of mental health issues
link |
and other issues related to
link |
improper interactions with light,
link |
that I think is a well worthwhile cause.
link |
And we can explore.
link |
So for once we're going to fight with some,
link |
with another group, a common battle
link |
as opposed to with one another.
link |
I mean, the circadian people, honestly,
link |
to give them credit have been trying for years
link |
to abolish daylight saving.
link |
Yeah, the problem is they all go to sleep at 9 p.m.
link |
and wake up at 4 a.m. so we never see them.
link |
No, the circadian community has done an amazing job
link |
of figuring out what we need.
link |
And then the challenge of course is
link |
making sure that people get what they need
link |
and making sure that at a societal level,
link |
we're not vaulting ourselves into the wrong direction.
link |
The biggest problem is that the late waking people,
link |
they think that really,
link |
and I'm going to try to put it in a better way now,
link |
they think, oh, because you're a morning person,
link |
you want to see the sun early,
link |
so you want me to suffer it dropping late.
link |
But that's not the case,
link |
because what happens is when they shift it back
link |
after the daylight saving,
link |
now they're going to make you suffer really badly
link |
because now it's going to be earlier.
link |
Right, in the fall.
link |
In the fall when there's not enough light.
link |
If they keep it the same way,
link |
so try to convince them that actually this at the end
link |
causes more trouble when you need the light
link |
for your late schedule in the fall
link |
when they shift it back.
link |
Then they say keep it daylight saving all the time.
link |
And that has been proven.
link |
Like people have done studies
link |
that literally two areas close to each other's
link |
and areas that were the whole year on daylight saving
link |
has much more problems,
link |
even in cancer rates and depression.
link |
So you don't want to do that.
link |
So that's what trying to convince people
link |
that you need to prevent that switch
link |
and you don't need daylight saving at all.
link |
That's where the problem happens.
link |
I had not thought about that,
link |
but yes, you late risers that in the fall,
link |
when they fall back, as they say,
link |
spring forward, fall back, you dial back the clock.
link |
It's really compounding the problem that already exists.
link |
And it's really nice if you keep it consistent.
link |
In the spring, you get the equinox
link |
and then the days start going up
link |
and then even in the summer start going down
link |
and then the fall, you get the other equinox and go back.
link |
So it's very symmetrical, right?
link |
It goes into short day, longer, long, long, long,
link |
then short day again.
link |
But now you're getting these bumps
link |
in both sides of the spring and fall.
link |
Why would you do that?
link |
Something that is beautifully symmetrical,
link |
beautifully smooth, you're putting bumps into it.
link |
Well, and not just beautiful because it's there,
link |
I mean, essentially this is the system we evolved in
link |
for hundreds of thousands of years.
link |
Even apart from the exact equator,
link |
every part of the earth has seasonality.
link |
I want to briefly touch on something
link |
which is individual and genetic variation
link |
in sensitivity to light.
link |
So not chronotype, but first of all, a very basic question.
link |
Do people with light eyes, light colored eyes,
link |
are they more sensitive to light
link |
than people with darker pigmented eyes?
link |
I mean, honestly, it makes sense they will be more
link |
because if you think of my dark pupil,
link |
it's blocking more light.
link |
So if you have light pupil, yes, for vision,
link |
it may not be very obvious,
link |
but for something that is measuring the amount of light,
link |
you're getting more light than me.
link |
So you'll probably need less light to be effective
link |
as somebody who's darker.
link |
And that maybe could explain why sometimes lighter people
link |
say I don't want to go into very bright conditions
link |
because it's really bright.
link |
Yeah, I can't even be at a cafe
link |
without one of these reflective tables, like a metal table,
link |
unless I have very dark sunglasses on.
link |
It's so bright it's painful for me.
link |
Whereas some people like you,
link |
we've sat outside and had meals and you're like, fine.
link |
I assumed it was kind of Jordanian toughness versus, you know.
link |
It's really the pupil blocks more light.
link |
So I think it is possible that it's as simple
link |
as the pupil blocking more light can have sensitivity.
link |
But your question also goes deeper.
link |
Are there more sensitivity differences?
link |
And my understanding would be,
link |
I would think that it may be depends
link |
on how effective your cells are in responding to light,
link |
how healthy your IPRGC's are.
link |
So I would, but there's not many studies to show that.
link |
What is really clear that is happening
link |
is that patients with bipolar,
link |
they seem to have different sensitivities to light.
link |
So it seems that at least people
link |
who have psychological changes,
link |
they may have differences to the sensitivity of light.
link |
Are those differences in a particular direction?
link |
I don't remember the exact.
link |
We'll have to, we can look it up.
link |
And people have heard me say this ad nauseum
link |
to the point where they actually roll their eyes,
link |
but you know that these are the only two pieces of brain.
link |
I'm pointing to my eyes folks
link |
that are outside the cranial vault.
link |
They are two pieces of brain
link |
that it basically inform the brain
link |
about whether or not to be alert or asleep.
link |
But you can imagine that those two little pieces of brain
link |
that we call eyes would have genetic variations.
link |
Of course, eye color is genetically modular.
link |
Is that determined?
link |
That there would be genetic variations
link |
based on whether or not your ancestry evolved
link |
near the equator or further from the equator, right?
link |
I mean, you see more blue eyes in Scandinavia
link |
than you do in the equator. Absolutely.
link |
I mean, it's the lack of light
link |
that said you need less inhibition
link |
because there's not enough light, right?
link |
So that's the idea of the change in color.
link |
So yeah, I totally agree with you.
link |
I mean, I think this is an area that will be studied later
link |
and will be empirically determined.
link |
The problem we have in this field right now,
link |
which I think is the biggest problem,
link |
is we don't have a way to measure
link |
the IP RGC sensitivities in humans.
link |
So we still, like it's easy to measure your rod cone function
link |
if you go to an optometrist.
link |
They measure all the details, right?
link |
Contrast detection.
link |
You look at the chart, you look at the Snellen chart,
link |
you look at the letters at the DMV, yeah.
link |
But for the non subconscious,
link |
we still don't have a good measuring systems
link |
to figure out what is Andrew's sensitivity?
link |
What is Samer's sensitivity?
link |
What is this person's sensitivity?
link |
And I think we're starting to work on something like that
link |
to hopefully develop these techniques,
link |
but till we develop them,
link |
it's gonna be very hard to figure out
link |
if there is a sensitivity difference,
link |
how do they relate on men and women,
link |
you know, dark and light and all that,
link |
you know, normal versus psychologically effect
link |
and stuff like that.
link |
And every time you talk, I learned so much.
link |
It's like in the best way, the best sense of the term,
link |
it's a waterfall of knowledge.
link |
As a final question, I have a question about sensitivity
link |
of a whole other kind.
link |
And that's the sensitivity to spicy food.
link |
Now, the reason I'm asking this question,
link |
what seemingly out of the blue is that
link |
I made the mistake once of having Samer cook for me.
link |
And I said, not too spicy.
link |
And he said, okay, not too spicy.
link |
He actually said, okay, not too spicy.
link |
And it almost killed me.
link |
Like it was like two or three days.
link |
So you know a lot about biology
link |
outside the visual system, light, et cetera.
link |
You've been around a while.
link |
Are there known genetic or inherited
link |
of any kind sensitivities to spicy food,
link |
to things like red peppers and capsaicin?
link |
Because what you call mild,
link |
my friend almost put me into the hospital.
link |
I think this is similar to you swimming in the ocean
link |
and I need to get developed.
link |
I like cold water swims and Samer's not a fan,
link |
but that's going to change.
link |
That's going to change.
link |
Before I met Reiji, I was like you.
link |
And once I started eating a lot of spicy food,
link |
I lost touch of how spicy my food is.
link |
So I nearly killed you, Andrew, and I apologize.
link |
So basically what you're saying is that marriage
link |
Toughened me up, exactly.
link |
Maybe that's the solution.
link |
That's what you need, yeah.
link |
Samer, this has been an amazing march
link |
through the importance of light,
link |
not just for regulating sleep and wakefulness,
link |
but also for food timing, the interactions with mood,
link |
the interactions with exercise.
link |
I'm certain that people are going to start thinking
link |
about how to change their relationship with light
link |
as a way to anchor everything that they do
link |
and that's important to their health.
link |
And I just, on behalf of all of them
link |
and just directly from me as your friend
link |
and as a colleague for many years now,
link |
I just want to say thank you
link |
for the incredible work you're doing
link |
and for sharing it with us.
link |
Thank you so much.
link |
And actually now thinking about all of this,
link |
and you said, I should write a book,
link |
I should write a book and call it the tripartite model.
link |
I think that would put all these components together
link |
would be very interesting to do at some point.
link |
You should write a book.
link |
You should write, they'll probably try and change the title
link |
to like Food, Mood and You, you know, or something because,
link |
but you can put in little print on the tripartite model
link |
or whatever, but regardless of what it's called,
link |
you absolutely should write a book.
link |
And so if you'd like Samir to write a book
link |
or if you'd like to learn more about him,
link |
let's talk a little bit about where people can find you.
link |
Your laboratory is at the National Institutes
link |
He is head of the Chronobiology Unit,
link |
all these things that I've mentioned earlier,
link |
but you are active on Twitter and Instagram.
link |
So what is your Twitter handle?
link |
It's at Samir Hattar.
link |
And we will provide a link for that in the show notes.
link |
Sorry, yes, at the Twitter at Samir Hattar
link |
and I think the same for Instagram, yeah, actually.
link |
And Samir has been coaxed onto Instagram.
link |
So he does post from time to time,
link |
mostly pictures of food that is incredibly spicy,
link |
but also information about chronobiology.
link |
He comes on for an Instagram live every once in a while
link |
with me and so definitely give him a follow there
link |
And I'm sure that he'll be happy to answer questions
link |
and entertain any and all discussions about chronobiology.
link |
Absolutely, yeah, and light, yeah.
link |
Great, thank you, Samir.
link |
Awesome, thank you, Andrew.
link |
Thank you for joining me for my conversation
link |
with Dr. Samir Hattar.
link |
I hope you found it as interesting and informative as I did.
link |
If you're enjoying this podcast and or learning from it,
link |
please subscribe to our YouTube channel.
link |
In addition, please leave us comments and feedback
link |
in the comment section on YouTube.
link |
A great thing to do there would be to make suggestions
link |
about future topics you'd like us to cover
link |
or future guests you'd like me to host
link |
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In addition, please subscribe to our podcast
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And on Apple, you can leave us up to a five-star review.
link |
Please also check out the sponsors that we mentioned
link |
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link |
That's a terrific way to support us.
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And we have a Patreon, it's patreon.com slash Andrew Huberman
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and there you can support the podcast
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at any level that you like.
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For those of you that are interested
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in supporting scientific research,
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you can support the research in my laboratory on stress,
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on sleep and human performance and other related topics
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by going to Hubermanlab.stanford.edu slash giving
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and there you can make a tax deductible donation
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at any level that you like.
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If you're not already following us on Instagram,
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please follow us at Huberman Lab on Instagram
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and also on Twitter.
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Both those places I teach neuroscience
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and offer information that's not always covered
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on the Huberman Lab Podcast.
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And last, but certainly not least,
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thank you for your interest in science.
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I'll see you next time.