back to indexHow to Enhance Your Gut Microbiome for Brain & Overall Health | Huberman Lab Podcast #61
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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,
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and I'm a professor of neurobiology and ophthalmology
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at Stanford School of Medicine.
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Today, we are going to discuss the gut and the brain,
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and we are going to discuss
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how your gut influences your brain
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and your brain influences your gut.
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As many of you probably know,
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there is a phenomenon called your gut feeling,
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which tends to be something that you seem to know
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without really knowing how you know it.
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That's one version of the gut feeling.
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The other is that you sense something
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in your actual gut, in your body,
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and that that somehow drives you to think or feel or act
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in a particular way, maybe to move towards something
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or to move away from something.
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Now, today, we aren't going to focus so much
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on the psychology of gut feelings,
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but on the biology of gut feelings
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and how the gut and brain interact,
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because indeed your gut is communicating to your brain
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both directly by way of neurons, nerve cells,
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and indirectly by changing the chemistry of your body,
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which permeates up to your brain
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and impacts various aspects of brain function.
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But it works in the other direction too.
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Your brain is influencing your entire gut.
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And when I say entire gut, I don't just mean your stomach,
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I mean your entire digestive tract.
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Your brain is impacting things
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like how quickly your food is digesting,
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the chemistry of your gut.
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If you happen to be stressed or not stressed,
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whether or not you are under a particular social challenge
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or whether or not you're particularly happy
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will in fact adjust the chemistry of your gut
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and the chemistry of your gut in turn
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will change the way that your brain works.
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I'll put all that together for you
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in the context of what we call the gut microbiome.
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The gut microbiome are the trillions of little bacteria
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that live all the way along your digestive tract
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and that strongly impact the way that your entire body works
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at the level of metabolism, immune system,
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and brain function.
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And of course, we will discuss tools,
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things that you can do in order to maintain
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or improve your gut health.
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Because as you'll also soon see,
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gut health is immensely important
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for all aspects of our wellbeing,
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at the level of our brain, at the level of our body.
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And there are simple actionable things that we can all do
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in order to optimize our gut health
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in ways that optimize our overall nervous system functioning.
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So we will be sure to review those today.
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This episode also serves as a bit of a primer
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for our guest episode that's coming up next week
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with Dr. Justin Sonnenberg from Stanford University.
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Dr. Sonnenberg is a world expert in the gut microbiome
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and so we will dive really deep into the gut microbiome
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in all its complexity.
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We'll make it all very simple for you.
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We will also talk about actionable tools in that episode.
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This episode is a standalone episode,
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so you'll get a lot of information and tools,
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but if you have the opportunity to see this episode first,
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I think it will serve as a nice primer
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for the conversation with Dr. Sonnenberg.
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Before we begin, I'd like to emphasize
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that this podcast is separate
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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 Athletic Greens.
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Athletic Greens is an all-in-one
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vitamin mineral probiotic drink.
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I've been using Athletic Greens,
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which is now called AG1, since 2012,
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so I'm delighted that they're sponsoring the podcast.
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The reason I started taking Athletic Greens
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and the reason I still take Athletic Greens
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once or twice a day is that it covers
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all of my foundational vitamin and mineral needs
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and also because it contains high quality probiotics
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and prebiotics, which is a topic
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that we're going to talk a lot about today.
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With Athletic Greens, I can be sure
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so if I'm missing anything in my diet,
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I can compensate for that with the Athletic Greens.
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Plus, it has the probiotics and prebiotics
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that can also compensate for any deficiencies
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that I might have in creating the right environment
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for my gut microbiome.
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If you'd like to try Athletic Greens,
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you can go to athleticgreens.com slash Huberman
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to claim a special offer.
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They'll give you five free travel packs,
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which make it very easy to mix up Athletic Greens
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while you're in the car or on a plane
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While not everyone needs additional vitamin D3,
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and it also has K2 in there.
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K2 has been shown to be important for various aspects
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of calcium regulation, cardiovascular health, and so on.
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Again, go to athleticgreens.com slash Huberman
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to claim this special offer.
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Today's episode is also brought to us by Element.
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Element is an electrolyte drink that contains no sugar.
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It does, however, contain sodium, magnesium, and potassium.
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I've talked about sodium on the podcast before.
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I think sodium can indeed be problematic for some people
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with hypertension or pre-hypertension,
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but for many people, sodium is a great thing.
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It can increase blood volume
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in ways that can be helpful to them.
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It can improve nerve cell function
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in ways that can be helpful to them.
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I want to replace my electrolytes,
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You only pay the cost of shipping.
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Inside Tracker is a personalized nutrition platform
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and help you reach your health goals.
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for the simple reason that many of the things
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that impact your immediate and long-term health
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can only be assessed with a quality blood test.
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And nowadays, with the advent of modern DNA tests,
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you can also get insights into, for instance,
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what your biological age is
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and how that compares to your chronological age.
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Now, one of the major problems
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with a lot of blood tests and DNA tests out there
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They'll tell you if those numbers are in range
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Okay, let's talk about the gut and the brain
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and how your gut and your brain
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communicate in both directions.
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Because as I mentioned before,
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your gut is communicating all the time with your brain
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and your brain is communicating all the time with your gut.
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And so the two are in this ongoing dance with one another
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that ordinarily is below your conscious detection.
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Although you're probably familiar with the experience
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of every once in a while getting a stomach ache
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or of eating something that doesn't agree with you
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or conversely eating something
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that you find particularly delicious.
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And that sensation or that experience rather
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being a whole body experience.
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Your mind is excited about what you're eating or just ate.
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Your gut is excited about what you're eating or just ate.
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And it seems to be a kind of unified perception
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of both brain and body.
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Today, we're going to talk about how that comes about
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in the negative sense.
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Like, you know, when you meet someone you really dislike
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or when you have a stomach ache and in the positive sense,
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when you interact with somebody that you really, really like
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and you'd like to spend more time with them, for instance,
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or when you eat something that you really, really like
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and you'd like to spend more time with that food,
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Now, the gut and the brain represent
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what we call a biological circuit.
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Meaning they include different stations.
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So station A communicates with station B,
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which communicates with station C and so on.
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And as I mentioned earlier, it is bi-directional.
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It's a two way street between gut and brain.
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I want to make the important point at the outset
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that when I say the word gut, when I refer to the gut,
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I'm not just referring to the stomach.
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Most of us think that the gut equates to the stomach
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because we think of having a gut or not having a gut
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or having a gut feeling of some sort.
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But in the context of gut brain signaling
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and the related microbiome,
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the gut includes the entire digestive tract.
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That's right, from start to finish,
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the entire digestive tract.
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So much so that today we're going to talk about,
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for instance, the presence of neurons, nerve cells,
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that reside in your gut,
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that communicate to specific locations in the brain
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and cause the release of specific neurochemicals,
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such as the neurochemical dopamine or serotonin,
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that can motivate you to seek more of a particular food
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or type of interaction or behavior,
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or to avoid particular foods, interactions, and behaviors.
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And some of those neurons, many of those neurons, in fact,
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reside in your intestines, not in your stomach.
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They can be in the small intestine or the large intestine.
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In fact, you actually have taste receptors and neurons
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located all along your digestive tract.
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You have neurons that are located all along your digestive
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tract, and they are communicating to your brain
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to impact what you think, what you feel, and what you do.
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Okay, so for the gut brain axis,
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we need to deal with the brain part,
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and then we need to deal with the gut part.
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Let's just quickly talk about the brain part,
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because there, the word brain is also a bit of a misnomer,
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in that when we say the gut brain axis,
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it does include the brain,
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but includes a lot of other things as well.
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So as many of you probably know by now,
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if you're listeners of this podcast, and if you don't,
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Your nervous system includes your brain and your spinal
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cord, and those together constitute what's called
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the central nervous system.
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Your neural retinas, which are the lining the back
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of your eyes and are the light sensing portion of your eyes
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are also part of your central nervous system.
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So actually your eyes are part of your brain.
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They're the only parts of your brain that are outside
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the cranial vault.
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So your retinas, your brain proper,
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and your spinal cord make up the central nervous system.
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The other parts of your nervous system constitute what's
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called the peripheral nervous system,
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which are the components of your nervous system that reside
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outside the retinas, brain, and spinal cord.
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Now, this is very important because today we're going to
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talk a lot about how the gut communicates with the brain.
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And it does that by way of peripheral nervous system
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components, meaning nerve cells that reside in the gut
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and elsewhere in the body that communicate to the brain
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and cross into the central nervous system to influence
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what you think and what you feel.
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So that's the nervous system part of what we call
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the gut brain axis.
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Brain, again, just being a shorthand for including
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all the elements I just described.
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Gut, as you now know, includes all the elements
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of the digestive tract.
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Let's talk about the architecture or the structure
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of the gut of your digestive system.
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Not surprisingly, your digestive system,
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AKA your gut, begins at your mouth and ends at your anus.
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And all along its length, there are a series of sphincters
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that cut off certain chambers of the digestive tract
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from the other chambers.
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Now, also along this tube that we call the digestive tract,
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there's great variation in the degree of acidity or pH,
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as it's sometimes called.
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That variation in acidity turns out to give rise
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to different little micro environments
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in which particular microbiota, micro bacteria,
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can thrive or fail to thrive.
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And so the way I'd like you to think about
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the digestive tract, this gut component
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of the gut brain axis, is that it's not just one component.
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It's not just your stomach with a particular acidity
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and a bunch of microorganisms that work particularly well
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to make you feel good
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and make your digestive pathways work well.
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It's a series of chambers, little micro environments
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in which particular microbiota thrive
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and other microbiota do not.
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And certain behaviors that you undertake
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and certain experiences that you have
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will adjust those micro environments
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in ways that make particular microbiota, certain bacteria,
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more likely to thrive and others less likely to thrive.
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We'll talk about how that was set up for you
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Actually from the moment that you came into the world,
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that microbiome was being established.
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It was actually strongly impacted,
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depending on whether or not you were born by C-section
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or by vaginal birth.
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And it was strongly impacted by who handled you
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when you came into the world.
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Literally the hands that were on you,
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how much skin contact you had,
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whether or not you were a preemie baby or not,
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whether or not you had pets at home,
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whether or not you were allowed to play in the dirt,
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whether or not you were allowed to eat snails
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or whether or not you were kept
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in a very antiseptic environment.
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All of those experiences shaped
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these little micro environments
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and shaped what constitutes best or worst
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for those micro environments.
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So you have this long tube that we call the digestive tract
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and it's very, very long.
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In fact, if we were to splay it out,
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we were to take all the curves and turns
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out of the intestine, we would find that it is very long.
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It's approximately nine meters long.
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Now the structure of that digestive tract
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turns out to be very important
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in terms of gut brain signaling.
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Once again, it's a tube and the hollow of that tube
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is called the lumen, L-U-M-E-N.
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But the walls of the tube are not necessarily smooth,
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at least not for significant portions
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of the digestive tract.
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For much of the digestive tract,
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there are bumps and grooves that look very much
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like the folds in the brain,
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but these bumps and grooves are made up of other tissues.
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They're made up of what's called a mucosal lining.
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So there's a lot of mucus there.
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And if we were to look really closely,
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what we'd find is that there are little hairy
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like cellular processes that we call microvilli
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that are able to push things along the digestive tract.
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The microbiota reside everywhere along the lumen
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of the digestive tract, starting at the mouth
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and all the way to the other end.
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And they reside within those microvilli
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and they reside within the lumen.
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And if we were to look really closely
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at the bumps and grooves along the digestive tract,
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what we would find is that there are little niches,
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little areas in which particular things
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can grow and reside best.
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Now that might sound kind of gross,
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but it actually is a good thing,
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especially if what's growing and residing there
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are micro-bacterial organisms that are good for your gut
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and that signal good things to your brain.
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And we will talk about what that signaling looks like
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and how that's done and accomplished in just a few moments.
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But I want you to get a clear mental picture of your gut,
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something that we don't often see.
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And often when we think about the gut,
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again, we just think about the hollow of the stomach,
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food going in there and getting digested,
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but it's far more complex
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and actually far more interesting than that.
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Now I've been referring to the gut microbiome
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and to the microbiota and these bacteria.
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Let me define those terms a little bit more specifically
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just to avoid any confusion.
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The microbiota are the actual bacteria.
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The microbiome is used to refer to the bacteria,
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but also all the genes that those bacteria make,
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because it turns out that they make some important genes
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that actually impact all of us.
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You have loads and loads of these little microbiota,
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In fact, right now you are carrying with you
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about two to three kilograms.
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So that's more than six pounds of these microbiota,
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And if we were to look at them under a microscope,
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what we would see is these are relatively simple
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little organisms, some remain stationary.
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So they might plop down into the mucosal lining,
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or they might hang out on a particular microvilli,
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or they might be in one of those little niches
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and others can move about.
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But they basically fill the entire lumen,
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they surround and kind of coat the surface of the microvilli
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and they're tucked up into any of those little niches
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that are available to them to tuck into.
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If you were to take the head of a pin
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and look at it under the microscope,
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you could fit many, many hundreds, if not thousands or more
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of these little microbacteria.
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And the reason I say many, many thousands or more,
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I'm giving a kind of broad range there,
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is that they do vary in size.
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And again, they vary as to whether or not they can move
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or they don't move.
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Now they're constantly turning over in your gut,
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meaning they're being born, so to speak,
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and they're dying off.
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And some will stay there for very long periods of time
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within your gut and others will get excreted.
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About 60% of your stool,
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as unpleasant as that might be to think about,
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is made up of live and dead microbacteria.
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So you're constantly making
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and excreting these microbacteria.
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And which microbacteria you make
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and how many stay inside your gut and how many leave,
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meaning how many are excreted,
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depends a lot on the chemistry of your gut
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and depends very strongly on the foods that you eat
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and the foods that you do not eat.
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Now, just because what we eat strongly influences
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our microbiome, meaning our microbacteria,
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does not mean that there are not other influences
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on what constitutes our microbiome.
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Our microbiome is also made up by microbacteria
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that access our digestive tract through our mouth,
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through breathing, through kissing,
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and through skin contact.
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In fact, one of the major determinants of our microbiome
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is who we interact with
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and the environment that we happen to be in.
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And that actually includes
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whether or not we interact with animals.
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In a little bit, I'll talk about some data
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as to whether or not you grew up in a home that had animals,
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whether or not you grew up in the home,
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whether or not there was a lot of social contact,
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meaning skin contact,
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or whether or not you grew up
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in a more animal-sparse, contact-sparse environment
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and how that shapes your microbiome.
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But the simple point is
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that what you eat influences your microbiome,
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but also what you do, what you think, and what you feel,
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and many of the little microbacteria
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that get into your digestive tract
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do so by way of social interactions.
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In fact, if you ask a neurobiologist
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what the role of the microbiome is,
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they'll tell you almost certainly
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that it's there to impact brain function.
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But if you have friends that are microbiologists,
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such as I do, they'll tell you,
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well, maybe the brain and nervous system
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are there to support the microbiome.
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It's the other way around.
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You have all these little microorganisms
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that are taking residence in our body.
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They don't really know what they're doing as far as we know.
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We don't know that they have a consciousness or they don't.
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We can't rule that out, but it seems pretty unlikely.
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Nonetheless, they are taking advantage
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of the different environments all along your digestive tract.
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They are taking advantage
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of the sorts of social interactions.
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For instance, the people you talk to and that breathe on you
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the people that you shake hands with,
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the people that you kiss or don't kiss,
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the people that you happen
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to be romantically involved with or not,
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your dog, your cat, your lizard, your rat,
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whatever pet you happen to own is impacting your microbiome.
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There's absolutely no question about that.
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So hopefully now you have some sense
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of the architecture of the digestive pathway
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and you have some sense
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of the trillions of little microbacteria
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that are living all along the different components
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of that digestive pathway.
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But what we haven't talked about yet
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and what I'd like to talk about now
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is what those little microbiota are actually doing
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in your digestive tract.
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In addition to just living there
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for their own intents and purposes,
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they are contributing, for instance, to your digestion.
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Many of the genes that those microbiota make
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are genes that are involved in fermentation
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and genes that are involved in digestion
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of particular types of nutrients.
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And in a little bit, we will talk about
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how what you eat can actually change the enzymes
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that those microbiome components make.
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Enzymes largely being things
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that are responsible for digestion.
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They catalyze other sorts of cellular events,
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but in the context of the digestive pathway,
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we're talking about enzymes that help digest your food.
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So those microbiota are indeed helping you in many ways.
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And if you lack certain microbiota
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that can help you digest,
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it stands to reason that you would have challenges
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digesting certain types of foods.
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The other amazing thing that these microbiota do
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is they change the way that your brain functions
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by way of metabolizing or facilitating the metabolism
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of particular neurotransmitters.
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So one of the ways that having certain microbiota
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present in your gut can improve your mood
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or degrade your mood, for instance,
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is by way of certain microbiota being converted into
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or facilitating the conversion of chemicals such as GABA.
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GABA is what we call an inhibitory neurotransmitter.
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It's involved in suppressing the action of other neurons.
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And that might sound like a bad thing,
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but all types of sedatives, for instance,
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alcohol and a lot of neurons that naturally make GABA
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can help quiet certain circuits in the brain.
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For instance, circuits responsible for anxiety.
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In people who have epilepsy,
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the GABAergic neurons, as they're called,
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can often be disrupted in their signaling,
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meaning they're not cranking out as much GABA,
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and therefore the excitatory neurons,
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which typically release other molecules like glutamate,
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can engage in what's called runaway excitation,
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and that can give rise to seizures.
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So the simple message here is that the microbiota,
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by way of making neurochemicals,
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can influence the way that your brain functions.
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So you want to support those microbiota,
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and we will give you tools to support those microbiota.
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But the takeaway at this point is that those microbiota
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are making things locally to help digest food.
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Other microbiota are helping
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to make certain neurotransmitters like GABA,
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and we'll also talk about dopamine and serotonin.
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And so the very specific microbiota that reside in your gut
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have a profound influence on many, many biological functions,
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especially immune system function,
link |
brain function, and digestion.
link |
So that should give you a fairly complete picture
link |
of your gut microbiome.
link |
Now I'd like to talk about how your microbiome
link |
and your brain communicate,
link |
or more accurately, how your microbiome
link |
and the rest of your nervous system communicate.
link |
Neurons, which simply means nerve cells,
link |
are the cells that do most of the heavy lifting
link |
in your nervous system.
link |
There are, of course, other cell types
link |
that are important, glial cells, for instance,
link |
very, very important cell types.
link |
You have endothelial cells,
link |
which are responsible for blood flow, pericytes,
link |
and other types of cells.
link |
But the neurons are really doing most of the heavy lifting
link |
for most of the things we think about
link |
in terms of nervous system function.
link |
You have neurons in your gut,
link |
and that should not surprise you.
link |
Neurons reside in your brain, your spinal cord, your eyes,
link |
in fact, all over your body,
link |
and you've got them in your heart,
link |
and you've got them in your lungs,
link |
and you've got them in your spleen,
link |
and they connect to all the different organs
link |
and tissues of your body.
link |
So that's not surprising that you have neurons in your gut.
link |
What is surprising, however,
link |
is the presence of particular types of neurons
link |
that reside near or in the mucosal lining
link |
just next to that lumen of the gut,
link |
and that are paying attention,
link |
and I'll explain what I mean by paying attention,
link |
to the components of the gut,
link |
both the nutrients and the microbiota,
link |
and thereby can send signals up to the brain
link |
by way of a long wire that we call an axon,
link |
and can communicate what the chemistry
link |
and what the nutritional quality
link |
and what the other aspects of the environment
link |
are at the gut at a given location up to the brain
link |
in ways that can influence the brain to, for instance,
link |
seek out more of a particular food.
link |
Let me give you a sort of action-based picture of this.
link |
Let's say, like most people, you enjoy sweet foods.
link |
I don't particularly enjoy sweet foods,
link |
but there are a few that I like.
link |
I'm a sucker for a really good dark chocolate,
link |
or really good ice cream,
link |
or I got this thing for donuts that seems to just not quit,
link |
although I don't tend to indulge it very often.
link |
If I eat that particular food,
link |
obviously digestion starts in the mouth,
link |
there are enzymes there, it gets chewed up,
link |
the food goes down into the gut.
link |
These neurons are activated,
link |
meaning that causes the neurons to be electrically active
link |
when particular components,
link |
certain nutrients in those foods are present.
link |
And for the cell types,
link |
or I should say the neuron types that matter here,
link |
the nutrients that really trigger their activation
link |
are sugar, fatty acids, and amino acids.
link |
Now, these particular neurons
link |
have the name enteroendocrine cells,
link |
but more recently they've been defined as neuropod cells.
link |
Neuropod cells were discovered by Diego Bohorquez's lab
link |
at Duke University.
link |
This is a phenomenal set of discoveries
link |
made mostly in the last 10 years.
link |
These neuropod cells, as I mentioned,
link |
are activated by sugar, fatty acids, or amino acids,
link |
but have a particularly strong activation to sugars.
link |
They do seem to be part of the sweet sensing system.
link |
And even though I'm focusing on this particular example,
link |
they represent a really nice example
link |
of how a particular set of nerve cells in our gut
link |
is collecting information about what is there
link |
at a particular location in the gut
link |
and sending that information up to our brain.
link |
Now, they do that by way of a nerve pathway
link |
called the vagus nerve.
link |
The vagus nerve is part of the peripheral nervous system,
link |
and the vagus nerve is a little bit complex to describe
link |
if you're just listening to this.
link |
If you're watching this,
link |
I'll try and use my hands as a diagram,
link |
but really the best thing to do
link |
if you really want to learn neuroanatomy
link |
is to just imagine it in your mind as best you can,
link |
and if you can track down a picture of it, terrific.
link |
But here's how it works.
link |
Neurons have a cell body that we call a soma.
link |
That's where all the DNA are contained.
link |
That's where a lot of the operating machinery
link |
of the cells are contained,
link |
and a lot of the instructions for that cell
link |
of what to be and how to operate are contained.
link |
The cell bodies of these neurons, or the relevant neurons,
link |
are actually up near the neck.
link |
So you can think of them as kind of a clump of grapes
link |
because cell bodies tend to be round or oval-ish.
link |
And then they send a process that we call an axon
link |
in one direction out to the gut,
link |
and they'll send another process up into the brain.
link |
And that little cluster near the neck that's relevant here
link |
is called the nodose ganglion, N-O-D-O-S-E.
link |
The nodose ganglion is a little cluster of neurons
link |
on either side of the neck.
link |
It has a process that goes out to the gut
link |
and a process that goes up into the brain.
link |
And again, these are just one component
link |
of the so-called vagus nerve.
link |
The vagus nerve has many, many branches,
link |
not just to the gut.
link |
There are also branches to the liver,
link |
branches to the lungs, branches to the heart,
link |
branches to the larynx, and even to the spleen
link |
and other areas of the body that are important.
link |
But right now, we're just concentrating on the neurons
link |
that are in the gut that signal up to the brain.
link |
And what the Bohorkas lab has shown
link |
is that these neuropod cells are part of this network.
link |
They're sensing several different nutrients,
link |
but in particular, when they send sugar,
link |
they send signals in the form of electrical firing
link |
up to the brain in ways that trigger activation
link |
of other brain stations that cause you to seek out
link |
more of that particular food.
link |
Now, this brings us to some classic experiments
link |
that, at least to me, are incredible.
link |
And these are highly reproducible findings
link |
showing, for instance, that even if you bypass taste
link |
by infusing sweet liquid or putting sweet foods into the gut
link |
and people can never taste them with their mouth,
link |
people will seek out more of that particular food.
link |
And if you give them the option to have a sweet food
link |
infused into their gut or a bitter food
link |
infused into their gut or a sweet versus sour
link |
or a more sweet versus less sweet food,
link |
people have a selective preference for sweet foods
link |
even if they can't taste them.
link |
Now, this is important to understand
link |
in the context of gut brain signaling,
link |
because we always think that we like sweet foods
link |
because of the way they taste.
link |
And indeed, that's still true,
link |
but much of what we consider the great taste of a sweet food
link |
also has to do with a gut sensation
link |
that is below our conscious detection.
link |
How do we know that?
link |
Well, the Bohorkas lab has performed experiments
link |
using modern methods and their classic experiments
link |
showing that animals and humans will actively seek out
link |
more of a particular sweet food
link |
even if it bypasses this taste system.
link |
And the reverse is also true.
link |
There have been experiments done in animals and in humans
link |
that have allowed animals or humans
link |
to select and eat sweet foods.
link |
And indeed, that's what they do if they're given the option.
link |
And yet to somehow eliminate the activation of these neurons
link |
within the gut that can sense sweet foods.
link |
Now, there are a couple of different ways
link |
that those experiments have been done.
link |
In classic experiments that date back to the 80s,
link |
this was done by what's called subdiaphragmatic vagotomy.
link |
So this means cutting off the branch of the vagus
link |
that innervates the gut below the diaphragm
link |
so that the other organs can still function
link |
because the vagus is very important.
link |
But basically cutting off the sweet sensing in the gut,
link |
still giving people the opportunity
link |
to taste sweet foods with their mouth,
link |
and they don't actively seek out
link |
quite as much of the sweet food
link |
when they don't have this gut sensing mechanism
link |
that we now know to be dependent on these neuropod cells.
link |
More recent experiments involve selective silencing
link |
of these neuropod cells,
link |
and there've been a lot of different derivations
link |
of this sort of thing.
link |
But the takeaway from it is that our experience of
link |
and our desire for particular foods
link |
has everything to do with how those foods taste.
link |
It also has to do, as you probably know, with their texture
link |
and the sensation of those foods in our mouth,
link |
and even indeed how they go down our throat
link |
sometimes can be very pleasing or very unpleasant.
link |
And it also has to do with the subconscious processing
link |
of taste that occurs in the gut itself.
link |
And again, when I say gut, I don't just mean in the stomach.
link |
There are actually neurons, neuropod cells
link |
further down your digestive tract,
link |
which are signaling to your brain
link |
about the presence of sweet foods,
link |
as well as foods such as amino acid rich foods
link |
or foods that are rich in particular types of fatty acids
link |
signaling up to your brain and causing you to seek out
link |
more of those foods or to consume more of those foods.
link |
Now you're probably asking, what is the signal?
link |
How does it actually make me want more of those foods
link |
without me realizing it?
link |
Well, it does that by adjusting the release
link |
of particular neuromodulators.
link |
For those of you that are not familiar with neuromodulators,
link |
these are similar to neurotransmitters,
link |
but they tend to act more broadly.
link |
They tend to impact many more neurons all at once.
link |
And they go by names like dopamine, serotonin,
link |
acetylcholine, epinephrine, and so forth.
link |
Sometimes people refer to those as neurotransmitters.
link |
Technically they are neuromodulators.
link |
I'll refer to them almost always as neuromodulators.
link |
The neuropod cells signal by way of a particular branch
link |
of the vagus through the nodose ganglion
link |
that we talked about before,
link |
and through a number of different stations
link |
in the brainstem eventually cause the release
link |
of the neuromodulator dopamine.
link |
Dopamine is often associated with a sense of pleasure
link |
and reward, but it is more appropriately thought of
link |
as a neuromodulator that impacts motivation,
link |
craving, and pursuit.
link |
It tends to put us into modes of action,
link |
not necessarily running and moving through space,
link |
although it can do that too.
link |
But in the context of feeding,
link |
it tends to make us look around more, chew more,
link |
reach for things more, and seek out more of whatever it is
link |
that's giving us that sensation of delight or satisfaction.
link |
And again, that sense of delight and satisfaction
link |
you might experience only consciously
link |
as the way that something tastes on your mouth,
link |
but it actually is caused again
link |
by both the sensations in your mouth,
link |
but also by the activation of these neuropod cells.
link |
So this is an incredible system of gut brain signaling,
link |
and it is but one system of gut brain signaling.
link |
It turns out it's the system that we know the most about
link |
at this point in time.
link |
There are other components of gut brain signaling
link |
that we'll talk about in a moment.
link |
For instance, the serotonin system.
link |
But in terms of examples of gut brain signaling
link |
for which we know a lot of the individual elements
link |
and how they work, I think this neuropod neuron sensing
link |
of sweet foods, fatty acids, and amino acids in the gut,
link |
and communicating that up to the brain by way of the vagus
link |
and causing us to seek out more of the foods
link |
that deliver those nutrients is an incredible pathway
link |
that really delineates the beauty
link |
and the power of this gut brain axis.
link |
Let me talk about timescales.
link |
Here I'm talking about a particular type of neuron
link |
that is signaling up to the brain using electrical signals
link |
to cause us to want to seek out
link |
a particular category of foods.
link |
That's happening relatively fast
link |
compared to the hormone pathways of the gut,
link |
which also involve neurons.
link |
So your gut is also communicating to your brain
link |
by way of neurons, nerve cells.
link |
But some of those nerve cells also release hormones.
link |
And those hormones go by names like CCK,
link |
glucagon-like peptide one, PYY, et cetera.
link |
A good example of a hormone pathway
link |
or what sometimes is called a hormone peptide pathway
link |
that is similar to the pathway I've talked about before,
link |
but a little bit slower is the ghrelin pathway.
link |
Ghrelin, G-H-R-E-L-I-N,
link |
increases with fasting.
link |
So the longer it's been since you've eaten
link |
or if you're just eating very little food
link |
compared to your caloric needs,
link |
ghrelin levels are going to go up in your bloodstream
link |
and they go up because of processes
link |
that include processes within the gut
link |
and include the nervous system.
link |
So it's a slow pathway driving you
link |
to seek out food generally.
link |
As far as we know, the ghrelin system is not partial
link |
to seeking out of sweet foods or fatty foods or so on.
link |
Ghrelin increases the longer it's been
link |
since you've eaten sufficient calories
link |
and it stimulates a feeling of you wanting to seek out food.
link |
Well, how does it do that?
link |
It does that again by impacting neural circuits
link |
within the brain, neural circuits that include
link |
what we call the brainstem autonomic centers.
link |
So it tends to make you feel alert
link |
and quite, we say high levels of autonomic arousal.
link |
If you haven't eaten in a while,
link |
you might think that you just get really exhausted, right?
link |
Because we all hear that food is energy
link |
and caloric energy is what we need to burn,
link |
but you actually have a lot of energy stored in your body
link |
that you would be able to use if you really needed energy.
link |
But typically we haven't eaten in a while,
link |
we start to get agitated
link |
and we get agitated by way of release
link |
of the neuromodulator epinephrine,
link |
which causes us to look around more,
link |
move around more and seek out food.
link |
That all occurs in brainstem autonomic centers
link |
and in the hypothalamus.
link |
We did an entire episode on feeding behavior
link |
and metabolism as well,
link |
and you can find those episodes at hubermanlab.com.
link |
So I don't want to go into a lot of detail
link |
about hypothalamic and brainstem centers,
link |
but there's a particular area of the brain
link |
called the nucleus of the solitary tract,
link |
the NST as it's called,
link |
that's very strongly impacted by these circulating hormones
link |
and tends to drive us toward feeding behavior.
link |
So the important point here is that we have a fast system
link |
that is paying attention to the nutrients in our gut
link |
or the absence of nutrients in our gut
link |
and stimulating us to seek out food
link |
or to stop eating certain foods.
link |
And we have a slower hormone-related system
link |
that also originates in the gut and impacts the brain.
link |
But all of those converge on neural circuits for feeding.
link |
The neural circuits for feeding include things
link |
like the arcuate nucleus, the hypothalamus,
link |
they include a bunch of other neurochemicals,
link |
but the point is that you've got a fast route
link |
and a slow route to drive you to eat more or eat less,
link |
to seek out food and consume it, or to stop eating,
link |
to essentially kickstart the satiety mechanisms
link |
as they're called.
link |
And those are operating in parallel.
link |
It's not like one happens first, then stops, then the other.
link |
They're always operating in parallel.
link |
And I bring this up because there's a bigger theme here,
link |
which we see over and over again in biology,
link |
which is the concept of parallel pathways.
link |
You've always got multiple accelerators
link |
and multiple breaks on a system.
link |
It's very, very rare to have just one accelerator
link |
and one break on the system.
link |
And this will become important later
link |
when we talk about tools for optimizing your gut microbiome
link |
for healthy eating and for healthy digestion
link |
and for healthy brain function.
link |
I want to take a moment
link |
and talk about glucagon-like peptide 1,
link |
which is also called GLP-1.
link |
GLP-1 is made by neurons in the gut
link |
and by neurons in the brain.
link |
This is a fairly recent discovery, but it's an important one.
link |
GLP-1 tends to inhibit feeding
link |
and tends to reduce appetite.
link |
There are a number of drugs released on the market now.
link |
One, for instance, goes by the name semaglutide,
link |
which is essentially an GLP-1 agonist.
link |
It causes the release of more GLP-1.
link |
It's being used to treat type 2 diabetes,
link |
which is insulin resistant diabetes.
link |
This is different than type 1 diabetes,
link |
where people don't actually make insulin.
link |
It's also being used as a drug to reduce obesity.
link |
And it seems pretty effective,
link |
at least in certain populations.
link |
There are certain foods and substances that increase GLP-1.
link |
I've talked about a few of these on the podcast.
link |
One that I'm a particular fan of
link |
for entirely other reasons is yerba mate tea
link |
can stimulate the release of GLP-1.
link |
In South America, it's often used as an appetite suppressant,
link |
probably in large part
link |
because of its effects on GLP-1 release,
link |
but probably also because it does contain caffeine,
link |
which is a bit of a stimulant,
link |
which also can be involved in lipolysis,
link |
which is the utilization of fat stores for energy
link |
A brief mention about yerba mate.
link |
There are some reports out there
link |
that yerba mate can increase certain types of cancers.
link |
The data that I've seen on this
link |
is that it tends to relate to whether or not
link |
those are smoked versions of the yerba mate tea,
link |
the amount of consumption, and the debate is still out.
link |
So I invite you to look at those papers.
link |
You can search for those online.
link |
Nonetheless, yerba mate is one source of GLP-1 stimulation.
link |
Semaglutide is another source.
link |
It also can be stimulated by various foods,
link |
nuts, avocados, eggs, and so forth.
link |
Certain high fiber complex grains will also stimulate GLP-1.
link |
I raise this as not necessarily a route
link |
that you want to take in order to reduce food intake.
link |
I don't even know that that's your goal,
link |
but that GLP-1 is another one of these gut
link |
to brain signaling mechanisms that adjusts appetite
link |
that is dependent on diet,
link |
depends on what you eat or drink,
link |
and that the GLP-1 pathway does seem particularly sensitive
link |
to the constituents of diet.
link |
There's at least one quality study I was able to find
link |
showing that the ketogenic diet, for instance,
link |
which almost always involves ingestion
link |
of very low levels of carbohydrate, can increase GLP-1.
link |
Although, as I mentioned before,
link |
there are other foods that fall outside the range
link |
of what we would consider ketogenic
link |
that can also stimulate GLP-1.
link |
And as I mentioned, there are prescription drugs
link |
like semaglutide, there are other ones as well now,
link |
that stimulate GLP-1.
link |
So how does GLP-1 reduce appetite?
link |
It does that in part by changing the activity of neurons
link |
in the hypothalamus, this cluster of neurons
link |
just above the roof of our mouth
link |
that themselves make GLP-1
link |
and that cause the activation of motor circuits
link |
for reaching, chewing, all the things that we associate
link |
with feeding behavior.
link |
So I use GLP-1 as an example of a pathway
link |
that you might choose to tap into by ingestion
link |
of Yerba Monte or by ingestion of the foods I mentioned,
link |
or if it's something that interests you, ketogenic diet.
link |
But I also mention it simply
link |
because it's another beautiful example
link |
of how a hormone pathway can impact the activity
link |
of brain circuits that are directly involved
link |
in a particular behavior.
link |
So yet another example of how gut is communicating
link |
to brain in order to change what we think we want
link |
or to change what our actual behaviors are.
link |
So the next time you find yourself reaching for food
link |
or you find yourself wanting a particular sweet thing
link |
or fatty thing or something that contains a lot
link |
of amino acids, a protein rich food,
link |
keep in mind that that's not just about the taste
link |
And it's not even necessarily about the nutrients
link |
that you need or don't need, it could be,
link |
but it's also about the subconscious signaling
link |
that's coming from your body all the time,
link |
waves of hormones, waves of nerve cell signals,
link |
electrical signals that are changing the way
link |
that your brain works.
link |
And this raises for me a memory of the episode
link |
that I did with Dr. Robert Sapolsky,
link |
who's a world expert colleague of mine at Stanford,
link |
who is expert on things like hormones and behavior.
link |
But we got into the topic of free will,
link |
which is a bit of a barbed wire topic.
link |
As many of you know, it gets into the realm
link |
of philosophy, et cetera, and we were kind of batting back
link |
and forth the idea, I was saying, well,
link |
I think there's free will and can't there certainly
link |
be free will or certainly the idea
link |
that we can avoid certain choices.
link |
And Robert was saying, no, in fact, he said, nah,
link |
he doesn't believe that we have any free will.
link |
He thinks that events in our brain are determined
link |
by biological events that are below our conscious detection
link |
and that occur seconds to milliseconds
link |
before we make decisions or assessments.
link |
And therefore we just can't control what we do,
link |
what we think and what we feel.
link |
And at the time I sort of didn't buy it.
link |
I thought, I don't know.
link |
I just, I guess I really wanted to believe in free will.
link |
And to some extent I still do.
link |
But as we talk about how these neurons in our gut
link |
and these hormones in our gut are influencing our brain
link |
and the decisions that we are making,
link |
at the level of circuits like the hypothalamus
link |
and the nucleus of the solitary tract,
link |
these are areas of the brain way below our frontal cortex
link |
and our conscious perception.
link |
I think these are examples that really fall in favor
link |
of what Dr. Sapolsky was arguing,
link |
which is that events that are happening within our body
link |
are actually changing the way our brain works.
link |
So we might think that we want the cupcake.
link |
We might think that we don't need to eat something
link |
or do need to eat something.
link |
And that is entirely on the basis of prior knowledge
link |
and decision-making that we're making with our head.
link |
But in fact, it's very clear to me
link |
based on the work from the Bohork's lab,
link |
classic work over the years,
link |
dating back to the 80s and indeed back to the 50s
link |
that we'll talk about in a moment,
link |
that our body is shaping the decisions
link |
that our brain is making and we're not aware of it at all.
link |
Now, the good news is that whether or not
link |
you believe in free will or not,
link |
the simple knowledge that this whole process is happening
link |
can perhaps be a benefit to you.
link |
You can perhaps leverage it to get some insight
link |
and understanding and perhaps even a wedge
link |
into your own behavior.
link |
You might think, ah, I think I want that particular food
link |
or I think I want to avoid that particular food,
link |
but actually that's not a decision
link |
that I'm making on a purely rational basis.
link |
It has a lot to do with what my gut is telling my brain.
link |
So we've largely been talking about chemical communication
link |
between the gut and the brain.
link |
Chemical because even though these neuropod cells
link |
are communicating with the brain
link |
by way of electrical activity,
link |
what we call action potentials,
link |
and in neural language, we call those spikes,
link |
spikes of action potentials.
link |
Spikes of action potentials, meaning those neural signals,
link |
cause the release of chemicals in the brain like dopamine.
link |
So it's chemical transmission.
link |
Similarly, hormones, even though they act more slowly,
link |
hormones like neuropeptide Y, like CCK, like ghrelin,
link |
they are signaling chemically.
link |
They're moving through the body.
link |
They're going in there affecting the chemical output
link |
of different cells,
link |
and they're changing the chemistry of those cells
link |
and the chemistry of the cells that those cells talk to.
link |
So that gives us one particular category of signaling
link |
from gut to brain, which is chemical signaling.
link |
But of course, there are other forms of signals,
link |
and those fall under the category of mechanical signaling.
link |
You're probably familiar with this.
link |
If you've ever eaten a very large meal
link |
or consumed a lot of fluid,
link |
you experience that as distension of the gut,
link |
and that doesn't just have to be distension of the stomach,
link |
but distension of your intestines as well.
link |
That distension is registered by neurons
link |
that reside in your gut.
link |
The signals go up to your brain
link |
and communicate with areas of the brain
link |
that are responsible for suppressing further consumption
link |
of food and or fluid,
link |
and under certain circumstances can also be associated
link |
with the activation of neural circuits
link |
that cause vomiting or the desire to vomit.
link |
So if ever you've eaten too much
link |
or you've eaten something that doesn't agree with you,
link |
that information is communicated by way of mechanosensors
link |
that sense the mechanics of your gut,
link |
possibly also the chemistry of your gut,
link |
but mostly the mechanics of your gut,
link |
signal up to the brain and activate brain centers
link |
that are involved in stopping the eating behavior
link |
and activation of an area of the brainstem
link |
that is affectionately referred to as the vomit center
link |
among neuroanatomists.
link |
This is a area that more appropriately
link |
is called the chemoreceptor trigger zone,
link |
the CTZ or area postrema and neurons in this area
link |
actually will trigger the vomiting reflex.
link |
So the way that the gut and the brain communicate
link |
is both chemical and mechanical,
link |
and it can be both for sake
link |
of increasing certain types of behavior.
link |
Today we're talking mainly about feeding behavior
link |
up until now anyway, but also ceasing to eat,
link |
closing your mouth, moving away from food,
link |
turning away from food,
link |
all behaviors that we're familiar with
link |
anytime we feel kind of sick on the basis of activation
link |
of this mechanosensor for gastric distress.
link |
So we've got chemical signaling and mechanical signaling.
link |
And I also want to emphasize that we have direct
link |
and indirect signaling from the gut to the brain.
link |
Direct signaling is the kind of signaling
link |
of the sort I've been talking about mainly up until now,
link |
which is neurons in the gut,
link |
communicating with neurons in the brainstem
link |
that communicate with neurons in the hypothalamus.
link |
And of course, those are also going to interact
link |
with neurons of the prefrontal cortex,
link |
which is the area of your brain involved
link |
in decision-making, the, you know,
link |
I think it was the shrimp that made me sick.
link |
I'm going to, I just don't want any more of that.
link |
Or I'm never going back to that restaurant again,
link |
because after I ate there about an hour later,
link |
I started feeling really not well.
link |
I felt kind of feverish, but my gut didn't feel well.
link |
My digestion was really off.
link |
All of that kind of information is handled
link |
in the prefrontal cortex at a conscious level,
link |
but the immediate decision to stop eating
link |
or to eat more of something,
link |
to move towards something or away from it,
link |
that's made by neural circuits that reside at the,
link |
we would say the subconscious level.
link |
But what we really mean is below the level of the neocortex.
link |
Below the cortex means essentially
link |
below our level of conscious awareness.
link |
So we talked about two types of information within the gut
link |
that are communicated to the brain.
link |
Chemical information, meaning information
link |
about the nutrients that happen to be there
link |
and mechanical information,
link |
distension of the gut or lack of distension and so forth.
link |
And we talked about how these neuropod cells
link |
can signal the release of dopamine
link |
in circuits within the brain
link |
to cause you to seek out more of something.
link |
Now, in a very logically consistent way,
link |
dopamine is also involved in the whole business of vomiting.
link |
You might think, well, that doesn't make any sense.
link |
I thought dopamine was always a good thing.
link |
It's involved in moderation and reward, et cetera.
link |
But turns out the area postrema,
link |
this vomit center and the brainstem
link |
is chock-a-block full of dopamine receptors.
link |
And if dopamine levels go too high,
link |
it can actually trigger vomiting.
link |
And this we see in the context of various drugs
link |
that are used to treat things like Parkinson's.
link |
Parkinson's is a deficiency in dopamine
link |
or a lack of dopamine neurons,
link |
typically that causes a resting tremor,
link |
difficulty in movement,
link |
because dopamine is also associated
link |
with a lot of the neural circuits for movement.
link |
Many drugs that are used to treat Parkinson's like L-DOPA
link |
increase levels of dopamine so much,
link |
or at least activate dopamine receptors
link |
to such a great degree in certain areas of the brain
link |
that they can cause activation of things
link |
like the trigger to vomit.
link |
Now, this should also make sense in the natural context
link |
of if you gorge yourself with food,
link |
gorge yourself with food, gorge yourself with food,
link |
the neurons in your gut that respond to that
link |
are simply detecting the presence of nutrients,
link |
but they don't really make decisions themselves.
link |
They don't know to stop eating.
link |
Your brain knows to stop eating or to eject that food.
link |
And so it's a wonderful thing that those neurons
link |
are communicating with areas of the brain,
link |
not just that stimulate consuming more food,
link |
but that are communicating with areas of the brain,
link |
for instance, areopostrema,
link |
that when dopamine levels get too high,
link |
cause us to either stop eating that food
link |
or in the case of vomiting, to eject that food.
link |
and not to give you a kind of a disgusting counterexample
link |
to what we call repetitive behaviors,
link |
things that we like to do more of,
link |
but simply to give you a sense of just how strongly
link |
even these reflexes that we think of
link |
as feeling sick and vomiting,
link |
or the desire to seek out more food
link |
are really being controlled by a kind of push-pull system,
link |
by parallel pathways that are arriving from our gut.
link |
And the same neurochemicals, in this case, dopamine,
link |
are being used to create two opposite type behaviors,
link |
one behavior to consume more,
link |
one behavior to get rid of everything
link |
you've already consumed.
link |
So our brain is actually sensitive
link |
to the amount of signaling coming from our gut,
link |
not just the path by which that signal arrives.
link |
Our brain is very carefully paying attention
link |
to whether or not the levels of dopamine
link |
that are being triggered are within a normal range
link |
for typical eating behavior,
link |
or whether or not we've gorged ourselves
link |
to the point where enough already.
link |
Now, of course, mechanical signals will also play
link |
into areopostrema and into the vomiting reflex.
link |
If we have a very distended gut, we feel lousy,
link |
it just, it actually can hurt very badly,
link |
and we will have the desire to vomit,
link |
or we will just simply vomit.
link |
Mechanical and chemical signals
link |
are always arriving in parallel.
link |
They never work in unison.
link |
And so now we have chemical signals, mechanical signals,
link |
and now I'd like to talk about direct and indirect signals,
link |
because almost everything I've talked about up until now
link |
are direct signals, a neural pathway
link |
that converges in the brain
link |
to create a particular feeling, thought, or behavior,
link |
but there are also indirect pathways.
link |
And that's what takes us back to the gut microbiome
link |
and to these little microbiota.
link |
And to just give you the takeaway message at the front here,
link |
and then I'll give you a little more detail
link |
as to how it comes about.
link |
You have neurotransmitters in your brain
link |
and in your spinal cord and in your eyes
link |
and in your peripheral nervous system.
link |
They cause the activation or the suppression
link |
of nerve activity,
link |
meaning they either electrically activate other nerve cells
link |
or they cause other nerve cells to be less electrically
link |
active, and they do that by way of neurotransmitters.
link |
But as it turns out, the gut microbiota
link |
are capable of influencing metabolic events
link |
and in some cases are capable
link |
of synthesizing neurotransmitters themselves.
link |
So what that means is that these little bugs,
link |
these little microbiota that are cargo in your gut,
link |
the six pounds of cargo,
link |
they actually can make neurochemicals
link |
that can pass into the bloodstream and into your brain
link |
and actually impact the other cells
link |
of your body and brain indirectly.
link |
So without involving these very intricate nerve pathways
link |
that we've been talking about.
link |
In other words, the foods you eat,
link |
the environment of your gut microbiome
link |
can actually create the chemical substrates
link |
that allow your brain to feel one way or the other,
link |
to feel great or to feel lousy,
link |
to seek out more of a particular type of behavior
link |
or to avoid that behavior.
link |
And that would constitute indirect signaling.
link |
So I've been talking a lot about the structure
link |
and function of the gut to brain pathway,
link |
focusing mainly on feeding behaviors
link |
and in some cases, avoiding feeding
link |
or even ejecting food from the digestive tract.
link |
I'd like to drill a little bit deeper
link |
into this indirect signaling pathway
link |
from the gut to the brain,
link |
because it bridges us nicely from neuronal signals
link |
in the gut to the brain,
link |
hormonal signals from the gut to the brain,
link |
to what also includes the microbiome,
link |
which is what we started talking about
link |
at the beginning of the episode.
link |
As I mentioned a couple of minutes ago,
link |
certain gut microbiota can actually synthesize
link |
certain neurotransmitters that can go impact the brain.
link |
And we actually have some knowledge about which microbiota
link |
can synthesize particular neurotransmitters.
link |
For instance, the neuromodulator dopamine
link |
can be synthesized by or from bacillus and serratia.
link |
Now, these are just names of microbiota.
link |
I don't expect that any of you
link |
would necessarily recognize them.
link |
These aren't the sorts of things
link |
that you necessarily would have run out and buy
link |
to get more dopamine.
link |
But the point is that particular gut microbiota
link |
can create dopamine in our gut
link |
that can get into our bloodstream
link |
and can generally change our baseline levels of dopamine
link |
within the brain and other areas of the body.
link |
I mentioned baseline levels of dopamine
link |
because as I talked about on an episode all about dopamine,
link |
but I'll just repeat the basics here now,
link |
we have baseline levels of neurotransmitters
link |
or neuromodulators that act as sort of the level of the tide
link |
the overall level, and then we can have peaks of dopamine
link |
that are created by behaviors or by ingestion
link |
of particular foods or drugs, et cetera.
link |
So bacillus and serratia tend to increase
link |
our baseline levels of dopamine.
link |
So if it turns out that we are creating
link |
the right gut microbiome environment
link |
that these particular gut microbiota can thrive in,
link |
well then our baseline levels of dopamine will be elevated.
link |
And in general, that leads to enhancement of mood.
link |
Similarly, there are other gut microbiota,
link |
for instance, candida, streptococcus, various enterococcus.
link |
These always have these kind of strange
link |
and not so attractive names,
link |
at least to me as a neurobiologist.
link |
Nonetheless, those particular microbiota
link |
support the production of,
link |
or can even be metabolized into serotonin,
link |
which is a neuromodulator associated with mood,
link |
with social interactions, with a huge number
link |
of different types of events and behaviors.
link |
Again, these gut microbiota when present
link |
and allowed to thrive in our gut
link |
will increase our overall levels of serotonin
link |
and riding on top of that level of serotonin
link |
will be the serotonin that's specifically released
link |
in response to certain behaviors.
link |
And I really want to drive home this point
link |
of baselines and peaks.
link |
The baseline level of serotonin might set our overall mood,
link |
whether or not we wake up feeling pretty good
link |
or really lousy if our serotonin levels
link |
happen to be very, very low.
link |
Whether or not we tend to be in a kind of a calm space
link |
or whether or not we tend to be somewhat irritable.
link |
But then of course, individual events,
link |
as we go about our day, maybe a compliment that we get
link |
or maybe somebody says something irritating to us,
link |
whatever it may be, will also influence levels of serotonin.
link |
But those serotonin events are going to be related
link |
to events at particular neural circuits in the brain.
link |
And this is an important topic
link |
because I think that a lot of people hear quite accurately,
link |
oh, 90 to 95% of our serotonin is manufactured in the gut.
link |
And indeed that's true.
link |
It's manufactured from the sorts of microbiota
link |
that I just described.
link |
And there are many, many experiments now,
link |
mostly in animal models, but also some in humans
link |
that show that if the gut microbiome is deficient
link |
in some way to these particular bacteria,
link |
that serotonin levels drop and people's mood suffers,
link |
maybe even their immune system functions,
link |
maybe even exacerbates certain psychiatric illnesses.
link |
However, a lot of people take that to mean
link |
that the serotonin of the brain all comes from the gut
link |
or mostly comes from the gut.
link |
That's not the case.
link |
It's still the case that you have neurons in the brain
link |
that are responsible for releasing their serotonin directly
link |
in response to certain things like social touch
link |
or through other types of positive social experiences.
link |
So we've got gut microbiota
link |
that can literally be turned into dopamine
link |
and raise our baseline levels of dopamine.
link |
We've got gut microbiota
link |
that can literally raise our baseline levels of serotonin.
link |
And indeed there are other gut microbiota
link |
like lactobacillus or bifidobacterium,
link |
hard complex names to pronounce, bifidobacterium
link |
that can give rise to increases in GABA levels,
link |
this inhibitory neurotransmitter
link |
that can act as a little bit of a mild sedative
link |
can reduce irritability, et cetera.
link |
But that's just the baseline,
link |
the kind of tide of those neuromodulators.
link |
Again, I want to emphasize that we still have neural circuits
link |
within the brain and body that are specifically releasing
link |
in a very potent way, dopamine, serotonin, and GABA.
link |
So the two things act in concert.
link |
Even though the gut and the brain are acting
link |
both in parallel and directly influencing one another,
link |
it is a powerful synergistic effect.
link |
And there are now hundreds of studies,
link |
maybe even thousands by this point,
link |
mostly performed in animal models, typically mice,
link |
but also some studies in humans
link |
that show that creating the correct environment
link |
for these gut microbiota to thrive
link |
really does enhance mood and wellbeing.
link |
And that when our gut microbiome is not healthy,
link |
that it really can deplete our mood and sense of wellbeing.
link |
Now, there are two major phases
link |
to creating a healthy gut microbiome.
link |
One you can control,
link |
and the other one is less under your control.
link |
I get into this in a lot of detail
link |
in the episode with Dr. Sonnenberg,
link |
which is coming out immediately after this one,
link |
the following Monday, that is.
link |
But for now, I want to just capture
link |
a few of the main points about the early establishment
link |
of the gut microbiome.
link |
It turns out that the environment that we are exposed to,
link |
the things that come into contact with our skin
link |
and digestive tract and any other mucosal lining,
link |
even the urethra, the nasal passages,
link |
any opening to the outside world
link |
that brings in certain, excuse me,
link |
certain microbiota in the first three years of life
link |
is going to have a profound impact
link |
on the overall menu of microbiota
link |
that we will be able to carry within our body.
link |
And it really does seem that getting exposure to
link |
and building a diverse microbiome
link |
in those first three years is critical.
link |
There's a lot of speculation and some data
link |
as to cesarean delivered babies
link |
having less diverse microbiomes
link |
compared to vaginally delivered babies.
link |
There have been attempts, although not conclusive attempts,
link |
to link that to the presence of autism spectrum disorders,
link |
which at least by some statistics
link |
seem to be of higher probability in cesarean deliveries.
link |
Although there are other studies that refute that,
link |
and I want to make that clear.
link |
However, it's clear that babies do not get much,
link |
if any, exposure to microbiota inside of the womb.
link |
Maybe a little bit, but not much.
link |
But that is during the birth process
link |
and in the days and weeks immediately after
link |
they arrive in the world,
link |
that their gut microbiome is established,
link |
that those gut microbiota take residence within the gut.
link |
So it will depend on whether or not
link |
they were breastfed or bottle fed.
link |
It will depend on whether or not
link |
they were exposed to a household pet or not,
link |
whether or not they were held by multiple caregivers
link |
or just by one, whether or not they were a preemie baby
link |
and were contained in a particularly restrictive environment
link |
in order to encourage their further development
link |
before they could be brought home or not.
link |
I don't want to give the picture that if you were isolated
link |
or you were delivered by C-section
link |
that you're somehow doomed to have a poor microbiome.
link |
That's simply not the case.
link |
However, it is the case that the more diversity of microbiota
link |
that one can create early in life is really helpful
link |
for long-term outcomes in terms of brain to gut signaling,
link |
gut to brain signaling,
link |
and for sake of the immune system.
link |
There are some decent studies showing that
link |
if children are exposed to a lot of antibiotic treatment
link |
early in life, that can be very detrimental
link |
to establishment of a healthy gut microbiome.
link |
And fortunately, that reestablishing a healthy gut microbiome
link |
can help rescue some of those deficits.
link |
So doctors nowadays are much more cautious
link |
about the prescription of antibiotic drugs
link |
to children in their early years,
link |
not just up to three years,
link |
but extending out to five and seven and 10 years.
link |
And even in adults, they're very, very careful about that,
link |
or they ought to be.
link |
One reason is the existence, or I would say
link |
the proliferation of antibiotic resistant bacteria
link |
that are becoming more common in hospitals and elsewhere,
link |
and that can cause serious problems.
link |
But in addition to that, because of this understanding
link |
that the gut microbiome is influencing
link |
and actually creating neurotransmitters
link |
that can impact mood and mental health,
link |
impact immune health, and so on.
link |
As I mentioned earlier, there are hundreds,
link |
if not thousands of studies
link |
emphasizing the key role of the microbiome
link |
on brain health, psychiatric health, et cetera.
link |
I want to just highlight a few of those studies,
link |
and in particular, some recent studies that come from labs
link |
that have been working on this sort of thing
link |
for a very long time.
link |
One of the more exciting studies
link |
comes from the work of Mauro Costa-Matioli's lab,
link |
which is at Baylor College of Medicine.
link |
Mauro's lab has been working on mouse models
link |
of autism spectrum disorder for a long time,
link |
and looking at social behavior,
link |
using a mouse model for a long time.
link |
And they've been able to identify
link |
particular types of microbiota
link |
that when they take resonance in the gut
link |
can help offset some of the symptoms of autism,
link |
at least the symptoms of autism
link |
that exist in these mouse models, okay?
link |
So again, this is not human work.
link |
This is work being done on mouse models
link |
for the simple reason
link |
that you can do these kinds of manipulations,
link |
where basically they took mice
link |
that were in germ-free environments
link |
or non-germ-free environments,
link |
or they exposed mice to particular microbiota
link |
and not other microbiota,
link |
and they discovered that a particular microbiota
link |
called L-reuteri, it's L period, R-E-U-T-E-R-I,
link |
treatment with L-reuteri
link |
corrects the social deficits present in these autism models.
link |
And it does so by way of activating our old friend,
link |
but not simply because the vagus nerve
link |
triggers the release of dopamine,
link |
but it turns out that this particular gut microbiota,
link |
L-reuteri, can correct the social deficits
link |
in this autism spectrum disorder model.
link |
It does that by way of a vagal nerve pathway
link |
that stimulates both dopamine release
link |
and oxytocin release.
link |
And they established this really mechanistically
link |
by showing, for instance,
link |
if you get rid of the oxytocin receptor,
link |
you don't see this rescue.
link |
Now, those are mouse models,
link |
so we have to take those with the appropriate grain of salt,
link |
but they're really exciting.
link |
And they come to us in parallel
link |
with other studies that are being done,
link |
taking the microbiomes of people
link |
who have one condition or lack of condition
link |
and putting it into people
link |
who have one condition or another condition.
link |
Let me explain what I mean by that.
link |
The early discovery of the gut microbiome
link |
and its potential to impact health
link |
was not in the context of the gut to brain pathway,
link |
but rather it was in the context of colitis.
link |
This dates back to studies in the 50s,
link |
whereby people with very severe intractable colitis
link |
for which no other treatment was going to work
link |
received fecal transplants.
link |
So yes, that's exactly as it sounds,
link |
taking the stool of healthy people
link |
who do not have colitis,
link |
transplanting those stools into the lower digestive tract
link |
of people who do have colitis,
link |
and they saw significant improvement
link |
if not rescue of the colitis.
link |
That was one of the first indications
link |
that something within stool of all things
link |
could actually rescue another individual from disease,
link |
which sounds kind of wild and crazy
link |
and may even sound disgusting to some of you,
link |
but as I mentioned at the beginning of the episode,
link |
almost 60% of stool is live or dead bacteria, microbiota,
link |
and it really opened up this entire field
link |
of exploring how different microbiota
link |
might have therapeutic effects.
link |
And indeed that has been shown to be the case
link |
also in fecal transplants for certain psychiatric illnesses.
link |
These are still ongoing studies.
link |
They vary in quality.
link |
These are hard studies to do for all sorts of reasons,
link |
getting the appropriate patient populations,
link |
getting agreement, et cetera,
link |
making sure that everything's handled properly.
link |
But what this involves is fecal transplants
link |
from individuals that lack a particular psychiatric condition
link |
or metabolic condition
link |
into people who have a particular metabolic condition.
link |
And there has been tremendous success in some cases.
link |
One of the more powerful and salient examples
link |
There are some people for which,
link |
even if they ingest very low numbers of calories,
link |
even if they go on a liquid protein diet,
link |
simply can't lose weight.
link |
These are somewhat rare disorders,
link |
but these are people that would either do,
link |
get gastric bypass surgery.
link |
Some people are now getting these fecal transplants
link |
from people that have healthy weight
link |
and they take the stool from them,
link |
they put it into lower digestive tract,
link |
and they can see substantial improvement in weight loss
link |
in people that were otherwise unable to do that.
link |
In some cases, actually,
link |
they can start eating relatively normal levels of food
link |
and still lose weight.
link |
So pretty remarkable.
link |
And that tells us there's something in these microbiota
link |
that's really powerful.
link |
Now, how those effects are generated isn't clear.
link |
One idea is that it's impacting the metabolome
link |
components of the metabolism.
link |
Almost certainly that's going to be the case.
link |
Another idea is that it's impacting neurotransmitters,
link |
which change behavior and food choices within the brain.
link |
Although, as I mentioned,
link |
some of these people are already eating very little food
link |
So that's a little bit harder of an argument to create.
link |
There are also some somewhat famous examples now
link |
of how fecal transplants can lead to negative outcomes.
link |
But those negative outcomes further underscore
link |
the power of the microbiome in impacting bodily health.
link |
One key example of this, for instance,
link |
is transfer of fecal matter into another person
link |
in order to treat something like colitis.
link |
And it effectively does that.
link |
But if the donor of the stool of the fecal matter
link |
happened to be obese or have some other metabolic syndrome,
link |
it's been observed that the recipient
link |
can also develop that metabolic syndrome
link |
simply by way of receiving that donor's
link |
particular microbiota.
link |
So these microbiota can create positive outcomes
link |
or they can create negative outcomes.
link |
Now, most of us, of course, are not interested in
link |
or pursuing fecal transplants.
link |
Most people are interested in just creating
link |
a healthy gut microbiome environment
link |
for sake of immune system and brain function.
link |
And we will talk about how to do that
link |
in just a few minutes.
link |
But I just want to further underscore
link |
the power of the microbiota in shaping brain chemistry
link |
and in shaping things like mood
link |
or other aspects of mental health
link |
that typically we don't associate with our gut.
link |
There are several studies published in recent years.
link |
One that I'll just highlight now,
link |
first author, it's Tanya Nguyen, N-G-U-Y-E-N.
link |
The title of the paper is Association of Loneliness
link |
and Wisdom with Gut Microbial Diversity and Composition,
link |
an exploratory study.
link |
It's an interesting study looked at 184 community dwelling
link |
of adults, excuse me, ranging from 28 to 97 years old.
link |
They explored whether or not
link |
having enhanced microbial diversity
link |
somehow related to these variables
link |
that they refer to as loneliness and wisdom.
link |
They used a number of different tests to evaluate those.
link |
Those are common tests in the psychology literature,
link |
not so much in the biology literature,
link |
but nonetheless, there are ways of measuring things
link |
like loneliness and wisdom.
link |
Wisdom in this case being the opposite of loneliness,
link |
at least in the context of this study.
link |
And what they found was the more microbial diversity,
link |
the more diverse one's microbiome was,
link |
the lower incidence of loneliness.
link |
And they did this by taking fecal samples,
link |
profiling them for RNA.
link |
So essentially doing gene sequencing of the stool,
link |
of these individuals,
link |
getting ratings of how lonely or not lonely they felt
link |
and correlating those.
link |
And that's just but one study.
link |
I pointed out because it's particularly recent
link |
and it looked like it was particularly well done.
link |
There is another study that I'll just refer you to.
link |
This was a study published in 2020 in Scientific Reports.
link |
The title of the study is emotional wellbeing
link |
and gut microbiome profiles by enterotype.
link |
What I particularly like about this study
link |
is that they were able to correlate the presence
link |
of certain microbiota
link |
with feelings of subjective wellbeing
link |
and lack of or presence of depressive symptoms.
link |
They did high throughput gene sequencing
link |
of the microbiomes of individuals.
link |
So that meant measuring the microbiota,
link |
figuring out which microbiota were present,
link |
how diverse their microbiome was in general,
link |
gut microbiome diversity is a good thing.
link |
And then to correlate that
link |
with what's called the PANAS score.
link |
PANAS stands for positive affect, negative affect schedule.
link |
This is a test that my lab has used extensively
link |
that other labs use to evaluate mood and wellbeing.
link |
And they defined what were called three enterotypes,
link |
three different categories of people
link |
that ate very different diets
link |
that tended to fall into categories
link |
of having more or fewer emotional symptoms
link |
that were negative
link |
or more or fewer emotional symptoms that were positive,
link |
and whether or not they tend to be more depressed, anxious,
link |
or have more stress-related behaviors, et cetera.
link |
And what they were able to derive from this study
link |
was some strong indications
link |
about what types of things we should ingest in our diet,
link |
maybe even certain things that we should avoid,
link |
but certainly the types of things that we should ingest
link |
that can enhance mood and wellbeing
link |
and can tend to shift people away
link |
from more depressive-like anxiety
link |
and stress-related symptoms.
link |
Before we get into what the particular food items were
link |
that lend themselves to a healthy microbiome,
link |
I want to raise a bigger and perhaps more important issue,
link |
which is what is a healthy microbiome?
link |
I think if you asked any number of world experts,
link |
and I certainly ask this of Dr. Sonnenberg,
link |
what is a healthy microbiome?
link |
They're all going to tell you
link |
it's a microbiome that has a lot of diversity,
link |
that includes a lot of different types of bacteria.
link |
And that makes sense
link |
because it logically would include the bacteria
link |
that produce GABA and dopamine and serotonin
link |
and that support the immune system
link |
and do a number of different things.
link |
But is it simply the case
link |
that adding microbiota diversity is always a good thing?
link |
Well, that doesn't seem to be the case.
link |
Probiotics and prebiotics,
link |
both of which can enhance microbiota diversity,
link |
can improve mood digestion, immune system, and so on.
link |
That's been established,
link |
but it's mainly been established
link |
in the context of post-antibiotic treatment
link |
or people that are recovering from illness
link |
or people that have been very stressed
link |
or have been dealing with all sorts of challenges,
link |
mental or physical,
link |
and they are an attempt to replenish the gut microbiome.
link |
However, it's also clear that excessive microbiota
link |
brought about by excessive intake of probiotics
link |
can lead to things like brain fog.
link |
There's actually some good studies
link |
that point to the fact that certain metabolites
link |
of the microbiome,
link |
certain chemicals produced in the gut and in the body,
link |
can actually lead to brain fog states.
link |
This is thought to come about
link |
through the lactate pathways of the gut
link |
that can then impact the brain.
link |
If you want to look more into this issue
link |
of whether or not probiotics taken in excess, perhaps,
link |
can lead to brain fog,
link |
I'd encourage you to look at a particular paper.
link |
This is a paper published
link |
in Clinical and Translational Gastroenterology,
link |
and the title of the paper
link |
is Brain Fogginess, Gas, and Bloating,
link |
a link between SIBO probiotics and metabolic acidosis.
link |
It was published in 2018.
link |
We can provide a link to this study.
link |
And there are several other studies in the references
link |
that point to the fact that in some cases,
link |
excessive intake of probiotics
link |
and excessive proliferation of gut microbiota
link |
can actually be problematic.
link |
I mention this not to confuse you,
link |
but because it is confusing out there.
link |
We all would think that just increasing
link |
microbiota diversity is always a good thing,
link |
but there are thresholds
link |
beyond which excessive microbiota diversity
link |
might be problematic.
link |
I think everyone agrees
link |
that having too few microbial species living in us
link |
is not a good idea.
link |
Now, none of that answers the questions
link |
that I think everyone really wants answers to,
link |
which are what should we do?
link |
What should we not do to improve our gut microbiome?
link |
I mean, clearly we can't time travel back
link |
to when we were zero to three years old
link |
and get a dog if we didn't have a dog,
link |
get breastfed if we weren't breastfed,
link |
be delivered vaginally as opposed to by C-section
link |
if we didn't have that opportunity,
link |
we just can't time travel and do that.
link |
All of us, however, should be seeking
link |
to improve the conditions of our gut microbiome
link |
because of the critical ways
link |
in which it impacts the rest of our brain
link |
and bodily health.
link |
So what should we do?
link |
What shouldn't we do?
link |
Clearly we know that stress
link |
can negatively impact the gut microbiome.
link |
However, some forms of stress that can quote unquote,
link |
negatively impact the microbiome include fasting,
link |
long periods of fast, which makes sense
link |
because a lot of microbiota need food in order to thrive.
link |
In fact, many, if not all of them do at some point.
link |
There are other questions such as,
link |
should we eat particular foods
link |
and how often should we eat those foods?
link |
We've all been told that fiber is incredibly important
link |
because of the presence of prebiotic fiber,
link |
which can essentially feed the microbiome,
link |
but is fiber really necessary?
link |
And how necessary is it to encourage a healthy microbiome?
link |
Clearly there are a number of people
link |
following relatively low fiber diets,
link |
such as ketogenic diets,
link |
and those can have in some cases anti-inflammatory effects
link |
and can sometimes also improve certain microbiota species.
link |
So it can all be rather confusing.
link |
And for that matter, I asked our resident expert,
link |
Dr. Justin Sonnenberg at Stanford, all of these questions.
link |
And he answers them very systematically in the episode
link |
that comes out after this one.
link |
But I don't want to withhold anything from you.
link |
So I'll just give a very top contour version
link |
and then you'll get more in-depth answers
link |
during that episode.
link |
I asked about fasting.
link |
And the reason I asked about fasting is that years ago,
link |
I was at a meeting
link |
as part of the Pew Biomedical Scholars meeting.
link |
And one of the other Pew Biomedical Scholars
link |
was an expert in gut microbiome.
link |
And I said, hey, are probiotics good for the microbiome?
link |
And if so, which one should I take?
link |
And his answer was very interesting.
link |
He said, you know, in certain cases they can be,
link |
especially if you're traveling or you're stressed,
link |
but it turns out that the particular bacteria
link |
that they put in most probiotics
link |
don't actually replenish the microbiota that you need most.
link |
And I thought, oh, well, why don't they make ones
link |
that replenish the microbiota that you need most?
link |
And his answer was, well, they don't replenish those,
link |
but they replenish other ones that then in turn
link |
encourage the development of the microbiota
link |
that you do want once you start eating
link |
the appropriate foods.
link |
So they changed the environment,
link |
which makes the environment better,
link |
which indirectly supports the proliferation
link |
of quote unquote good microbiota.
link |
Okay, so that was a somewhat convoluted answer,
link |
but I did appreciate his answer.
link |
Then I asked him about fasting.
link |
I said, well, a lot of people are getting interested
link |
in intermittent fasting now.
link |
People are spending a significant portion
link |
of each 24 hour cycle avoiding food
link |
for sake of time restricted feeding.
link |
What does that do to the gut microbiome?
link |
Does it make it healthier or does it make it unhealthier?
link |
Well, my colleague from Yale and Dr. Sonnenberg
link |
both confirmed that during periods of fasting,
link |
especially prolonged periods of fasting,
link |
we actually start to digest away
link |
much of our digestive tract.
link |
Now, the whole thing doesn't start to disappear,
link |
but there's thinning of the mucosal lining
link |
or at least disruption of the mucosal lining.
link |
A lot of the microbiota species can start to die off.
link |
And so it was surprising to me,
link |
but nonetheless interesting that fasting
link |
may actually cause a disruption to certain healthy elements
link |
of the gut microbiome.
link |
But again, there's a caveat.
link |
The caveat is that when people eat after a period of fast,
link |
there may be a compensatory proliferation,
link |
meaning an increase in healthy gut microbiota.
link |
So you start to get the picture
link |
that fasting is neither good nor bad.
link |
You start to get the picture that particular diets,
link |
meaning certain restriction diets
link |
or macronutrient rich diets may not be good or bad
link |
for the microbiome.
link |
And yet there are some answers that arrive to us
link |
from Dr. Sonnenberg, but from other experts in the field,
link |
that there are certain foods
link |
and certain things that we can ingest,
link |
which definitely enhance the microbiome
link |
and make it healthier than it would be
link |
were we to not ingest those foods.
link |
So next I'd like to talk about
link |
what I think is a really pioneering
link |
and important study in this area.
link |
This is a study that was carried out by the Sonnenberg lab
link |
in collaboration with Chris Gardner's lab,
link |
also at Stanford, where they compared
link |
two general types of diets in humans,
link |
diets that were fiber rich,
link |
which has been proposed time and time again
link |
to enhance microbiota diversity
link |
and to enhance gut brain signaling even
link |
and to enhance the immune system, perhaps,
link |
and diets that were enriched
link |
in so-called low sugar fermented foods.
link |
Before I dive into that study and what the conclusions were,
link |
because they are very interesting
link |
and very actionable for all of us,
link |
I do want to touch on probiotics
link |
because I want to avoid confusion.
link |
It is not the case that ingestion of probiotics
link |
will always lead to brain fog.
link |
I want to make that clear.
link |
It is the case that ingestion of probiotics,
link |
even if those probiotics don't directly contain
link |
the microbiota species that one is trying to proliferate,
link |
can be useful for improving microbiota diversity.
link |
In general, it seems that maintaining
link |
a healthy gut microbiome involves ingesting
link |
certain types of foods,
link |
and we'll talk about those in a moment,
link |
but perhaps also augmenting the microbiota system
link |
through prebiotics or probiotics
link |
at a fairly low level on a consistent basis.
link |
So these are not high dose probiotics
link |
except under conditions of dysbiosis,
link |
where, for instance,
link |
if somebody has done a round of antibiotics
link |
and they need to replenish their gut microbiome,
link |
there are foods and there are pill form
link |
and powder form prebiotics and probiotics
link |
that can be very useful,
link |
or in cases where people have been very stressed
link |
or are undergoing excessive travel
link |
or have shifted their diet radically,
link |
maybe that's due to travel, maybe that's due to illness,
link |
maybe that's due to stress,
link |
but when there are a number of different converging events
link |
that are stressing or depleting microbiota diversity,
link |
that's when, at least I believe,
link |
it can be useful to support the gut microbiome
link |
through the ingestion of quality probiotics or prebiotics.
link |
So it would be under conditions where people are stressed
link |
or their system is generally stressed
link |
for environmental or illness-related reasons,
link |
that it might be useful to lean towards higher doses
link |
of prebiotics or probiotics than one might normally use,
link |
but that under normal conditions,
link |
that one would focus on quality nutrients through diet
link |
and focus on ingestion of probiotics
link |
at a fairly low to moderate level
link |
and or prebiotics at a fairly low to moderate level.
link |
That just seems like the logical approach
link |
based on the experts that I've spoken to,
link |
but certainly if your doctor prescribes
link |
or suggests that you take high levels of probiotics
link |
you should definitely pay attention to your physician
link |
and you should obviously pay attention to your physician.
link |
In any case, you should never add or remove anything
link |
from your nutritional plan or supplementation plan
link |
without consulting a physician.
link |
So what should we do in order to maximize the health
link |
of our gut brain axis, as it's called?
link |
How should we support the diversity of the good microbiota
link |
that help us create all these neurotransmitters
link |
that we want, improve our immune system function,
link |
and so on and so forth?
link |
Well, some of that is going to be through the basics.
link |
When I say the basics, I mean the foundational things
link |
that really set us up for overall health.
link |
So this is going to be getting deep sleep
link |
of sufficient duration 80 plus percent of the time.
link |
I mean, if you could get 100% of the time, that'd be great,
link |
but very few people accomplish that.
link |
It's going to be proper hydration.
link |
It's going to be proper social interactions.
link |
It's going to be proper nutrition.
link |
And we'll talk more about nutrition in a moment.
link |
It's going to be limiting excessive prolonged stressors
link |
And indeed we've done episodes about
link |
just about all of those things, but certainly about stress.
link |
We have an episode of the Huberman Lab podcast
link |
that you can find at HubermanLab.com
link |
all about mastering stress,
link |
how to avoid long periods of intense stress,
link |
what to do to offset those.
link |
Given that stress can disrupt the microbiome,
link |
whether or not you're fasting or not,
link |
those tools ought to be useful.
link |
Now, in what I consider to be a landmark study
link |
exploring the relationship between the gut microbiome,
link |
food intake, and overall health
link |
is this paper from Justin Sonnenberg's lab
link |
and Chris Gardner's lab, both of which are at Stanford.
link |
And the paper entitled,
link |
Gut Microbiota Targeted Diets Modulate Human Immune Status
link |
was published in the journal Cell,
link |
which is among the three top journals,
link |
perhaps in the world, Nature, Science, and Cell
link |
really being the apex journals for overall science,
link |
and especially for biomedical sciences.
link |
Now, this is a very interesting study.
link |
It was done on humans.
link |
There were two major groups.
link |
One group of humans was instructed
link |
to increase the amount of fiber in their diet
link |
and in fact ate a high fiber diet.
link |
The other group was instructed
link |
to eat a high fermented food diet.
link |
Now, both groups started off not having eaten
link |
a lot of fiber or a lot of fermented foods,
link |
and were told to increase the amount of either fiber
link |
or fermented foods that they were ingesting
link |
over a four-week ramp up period.
link |
And that was to avoid any major gastric distress.
link |
It turns out that if you're not already accustomed
link |
to eating a lot of fiber, increasing your amount of fiber
link |
dramatically can cause some gastric distress.
link |
But if you ease into it over time, as we'll see,
link |
there's a mechanism behind this,
link |
which was unveiled in this study.
link |
But if you ease into it over time,
link |
then the system can tolerate it.
link |
Likewise, high fermented foods can be readily tolerated
link |
if there's a ramp up phase of ingesting
link |
maybe one serving a day, then maybe two servings,
link |
and ramping up, in this case,
link |
as high as six servings per day.
link |
However, after this ramp up period,
link |
the group assigned to the high fiber condition
link |
maintained high fiber intake for six weeks,
link |
and the high fermented food group
link |
maintained high fermented food intake for six weeks,
link |
after which they went off either the high fiber
link |
or the high fermented food diet,
link |
and there was a four-week follow-up period
link |
during which they gradually returned to baseline.
link |
Throughout the study, their gut microbiome
link |
was evaluated for the diversity of gut microbiota,
link |
and there were also a number of measures
link |
of immune system function,
link |
in particular measures of the so-called inflammatome.
link |
The immune system has a lot of different molecules involved.
link |
I did a whole episode about the immune system.
link |
If you're interested in learning
link |
what some of those molecules are,
link |
various cytokines and signaling molecules
link |
that reflect either high inflammation states
link |
or reduced inflammation states in the brain and body,
link |
you're welcome to check out that episode.
link |
It's also at hubermanlab.com.
link |
Regardless, in this study,
link |
they explored the sorts of immune markers
link |
that were expressed in either of the two groups
link |
and compared those.
link |
The basic takeaway of this paper
link |
was that contrary to what they predicted,
link |
the high fiber diet did not lead
link |
to increased microbiota diversity,
link |
at least not in all cases,
link |
and that was somewhat surprising.
link |
You know, the idea is that prebiotic fiber
link |
and a lot of the material in fruits and vegetables
link |
and grains and so forth
link |
are supposed to support microbiota diversity
link |
and the proliferation of existing microbiota,
link |
and that is not what they observed.
link |
Although I want to be very clear in pointing out
link |
that the results do not indicate
link |
that fiber is not useful for health overall,
link |
but it does point to the fact
link |
that increasing fiber intake
link |
did not increase microbiota diversity,
link |
which in general, as I mentioned before,
link |
is associated with improvements in microbiota function,
link |
health, and overall wellbeing.
link |
Now, the high fermented food diet condition
link |
was very interesting.
link |
It resulted in increased microbiome diversity
link |
and decreased inflammatory signals and activity.
link |
So there was a twofer,
link |
basically by ingesting high fermented foods
link |
in fair abundance, right?
link |
You know, four to six servings or more per day
link |
is a lot of fermented food intake.
link |
We'll talk about what some of those foods were,
link |
but the outcome was very positive.
link |
There was a clear increase in microbiome diversity
link |
and decreased inflammatory signals.
link |
So things like interleukin-6,
link |
a number of other interleukins and cytokines
link |
that are associated with increased inflammation
link |
in the brain and body were reduced significantly.
link |
Now, let's talk a little bit about this notion
link |
of number of servings, et cetera.
link |
One somewhat minor point of the study,
link |
but I think is useful in terms of taking
link |
an actionable stance with this,
link |
is that the number of servings of fermented foods
link |
was not as strong a predictor of improvements
link |
in the inflammatome, meaning reduced inflammation,
link |
and improvements in microbiota diversity,
link |
as was the duration of time that the individuals
link |
were ingesting fermented foods.
link |
In other words, the longer that one is consistently
link |
ingesting fermented foods on a daily basis,
link |
the better the outcomes in terms of the gut microbiome
link |
and for reducing inflammation.
link |
So I think that's an important point.
link |
And I make that point especially because
link |
for a lot of people, even if you do this ramp up phase,
link |
six servings per day of fermented foods
link |
can seem like quite a lot.
link |
So what are these fermented foods, right?
link |
I think many of us are familiar with certain cheeses
link |
and being fermented and beer being fermented
link |
and kombucha is fermented.
link |
In this study, they focus specifically
link |
on low sugar fermented foods.
link |
So this would be plain yogurt,
link |
in some cases, kimchi or sauerkraut.
link |
An important consideration, however,
link |
is that it needs to contain
link |
what are called live active cultures,
link |
which means there actually have to be microbiota
link |
that are alive inside the sauerkraut.
link |
One way you know whether or not that's happening
link |
is if you purchase sauerkraut or pickles or kimchi
link |
from a jar or a container that's on the non-refrigerated
link |
shelf or the non-refrigerated section of your grocery store,
link |
it is not going to contain live active cultures
link |
And likewise, if you consume yogurt that has a lot of sugar
link |
or other components added to it,
link |
it's not going to have the same positive effect
link |
on the microbiome, at least that's the prediction
link |
given some of the relationship between
link |
the sorts of microbiota that live in sugar
link |
versus plain type yogurts.
link |
They gave people the option of consuming
link |
any number of different low sugar fermented foods.
link |
So again, that could be sauerkraut, kimchi,
link |
things like kefir, natto.
link |
In Japan, they consume natto, which is a fermented food.
link |
Beer was not one of the fermented foods
link |
that was included in the fermented food list.
link |
And when we say six servings per day,
link |
that is indeed six ounce servings
link |
or four to six ounce servings.
link |
It was not six servings of what's listed on the package.
link |
So again, that turns out to be
link |
a fair amount of fermented foods.
link |
How should you gauge whether or not
link |
you're getting enough of this?
link |
Well, if you decide to take on this protocol
link |
of ingesting more fermented foods,
link |
which at least by my read of this study
link |
and some of the follow-up work that's being done,
link |
sounds like a terrific idea.
link |
If you want to improve your gut microbiome
link |
for all the great reasons that one would want to,
link |
brain, body, health, reduced inflammation and on and on.
link |
Well, then you definitely want to focus on fermented foods
link |
that you enjoy consuming.
link |
So for you, if that's kefir or for you that's plain yogurt
link |
or for you that's sauerkraut,
link |
which happens to be my personal favorite,
link |
then you want to make sure that it's going to be something
link |
that you are going to enjoy ingesting quite a lot of
link |
and that you're going to be okay with ingesting
link |
probably throughout the day.
link |
Now, people follow different meal schedules, of course,
link |
but this does require not just eating
link |
all the fermented foods just before bedtime or one meal.
link |
I suppose you could do that,
link |
but in general, it's going to work best
link |
in terms of limiting gastric distress
link |
by spreading it out throughout the day.
link |
I also want to mention brine.
link |
Brine is the liquid that surrounds sauerkraut.
link |
It's that very salty fluid,
link |
and that contains a lot of active live cultures.
link |
And they did include,
link |
or they allowed people to include brine in this study.
link |
And in discussions with Dr. Sonnenberg,
link |
which we'll go into in more detail on the episode
link |
that comes out next week,
link |
we talk a lot about the particular value
link |
that brine might hold
link |
in terms of bringing about microbiota diversity
link |
because of the richness of live cultures that it contains.
link |
I do want to focus for a moment on the high fiber condition
link |
because there were some interesting observations
link |
about the people that were placed into that condition.
link |
First of all, increasing the amount of fiber
link |
definitely increased the number of enzymes
link |
that can be used to digest fiber.
link |
This is in keeping with this idea of this ramp up phase
link |
where accumulation of more fiber intake
link |
can over time lead to less gastric distress,
link |
but also to more utilization of fiber,
link |
which overall should be a good thing.
link |
So while they didn't observe an increase
link |
in immune system function
link |
or an increase in microbiota diversity,
link |
there was an increase in these fiber digesting enzymes.
link |
They also observed
link |
what they called personalized immune responses.
link |
There were some subgroups within the high fiber group
link |
that had interesting changes in terms of their reactions to,
link |
or I should say their inflammatome,
link |
meaning the inflammatory markers they expressed
link |
as well as their microbiota diversity.
link |
So there were essentially three groups.
link |
One group actually showed an increase in inflammatory markers
link |
so that was quite surprising
link |
and probably not wonderful for the message
link |
that fiber is always good for us,
link |
but that was a small cohort within the fiber intake group.
link |
Another group and still another group
link |
both showed reductions in baseline microbiota diversity,
link |
although to varying degrees.
link |
So I don't want to paint the picture that fiber is bad,
link |
but fiber certainly did not have the positive effects
link |
on microbiota diversity
link |
that the high fermented food diet did.
link |
So my read of this study,
link |
and I think the stance that many others have taken
link |
as a consequence of these data,
link |
is that we should be increasing our fermented food intake,
link |
that that's simply a good thing to do
link |
in order to support our gut microbiome
link |
and to reduce inflammatory signals in our brain and body.
link |
And there are a number of different ways to do that.
link |
I mentioned some of the particular foods.
link |
However, anytime you're talking about
link |
ingesting fermented foods,
link |
especially the high quality ones
link |
that come from the refrigerated section of the grocery store
link |
or that end that have low sugar content, et cetera,
link |
we do have to be considerate of cost
link |
because certain things like kombuchas, for instance,
link |
can be quite costly.
link |
I should also mention some kombuchas
link |
that actually contain alcohol.
link |
Some do not or contain very little amounts of alcohol.
link |
One way to avoid the high cost of fermented foods
link |
while still being able to accumulate
link |
a lot of fermented food intake
link |
is to simply make those fermented foods yourself.
link |
This is something that we've started exploring
link |
and experimenting with in our home.
link |
One simple way to do this
link |
is to just make your own sauerkraut.
link |
It involves very few ingredients.
link |
It basically involves cabbage, water, and salt,
link |
but there's a specific process that you need to follow
link |
in order to create these large volumes of sauerkraut at home
link |
using that low cost method.
link |
The best resource that I know of
link |
in order to follow a great recipe to make homemade sauerkraut
link |
would be the recipe for homemade sauerkraut
link |
that's contained in Tim Ferriss' book,
link |
"'The 4-Hour Chef.'"
link |
There's an excellent protocol there.
link |
It involves chopping up the cabbage,
link |
putting into a bowl, mashing it up with your hands,
link |
putting water in there, some salt, covering it,
link |
and then keeping it in a particular environment,
link |
and then routinely scraping off
link |
some of the material from the surface.
link |
You have to do that in order to make sure
link |
that you're not getting microbes and things growing in it
link |
that are bad for you,
link |
so you definitely want to pay careful attention
link |
but that's a very, very low cost way
link |
of generating lots and lots of fermented foods
link |
so you don't go broke trying to improve your microbiome.
link |
The other thing that you can do
link |
if you're really obsessed with kombucha
link |
or something like that to avoid the high cost of kombucha
link |
is there are ways that you can get the SCOBY,
link |
which basically allows you to make
link |
your own kombucha at home.
link |
I've never tried this,
link |
but when I was a postdoc,
link |
there was an undergraduate in the lab.
link |
I think, well, I won't out him,
link |
but he's now gone on to medical school,
link |
and I think he's passed his residency
link |
and is a practicing doctor,
link |
but nonetheless, he was always making kombucha at home.
link |
He told me it was exceedingly easy,
link |
but then again, he had a number of other skills
link |
and attributes that made me think
link |
that he could do pretty much anything with ease,
link |
whereas I tend to struggle with even basic cooking.
link |
So maybe if you're feeling a little more adventurous,
link |
you could explore making your own kombucha,
link |
but there are a number of different protocols
link |
and recipes out there
link |
for making your own low sugar fermented foods.
link |
So you needn't run out
link |
and buy fresh sauerkraut all the time.
link |
I should also mention for those of you
link |
that are interested in getting your fermented intake
link |
from pickles, jarred pickles rarely,
link |
if ever contain ferment.
link |
Mostly they're just soaked in vinegar water
link |
and with some spices,
link |
but there are some that contain ferment.
link |
You actually have to look for that on the container
link |
and I don't know, maybe someone out there
link |
knows how to make natto and knows how to make kimchi well
link |
and things of that sort.
link |
It certainly is the case based on the data from the study
link |
that ingesting more servings of fermented food per day
link |
ought to be beneficial for our gut microbiome.
link |
And since this is an episode,
link |
not just about gut microbiome, but gut brain health,
link |
I should mention that one form of signaling
link |
between the gut microbiome and the brain,
link |
which we did not discuss,
link |
and I'll just touch on briefly,
link |
is that when the inflammatome
link |
or the genes and markers of inflammation
link |
are kept in a healthy range,
link |
there's an active signaling
link |
of that immune system status to the brain.
link |
There's an intermediate cell type
link |
that communicates immune status to the brain.
link |
And that cell type is the microglial cell.
link |
It's a type of glia as the name suggests.
link |
When there's a lot of inflammation in the body,
link |
these microglia actually get activated
link |
and can start eating away at various components
link |
of the brain and nervous system.
link |
And I don't mean massive eating away.
link |
They're not going to digest the whole brain,
link |
but these microglia are sort of the resident macrophages
link |
Macrophages are in the periphery
link |
and they gobble up debris and things of that sort.
link |
The microglia on a regular basis are eating up debris
link |
that accumulates across waking cycles
link |
and in response to micro damage of the brain
link |
that occurs on a daily basis.
link |
So they have a lot of important basic everyday
link |
what we call housekeeping functions.
link |
But when there's a lot of inflammation in the body,
link |
when there's a massive immune response,
link |
the microglia can be hyperactivated
link |
and that's thought to lead
link |
to any number of different cognitive defects
link |
or challenges, thinking,
link |
or maybe even some forms of neurodegeneration over time.
link |
Although that last point is more of a hypothesis
link |
than a well tamped down fact at this point.
link |
There's still a lot of investigation to be done in humans.
link |
The animal data, however, are very, very strong
link |
that when the immune system is activated
link |
or chronically activated or hyperactivated,
link |
that neural tissue, meaning brain tissue,
link |
and other central nervous system tissue can suffer.
link |
So there are a lot of reasons
link |
to want to not just improve microbiome diversity,
link |
but to also improve immune system function
link |
and to limit the number of inflammatory markers
link |
that are present in the body
link |
because of the way those inflammatory markers
link |
can signal deleterious events in the brain.
link |
And while eating fermented foods
link |
and making your own fermented foods
link |
and buying high quality fermented foods
link |
might seem like an inconvenience,
link |
I would say that from the perspective of cost benefit
link |
or effort benefit, it's actually quite a good situation
link |
where if you can just ramp up the number of fermented foods
link |
or servings of fermented foods that you're eating per day
link |
over a period of a few weeks
link |
so that you're tolerating that well,
link |
that ought to have a very positive effect
link |
on your microbiome diversity
link |
and indeed on gut brain function.
link |
And I'll be the last to suggest
link |
that people completely forgo on fiber.
link |
I think there's some debate out there
link |
as to how much fiber we need
link |
and whether or not certain forms of fiber
link |
are better than others.
link |
I'm not going to get into that debate.
link |
It's barbed wire enough
link |
without me injecting my own views into that debate.
link |
But I think there's ample evidence to support the fact
link |
that for most people,
link |
ingesting a fair amount of fiber is going to be a good idea.
link |
I would just say that make sure
link |
that you're also ingesting a fair amount of fermented foods.
link |
And along the lines of fiber,
link |
in an accompanying article published in Cell,
link |
which was sort of what we call a news and views piece
link |
about the Sonnenberg and Gardner paper,
link |
they make a quite good point,
link |
which is that the increase in fiber intake
link |
that led to this increase in carbohydrate active enzymes,
link |
these CAZ-zymes as they're called,
link |
these are enzymes that help digest fiber,
link |
quote, indicating an enhanced capacity for the microbiome
link |
to degrade complex carbohydrates present in fibrous foods.
link |
So in other words,
link |
eating more fiber and fibrous foods
link |
allowed for an increase in these enzymes
link |
that allow you to eat still more fibrous foods
link |
or to better digest fibrous foods
link |
that are coming in through other sources.
link |
So there is at least one utility for increasing fiber,
link |
even though it's separate from the gut microbiota diversity
link |
and reducing inflammation.
link |
And I'd be remiss if I didn't touch on some of the data
link |
and controversy about artificial sweeteners
link |
and the gut microbiome.
link |
I want to be very clear that what I'm about to tell you
link |
has only been established in animal models,
link |
in a mouse model, at least to my knowledge.
link |
What the studies have shown, and there were several,
link |
but one published in the journal Nature a few years back
link |
is the one that got the most amount of attention,
link |
is that animals that consume large amounts
link |
of artificial sweeteners,
link |
in particular things like saccharin or sucralose,
link |
show disruptions in their gut microbiome.
link |
I'm not aware of any studies in humans
link |
that show the equivalent effect,
link |
and I'm not aware of any studies in humans
link |
that show the equivalent effect
link |
for things like plant-based low calorie sweeteners,
link |
things like stevia, monk fruit, and things of that sort.
link |
And at least by my exploration,
link |
I couldn't find any data specifically related
link |
to the sweetener aspartame.
link |
So right now it's somewhat controversial,
link |
and actually this is kind of a third rail topic out there
link |
when one group will come out saying
link |
that artificial sweeteners are bad
link |
because they disrupt the gut microbiome.
link |
The response generally from a number of people as well,
link |
that's only been shown in animal models,
link |
and indeed that's true.
link |
So right now I don't think that there's a strong case
link |
one way or the other.
link |
I think that people should basically ask themselves
link |
whether or not they like artificial sweeteners or not,
link |
whether or not they're willing to risk it or not,
link |
and obviously that's an individual choice.
link |
I also want to point out a recent study
link |
from Diego Bajorquez's lab,
link |
which actually shows, however,
link |
that neurons in the gut, those neuropod cells,
link |
are actually capable of distinguishing
link |
between real sugars and artificial sweeteners.
link |
This is a really interesting body of work.
link |
It was published just recently, I should say, February, 2022.
link |
The title of the paper is
link |
"'The Preference for Sugar Over Sweetener'
link |
Depends on a Gut Sensor Cell."
link |
And to make a long story short,
link |
what they showed was there's a category of neuropod cells
link |
that recognize sugar in the gut
link |
and signal that information
link |
about the presence of sugar in the gut
link |
to the brain via the pathways we talked about before,
link |
the nodose ganglia, the vagus, dopamine, et cetera, et cetera.
link |
Interestingly, the very same category of neurons
link |
can respond to artificial sweeteners
link |
and signal that information to the brain,
link |
but the pattern of signaling,
link |
and indeed the signature pattern
link |
that is conveyed to the brain and received by the brain
link |
is actually quite a bit different
link |
when these same neurons are responding
link |
to artificial sweeteners versus actual sugar.
link |
This is very interesting because what it means is,
link |
first of all, that neurons have incredible specificity
link |
in terms of what they are signaling
link |
from the gut to the brain.
link |
And it also means that there may be a particular signal
link |
that the brain receives that says,
link |
I'm receiving some intake of food or drink that tastes sweet
link |
but doesn't actually offer much nutrients
link |
in the direction of sweetness,
link |
meaning that it doesn't have calories despite being sweet.
link |
Now, again, this is all subconscious processing.
link |
And like with the previous studies,
link |
we were just discussing about artificial sweeteners
link |
generally and the gut microbiome generally,
link |
it's unclear how this relates to humans
link |
at this point in time.
link |
But given the similarity of cellular processes
link |
and molecular processes at the level of gut brain in mice,
link |
I think it stands to reason that these neuropod cells
link |
very likely are capable of signaling presence
link |
of real sweetener versus artificial sweetener
link |
in humans as well,
link |
although that still remains to be determined empirically.
link |
So I'd like to just briefly recap what I've covered today.
link |
I started off by talking about the structure and function
link |
of the gut brain axis.
link |
I described the basic structure and function
link |
of the digestive pathway
link |
and how that digestive pathway harbors microbiota species,
link |
meaning many, many little bacteria
link |
that can signal all sorts of things
link |
to the rest of the brain and body.
link |
And indeed, we talked about the various ways
link |
that they do that.
link |
We talked about direct pathways,
link |
literally nerve networks that extend from the gut
link |
up to the brain and from the brain back to the gut.
link |
And we talked about indirect pathways,
link |
how some of the gut microbiota
link |
can actually synthesize neurotransmitters
link |
that get out into the bloodstream, can impact the body,
link |
can impact the immune system,
link |
and can get into the brain
link |
and act as neurotransmitters in the brain,
link |
just as would neurotransmitters
link |
that originate from within the brain.
link |
We also talked about what constitutes
link |
a healthy versus unhealthy microbiome.
link |
And it's very clear that having a diverse microbiome
link |
is healthier than having a non-diverse microbiome.
link |
But as I pointed out, there's still a lot of questions
link |
as to exactly what microbiota species you want to enhance
link |
and which ones you want to suppress in the gut
link |
in order to achieve the best gut brain access function.
link |
We talked about how things like fasting
link |
might impact the microbiome
link |
and how some of that might be a little bit counterintuitive
link |
based on some of the other positive effects of fasting,
link |
or if we're not just discussing fasting,
link |
some other types of somewhat restrictive diets,
link |
either restrictive in time
link |
or restrictive in terms of macronutrient intake,
link |
how those may or may not improve
link |
the health of the gut microbiome.
link |
And the basic takeaway was that
link |
because we don't know exactly how specific diets
link |
impact the gut microbiome,
link |
and we don't know how fasting
link |
either promotes or degrades the microbiome,
link |
we really can't say whether or not they are improving
link |
or degrading the microbiome at this time.
link |
However, it is clear that stress,
link |
in particular chronic stress,
link |
can disrupt the gut microbiome.
link |
It's also clear, of course,
link |
that antibiotics can disrupt the gut microbiome.
link |
And that brings us to the topic
link |
of prebiotics and probiotics.
link |
And I emphasize the fact that for most people,
link |
ingesting high quality non-processed foods
link |
that includes some prebiotic fiber,
link |
but also that includes some probiotics
link |
will probably be healthy,
link |
but not excessive levels of probiotics.
link |
High levels of supplemented probiotics
link |
of the sort that would come in a probiotic pill
link |
or even prescription probiotics
link |
would probably lend themselves best
link |
to when people were under severe chronic stress
link |
or had just come off a serious round
link |
or an ongoing or repeated rounds of antibiotics.
link |
That does not mean that ingesting probiotics
link |
in any form or any kind is not good.
link |
It just means that the very high dose probiotics,
link |
again, typically found in prescription form
link |
or capsule pill form,
link |
probably are best reserved to cases where,
link |
of course, your doctor prescribes them.
link |
You should always follow your doctor's advice.
link |
But in cases where perhaps you are jet lagged,
link |
you're traveling excessively for any reason
link |
or working excessively, you're not getting enough sleep,
link |
or your diet is radically changed from normal.
link |
And we talked about how increasing the amount of fiber
link |
in your diet might be useful
link |
for increasing fiber digesting enzymes
link |
and the assimilation of fibrous foods,
link |
but that it's really the ingestion of fermented foods.
link |
And in fact, getting anywhere from four
link |
or even up to six servings a day of fermented foods
link |
can be immensely beneficial
link |
for reducing inflammatory markers in the body
link |
and for improving microbiota diversity all along the gut
link |
and thereby improving signaling
link |
and outcomes along the gut brain axis.
link |
So we went all the way from structure to function
link |
to the four kinds of signaling, mechanical, chemical,
link |
indirect, direct, probiotics, fiber, and fermented foods.
link |
And I tossed in a little bit at the end there
link |
also about ways that you can make your own fermented foods
link |
at home in order to try and offset some of the costs.
link |
Also, it's just kind of fun to do.
link |
And some of those actually taste quite good.
link |
I've actually found that the fermented sauerkraut
link |
that we're making at home actually rivals the sauerkraut
link |
that you can buy out of the refrigerated section
link |
at the grocery store.
link |
And I am by no means a skilled cook or chef
link |
and basically have no culinary skill whatsoever.
link |
So if I can do it, you can do it.
link |
I hope you found this information useful
link |
and perhaps also actionable.
link |
One of my motivations for doing this episode
link |
was, again, as a primer for the episode
link |
with Dr. Justin Sonnenberg,
link |
where we go really deep into the gut microbiome,
link |
less so into the gut brain axis,
link |
but really deep into the gut microbiome,
link |
what it is, what it does, what it doesn't do,
link |
and some of the emerging findings from his lab
link |
that are yet to be published.
link |
And I also was excited to do this episode
link |
because I think many of us have heard
link |
about the gut microbiome.
link |
We hear about these bacteria that live in our gut.
link |
We hear about the gut brain axis
link |
or that 90% or more of the serotonin
link |
that we make is made in our gut.
link |
We hear about the gut as a second brain and so forth.
link |
But I think for many people,
link |
they don't really have a clear picture
link |
of what the gut microbiome is
link |
and the pathways and mechanisms by which it can signal
link |
to the brain and to the other parts of the body.
link |
So I hope that today's information
link |
at least improved the clarity around that topic
link |
and leaves you with a more vivid picture
link |
of this incredible system that is our gut brain axis.
link |
If you're enjoying and or learning from this podcast,
link |
please subscribe to our YouTube channel.
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In addition, please subscribe to the podcast
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And on Apple, you can leave us up to a five-star review.
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Please, of course, give us feedback and comments,
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That's perhaps the best way to support this podcast.
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And we have a Patreon.
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and there you can support the podcast
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On many previous episodes of the Huberman Lab Podcast,
link |
we talk about supplements.
link |
While supplements aren't necessary for everybody,
link |
many people derive tremendous benefit from them.
link |
One of the key issues with supplements, however,
link |
is that the quality of supplements can vary tremendously
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and oftentimes that relates to the precision,
link |
or I should say the lack of precision
link |
with which companies put different amounts of supplements
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in the capsules and tablets than are listed on the bottle.
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For that reason, we partnered with Thorne, T-H-O-R-N-E,
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That is, what is listed on the bottle is actually
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If you'd like to see the Thorne supplements that I take,
link |
you can go to Thorne, that's thorne.com,
link |
slash the letter U slash Huberman,
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You can get 20% off any of those supplements,
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it's also Huberman Lab on Twitter,
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link |
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