Welcome to the Huberman Lab Podcast,
where we discuss science
and science-based tools for everyday life.
My name is Andrew Huberman,
and I’m a professor of neurobiology and ophthalmology
at Stanford School of Medicine.
This podcast is separate
from my teaching and research roles at Stanford.
It is, however, part of my desire and effort
to bring zero cost to consumer information
about science and science-related tools
to the general public.
In keeping with that theme,
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I’ve done a couple of episodes now
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Today, we’re talking all about emotions.
Emotions are central to our entire experience of life.
Whether or not we’re happy or sad or depressed or angry
is our life experience.
And yet, I think with all the importance
that we’ve placed on emotions,
very few people actually understand
how emotions arise in our brain and body.
And I mentioned brain and body,
because as you’ll see today,
emotions really capture the brain-body relationship.
We cannot say that emotions arise
just from what happens in our head.
It also involves events, biological events,
chemical events within our body.
The other thing about emotions
is that there’s no real agreement
as to what’s a good emotion or a bad emotion.
Today, we’re going to talk about the biology
of the chemicals and pathways that give rise to emotions.
And I’m going to equip you with several, if not many, tools
that will allow you to regulate and change
and steer your emotions should you want,
but not using the typical advice.
You know, everyone’s probably heard of this thing.
Oh, you know, if you’re feeling depressed, just smile.
You know, it’s impossible to be depressed while smiling.
Look, if that were true,
we wouldn’t have any depressed people,
because depressed people don’t want to be depressed.
And it is not the case that simply smiling
will reverse depression or sadness.
And it’s simply not the case
that smiling can inhibit sadness.
It just doesn’t work that way.
However, it is the case that certain things
that are happening in our body
influence how our brain functions
and the chemicals that are released.
And today, we’re going to talk a lot
about how the brain and body interact
to create these things called emotions
in the context of food and nutrition.
And the reason we’re doing that
is not because I am beating the drum
about particular diet regimens or anything.
In fact, I’m not going to do any of that.
What I’m going to do is I’m going to review
some of the most important scientific data
that point to how ingesting certain nutrients,
both macronutrients like proteins, fats, and carbohydrates,
as well as micronutrients,
can impact the chemicals in our brain
that give rise to the feelings of being happy
or sad or sleepy or alert when you want to be sleepy
or sleepy when you want to be alert.
So this is sure to be a broad discussion,
and yet we’re going to get very specific
about what emotions are, how they arise in the body,
tools that one can use
in order to better control their emotions,
tools that people can use to, believe it or not,
feel happier or feel calmer.
And that’s because in the last 20 years or so,
there’s been an explosion of scientific studies
exploring how the brain and body interact
to support certain neurochemicals
that give us these feelings of being alert and happy
or depressed or certain that our life
is going to be terrible
or certain that our life is going to be great.
So as mysterious as all that might sound
and confusing as all that might sound,
we’re going to make it very clear today.
And you’re going to come away from this conversation
with a lot of tools that you can act on immediately.
And those tools are grounded in scientific data.
We are going to provide links to several of the studies,
and I’m going to mention several of those studies
as we go along.
But overall, the goal today is for you to understand
how moods and emotions arise
and the different pathways in your brain and body
that allow them to happen
and how you can use those pathways to change those emotions
and the tools that you can rely on in very specific ways
to shift from being, say, slightly depressed
to feeling happier.
There actually are ways to do that,
or from feeling too alert and anxious to feeling calmer.
And these are tools that are distinct
from the tools I’ve talked about in previous episodes.
The discussion around emotions has a long and rich history,
going back to Darwin and even long before Darwin.
This is a conversation that philosophers and scientists
have been having for hundreds, if not thousands of years.
The idea that Darwin put forth
and that was really attractive for about the last 100 years
was that emotions are universal
and that some of the facial expressions
around emotion are universal.
And other people have capitalized on that idea.
And to some extent, it’s true.
I mean, I think that the two most robust examples of that
would be when we see something or we smell something
or we taste something that we like,
there does tend to be a postural leaning in.
We tend to inhale air at that time.
We tend to bring in more
of whatever chemical substance is there.
So we tend to do these mms
and kind of lean in closer to things
that are attractive to us.
And when we see and experience things that we don’t like,
sometimes it’s a mild aversion.
We just kind of lean back or look away.
Other times, it’s an intense aversion of disgust
and we tend to cringe our face.
We tend to avoid inhaling any of the chemicals.
This probably has roots in ancient biological mechanisms
that are to prevent us from ingesting things
that are bad for us, chemical compounds
and tastes that might be poisonous.
So much of the foundation of any discussion about emotion
has to center around this kind of push-pull
of attraction to things or aversion from things.
Now, that’s a very basic way of thinking about emotions.
But if you think about it,
it works for a lot of different circumstances.
And in the brain,
everywhere from the deep circuits of the brain
to the more kind of what we call higher order
revolve centers of the brain,
we have this push-pull thing.
We’re either, in a previous episode, I talked about go,
the circuits that allow you to emphasize action
and then no-go circuits,
the circuits in the basal ganglia
that allow you to de-emphasize action and prevent action.
We talked about how that’s a push-pull.
So aversion and attraction is a push-pull too.
Delight or happiness or excitement
are attractions to certain things and ideas,
songs, people, places, foods.
Aversion is a leaning out.
It’s a disgust.
It’s an avoidance.
And so we can break down the discussion about emotions
into these simpler versions of themselves.
But at the core of that,
of attraction or aversion is an important theme
that you might realize already,
but most people tend to overlook,
which is that there’s an action there.
You’re either moving forward
or you’re moving away from something.
And anytime you’re talking about action
in the nervous system,
you’re talking about motor behaviors.
You’re talking about literally the contraction of muscles
to move you toward or away from things.
And anytime you’re talking about nerve to muscle and action,
you’re talking about the brain and the body
because the brain can’t move itself.
The brain has a body so that the organism can move.
And the body has a brain so that the organism, you,
can move toward or away from things
that you deem to be good or bad for you.
Now, some of these things that we’re attracted to
and some of them that we avoid
are what we call innate or hardwired.
You know, when we taste bitter compounds,
I’m not talking about bitter,
like you like a little bit of bitters in your drink
or something like that, but really bitter compounds,
we tend to avoid those
because they’re associated with poisons.
When we taste things that are sweet or that are savory,
we tend to pursue more of those.
We tend to lean toward those, so to speak.
And we tend to not avoid them.
So there are circuits in the brain for aversion
and for attraction toward things,
and the body is governing a lot of that.
And so immediately in this conversation,
I want to raise an important point,
which is about a nerve pathway
that many, many people have heard of
that gets discussed all the time
and that is one of the most kind of oversold
for the wrong reasons and undersold, unfortunately,
for its real power, which is the vagus nerve.
So the vagus nerve is one, not the only,
but one way in which our brain and body are connected
and regulates our emotional states.
Now, many of you have probably heard
about polyvagal theory.
I’m going to talk about this today.
Polyvagal theory was popularized by Stephen Porges.
And it’s an interesting theory.
Certain aspects of it, frankly, hold up to the science.
Some of it doesn’t.
And I’m going to discuss all of that today.
A lot of the vagus and the excitement about the vagus,
V-A-G-U-S, is because it somehow got into the mind
of the public that the vagus is involved
in calming us down.
So what is the vagus nerve?
Okay, we’re going to make this really simple.
In particular, for those that are just listening,
you can just imagine this.
For those of you that are watching,
I’ll point to the various areas.
But basically, vagus is the 10th cranial nerve,
which basically means that the neurons,
the control center of each of those neurons in the vagus,
lives just kind of near the neck, right?
And a branch of the vagus goes into the brain.
They send a little wire into the brain.
The other branch goes into the periphery,
but not just the gut.
It goes into the stomach, the intestines, the heart,
the lungs, and the immune system.
So this vagus nerve is incredible
because it’s taking information from the body,
and it has two directions.
The first is what we call sensory.
So it’s sensing things that are happening
in the gut, in the lungs.
Everything, for example, in the lungs,
when our lungs are distended,
the vagus nerve senses that
and sends that information up into the brain.
It also can sense things in the gut,
like how distended or empty your stomach happens to be.
It can sense heart rate.
It can sense your immune system,
whether or not you have bacteria
or things invading you in your body.
So it sends that information up to the brain.
So it’s a two-way street,
and sensory information is going up to the brain.
That’s all vagus.
So it’s like a superhighway.
Sensory information going one way,
and then the other direction is motor control.
So the vagus is not just for sensing things.
It’s actually for controlling things.
It’s got a sensory pathway and a motor pathway.
So that’s the first thing I think everyone should know
about the vagus.
In fact, it’s so important
that I feel like this is as important
as people knowing that walking involves flexors
And if you don’t think that’s important,
it’s as important as walking, frankly,
because the vagus is the way in which you can govern
the brain-body connection
and in which you can steer various aspects
of your mood and wellbeing.
But most people just don’t understand how to use it.
So first you got to understand what it is.
So you’ve got sensory information
coming from all these different organs of the body
up to the brain.
You got motor information going from the brain
back to the body.
And so you’ve got this superhighway within you.
Now, what actually regulates the vagus?
Oftentimes you’ll hear things like,
oh, you know, this particular behavior,
you know, rubbing your face at a particular location
or breathing in a particular way,
or, you know, a warm bath or something
stimulates the vagus.
Well, right now I want everyone to know that,
quote unquote, stimulating the vagus, broadly speaking,
is a terrible way to think about the vagus.
Because did you know what?
If you have a contaminant inside your body,
the vagus senses that and projects that information
to your brain and you start to generate a fever.
You start to try and kill that contaminant in your body.
So I don’t know that you want to stimulate the vagus
just as like a general theme.
Today, we’re going to get specific
about how you can activate particular circuits,
certain pathways from certain organs to the brain
in order to feel better or relieve certain conditions.
But you certainly don’t want to just stimulate the vagus.
Now, excitement about the vagus in part
is because of what quite honestly
was a fairly pioneering theory about the vagus,
which is this polyvagal theory.
So polyvagal, the word poly means many,
is cool because it acknowledges
that the vagus has a lot of different branches.
It’s not just one thing.
And so I really like that.
I like the naming polyvagal.
The idea that Porras put forward
was that there’s a dorsal vagus,
which is kind of runs the back of the spinal cord,
which is involved in alertness and activation
and kind of fight or flight type stuff.
And that there’s a ventral pathway.
And that that’s involved in more kind of empathic behaviors.
That is not quite in agreement with the modern anatomy,
but he was doing the best with what he had at the time.
The problem I have with the polyvagal theory
is the way that it’s discussed.
People often say, oh, you know,
if your dorsal vagus is too active,
then you tend to be someone who’s a little too keyed up.
And people who are kind of in a state of freeze
or kind of flaccid and kind of, you know,
just not really active and they’re just lethargic.
Well, then that pathway is hypoactive.
It should be more active.
So, there are a lot of theories
about how psychology maps onto the vagus
that as far as I know, don’t map to any real physiology.
Now, the other problem with this kind of
the way that the polyvagal theory is discussed,
probably not by the real experts,
but by a lot of people is that people start to diagnose
different psychological and physical manifestations
through the vagus.
They would say things like, oh, you know,
this person is hyperflexible at the joints
and therefore their dorsal vagus isn’t active enough
or something like that.
And it’s really kind of gone way outside the lane lines.
So, today we’re going to clean up a lot of that.
Let’s make it really simple
about how the vagus actually works,
at least as we understand it today in 2021.
First of all, as I mentioned, you have sensory information.
The same way that you detect light with your eyes
or you hear sounds with your ears,
you have sensors in your gut
that sense how full or empty your gut is.
It can also sense how acidic your gut is.
It can sense various things within your gut.
Your heart is doing the same.
It’s informing the brain how fast your heart is beating,
how full your lungs are has been communicated,
and then the status of your immune system.
So, the way to think about the vagus
is the same way I would think about the eyes.
The eyes are looking at colors, they’re looking at motion,
they’re looking how bright it is.
And each one of those things, those features,
is telling the brain something different
so the brain can decide when to be awake or asleep,
whether or not it’s looking at somebody
attractive or unattractive.
The vagus nerve is also analyzing many features
within the body and informing the brain
of how to feel about that and what to do.
So, a really good example that I think is an exciting one
is as it relates to sugar.
So, we all know that sweet things generally taste good.
I’m not particularly a fan of very sweet things.
You know, I’d much rather have, you know,
cheese or pizza or hamburger or steak.
I like savory fatty foods, but I do like sweet foods.
And most people find sweet foods to be attractive.
They want them.
They might or they might not be able to regulate
their behavior around them, but they want them.
And what’s really interesting is that for hundreds of years,
people have thought that that’s because of the way
that sweet foods taste.
So, that makes sense, right?
You eat something, it tastes sweet.
You want more of it.
Well, it turns out that it’s much more interesting
When you eat something sweet, within your stomach,
you have cells, neurons, that sense the presence
of sugary foods independent of their taste
and signal to the brain.
So, those sensors, those neurons send information
up the vagus to your brain,
goes through a series of stations,
and then you release dopamine.
This molecule that makes you want more of whatever it is
that you just ingested.
In fact, this pathway is so powerful
that they’ve done experiments where they completely numb
all the taste and feeling in somebody’s mouth.
They’re blindfolded, so they don’t know what they’re eating.
And they’re eating a food that’s either sugary
or not sugary.
And what they find is that even though people can’t taste
the sugary food, they crave more of the food
that contains sugar because of the sensors in the gut
that sense sugar.
So, to put this differently,
you actually have sensors within your body
that make you crave sugar independent
of the sweet taste of those things.
Now, that’s incredible.
And what it does, and what it tells us,
is that we have circuits in our body
that are driving us towards certain behaviors
and making us feel good, even though we can’t perceive them.
Now, for those of you that are really interested
in gut intuition and kind of gut feelings,
this is a gut feeling,
except this is a chemical gut feeling.
This is a particular set of neurons
detecting that something in your body
has a particular feature, in this case,
the presence of sugars, and sending information
to the brain essentially to control your behavior.
And I find this remarkable because what it means
is that what we call attractive isn’t always coming
from our thoughts about that,
or our feelings, or even our perception.
We are drawn to particular foods,
and we’re drawn perhaps also to particular people,
places, and other things because of information
that’s coming from our body.
And we’re going to talk about
what one can do with this information.
I know many people are thoughtful
or concerned about sugars these days,
thinking, you know, we all ingest too much sugar.
There’s sugar snuck into all the things we eat.
And indeed, that’s true.
I mean, this should completely reframe
the way that we think about
the sort of so-called hidden sugars in foods.
What this means is that even if a food is very savory,
like a piece of pizza, or a piece of bread,
or even like a salad dressing,
if there’s sugar snuck into that and you can’t taste it,
you will still crave more of that thing
without knowing that you crave it because it has sugar.
In other words, you might find yourself
wanting certain foods
and not knowing why you want those foods.
So I find this to be a fascinating aspect
of our biology.
And yes, it relates to mood and emotion.
And we’ll talk about how that is in a moment.
So let’s just back up a bit and ask the question,
why do we eat certain things?
And why do certain foods make us feel good
and other foods actually make us feel anxious?
I think some people may be familiar with this.
Other people might not.
But most people don’t realize that as you approach eating,
there’s an anxiety associated with that.
It’s an alertness.
Remember in the previous discussions,
or even if you don’t and you haven’t seen those,
all of your moods and feelings of wellbeing
are anchored on this continuum of alertness versus calmness.
And we hear so often about rest and digest,
that, oh, after we eat, we feel really nice and full,
hopefully comfortably full and not too full.
And we’re relaxing and we feel satiated.
It’s associated with serotonin, this molecule of satiation.
That’s all true.
But what most people don’t know
is that there’s an area of the hypothalamus,
so deep in the brain,
kind of in the middle deep portion of the brain,
called the lateral hypothalamus.
And the lateral hypothalamus is really interesting
because it controls feeding, but it inhibits feeding it.
It stops us from feeding.
And there’s another area in the brain.
If you want names, I’ll give them to you.
If you don’t want names, just ignore them,
delete them from your memory and awareness,
called the locus coeruleus.
Now the locus coeruleus sits back further in the brainstem
and it releases norepinephrine,
which is essentially adrenaline and makes us feel alert.
Now locus coeruleus has a lot of different functions
in the brain, but when we are going to eat,
let’s say we walk into a restaurant,
we sit down or we’re preparing a meal,
locus coeruleus is known to release noradrenaline
in the brain.
It’s creating a kind of alertness.
This has ancient utility, but it’s creating this alertness.
And for many people, they experience that
as they approach food, as stress, as anxiety.
But what’s interesting is that as we approach food,
locus coeruleus is releasing all these molecules
that make us feel more anxious and alert.
Sometimes it’s felt as excitement,
and that has probably to do
with how we feel about food generally.
Are we happy with our relationship to food?
Are we trying to restrict our relationship to food?
Are people coming over for dinner?
All that will play in, of course,
but there’s a certain stress and anxiety
on approach to food.
And as we approach food and we feel that anxiety,
locus coeruleus activates the lateral hypothalamus
in a way that inhibits feeding,
that makes us not want to eat.
So a lot of people who have kind of pre-meal anxiety
or anxiety around food,
and they can’t seem to just calm down and have a good meal
to access that later rest and digest,
a lot of that is because of this heightened stress
upon approach to food.
And a lot of the tools that are out there,
both for eating disorders
and for just kind of the general public
who isn’t suffering from eating disorders,
things like mindfulness around meals.
They always tell you,
you should never eat when stressed.
I’m sorry, but my life is not organized
in a way that I can’t do that.
I would never eat, right?
Because I eat when I’m awake,
and I don’t know if I’m stressed,
but I don’t think I am,
but I tend to run around a lot during the day.
I don’t generally take time
to do two or three deep breaths before I eat.
I generally will just keep, will eat.
That can be healthy or unhealthy
depending on the quality of your digestion.
I think using digestion as a guide is good,
but a lot of people aren’t aware
that this interaction between locus coeruleus
and lateral hypothalamus is a basic mechanism
where we are supposed to get a little bit alert
and anxious around mealtime.
And then as we eat,
the mechanisms for calming and satiation
are supposed to kick in.
And those mechanisms involve,
as I mentioned earlier, two things.
One is how things taste.
Digestion starts in the mouth, of course.
We taste our food.
Everyone tells us we should chew our food more.
Yes, that can improve digestion.
We’re not supposed to drink too many fluids as we eat.
That’s true too.
But a lot of how we feel while we eat
and after we eat is because of this vagus sensing
of what’s in our gut.
It’s sending information all the time.
Is there sugar?
Are there fats?
Are there contaminants?
There are a lot of information,
these so-called parallel pathways
that are going up into our brain
that regulate whether or not
we want to eat more of something or not.
And there are accelerators,
things that make us want to eat more,
like sugar and fats,
because those are nutrient dense
and they helps generally, at least in the short term,
support the survival of animals,
but also amino acids.
And this is very important.
There are a lot of data,
but much of what comes from the data
on what people eat and how much they eat
is from a subconscious detection
of how many amino acids and what the array,
meaning the constellation of amino acids is in a given food.
And it’s fair to say that the sum total of these studies
point in a direction where people will basically eat,
not until their stomach is full,
but until the brain perceives
that they have adequate intake of amino acids.
Now, this is a conversation that comes up
in the context of the meat only, the keto,
the kind of zone diet, the Mediterranean diet,
the vegan diet.
I’m largely going to ignore the kind of strict camps today.
I will talk a little bit about it
because I think each one of them
actually taps into something important
about this brain body relationship
that the other ones don’t.
But I don’t want to get into a discussion
about the ethics of different foods
of animal-based or non-animal-based
because that’s not the topic today.
It’s really about nutrient sensing and amino acid sensing.
So we generally will eat until our gut tells our brain
that we have adequate amounts of these amino acids.
Amino acids, of course, are important
because they are the building blocks of, sure,
muscle and the other things in our body that need repair.
But what most people don’t realize
is that amino acids are what the neurochemicals
in the brain are made from.
Now, this is vitally important, okay?
So we’ve heard dopamine is this molecule
that makes you feel good.
Actually, dopamine is a molecule that makes you feel good.
It’s released within the brain
and it does feel very good when you have dopamine release.
Dopamine release is caused by surprise, excitement,
events that you’re looking forward to
and that turn out well.
It is inhibited by events you’re looking forward to,
that don’t work out.
When someone says they’re going to call
that you’re really, really excited to talk to
and then they don’t.
Or you thought a movie was going to be really great
and it’s not.
Or you expect a meal to be really delicious
and it’s kind of eh.
And we actually, there’s a name for that.
It’s called reward prediction error.
So if, and you can actually use this
in the context of meals and plans
in a way that’s very useful with yourself
and people you know.
Essentially, if you expect something to be really terrific,
it really does place a higher expectation
at the chemical level.
So if you don’t get as much dopamine
as you’re expecting from something,
so you hear about a really great restaurant
or a place that has a really,
in my case, I wouldn’t call it an addiction.
I would call it more of an affliction for croissants.
The best vegetable, of course, is the croissant.
And I get really excited about the fact
that someone will tell me, oh, there’s this place
and they have incredible croissants.
You got to go there.
So I get really excited and I’ll go.
And just them telling me
that it’s going to be really terrific raises an expectation,
a dopamine expectation.
And unless those croissants are amazing,
chances are I’m going to experience them as less good,
I will truly release less dopamine
than I would had they just said,
oh yeah, I think that there are croissants down the street
or if I just tried one at random.
And that’s because of this reward prediction error.
Your expectation of something releases dopamine
and the actual event releases dopamine.
And if the event related dopamine
does not exceed the expectation or at least match it,
there’s a much higher tendency
that you won’t pursue that thing again.
So dopamine is really powerful
and it’s not just the molecule of reward,
it is the molecule of desire.
It’s the molecule of wanting,
not just the molecule of having.
And a book, since people often ask for book recommendations,
I don’t know the author personally, but I love the book.
It’s called The Molecule of More.
It’s a terrific book.
I wish I had written it, frankly.
But if you want to learn more about dopamine,
reward prediction error,
and how dopamine regulates various aspects
of your emotional and motivational life,
it’s a terrific read.
Dopamine is what’s going to lead us
to want to eat more of something
or to not want more of something.
Because dopamine really is about craving.
It’s about motivation and it’s about desire.
And as I mentioned, these amino acid sensors in our gut
are detecting how many amino acids,
but they’re also detecting which amino acids.
And there’s a particular amino acid called L-tyrosine,
which comes from food.
You can look up online which foods contain L-tyrosine.
It is in meats, it is in nuts,
it is also in some plant-based foods.
L-tyrosine is the precursor to a couple other molecules
like L-DOPA, et cetera, that make dopamine.
And so there’s a misconception out there
that most of the serotonin is in our gut
and most of the dopamine is in our gut
and therefore our mood is in our gut.
That’s not quite the way it works, okay?
We’ll talk about serotonin in a moment,
but dopamine is synthesized
from the amino acids that you eat.
However, the dopamine neurons that give rise
to these feelings of good or wanting more
or desire and motivation, those reside in the brain.
So we don’t want to get too confused.
We want to respect and honor the power of the gut
and this vagal pathway,
but it’s really neurons within your brain
that drive the pursuit and decision-making.
So what does this mean?
Well, some people make too little dopamine.
Some people make so little dopamine
that they need prescription dopamine.
They need L-DOPA.
People with Parkinson’s take L-DOPA
and other compounds to increase dopamine
because Parkinson’s is associated
with deficits in movement.
It starts as a tremor.
Actually starts as some other things that are interesting.
We’ll talk about in a moment,
but Parkinson’s is a depression.
It’s a blunting of motivation and mood and affect
and it’s a tremor.
And then eventually in severe conditions,
it’s challenges in speaking and walking.
So some famous examples would be Muhammad Ali,
Michael J. Fox, the great boxing trainer, Freddie Roach.
These people have Parkinson’s
and they, at least later in their life,
had challenges speaking.
Now, it’s not just fighters that develop Parkinson’s.
As far as I know, Michael J. Fox wasn’t a fighter.
People can develop Parkinson’s
and Parkinson’s is a depletion
of dopamine neurons in the brain.
And it’s not just movement challenges,
it’s challenges with mood.
Now, hopefully most of you, all of you,
don’t have Parkinson’s,
but it’s clear that dietary L-tyrosine
supports the healthy production of things like dopamine
and as well as other factors within the brain.
Now, some people immediately ask,
well, should I supplement L-tyrosine?
So let’s just talk about that
because that’s going to come up.
Full disclosure, I sometimes take L-tyrosine.
I’m not taking it right now, but I take it only occasionally.
You can buy this in capsule form.
It does increase kind of mood and elevation and alertness.
It is over the counter.
You have to check with your doctor.
I’m not responsible for your healthcare
and I’m not a doctor.
Whether or not it’s safe for you.
People with preexisting hyper-dopaminergic conditions
like mania should probably not take L-tyrosine.
The other thing about taking L-tyrosine
is there is a crash, okay?
It’s not a massive crash if you take it at appropriate doses
and it’s right for you,
but it can produce a crash and a lethargy
and a kind of brain fog after the next day or so.
And so L-tyrosine, however,
can be ingested through foods or through supplementation
to increase dopamine levels.
Taking chronically, however,
it can disrupt those dopamine pathways.
Now, there are other drugs that will increase L-tyrosine
and dopamine as well,
but those are severe enough
that they generally tend to have addictive properties.
So things like methamphetamine,
things like cocaine are terrible
because they really ramp up the dopamine system so much
that people really can’t achieve dopamine release
through any other mechanisms.
But food and the ingestion of L-tyrosine
has a profound effect on our levels of dopamine.
It takes a little while,
but that really will impact level of mood.
Certain antidepressants fall into the category
of dopaminergic antidepressants.
One of the most famous ones, of course, is Welbutrin.
Welbutrin was developed
because a lot of the other antidepressants
tend to make people feel kind of lethargic
or they had side effect profiles that people didn’t like.
So they developed this thing
that the generic name is different,
but it’s generally called Welbutrin.
Welbutrin activates dopamine and epinephrine,
which is a substrate of dopamine,
and both of those are involved in motivation
and alertness and effort.
So you might say, wow, this sounds like a great drug.
However, this drug, the side effect profile
tends to be the things that are associated
with elevated mood and alertness.
So this isn’t like taking some L-tyrosine,
this isn’t like eating some tyrosine-rich foods.
This is really a much greater release
of dopamine and epinephrine,
and it increases things like anxiety,
sweating, the pupils dilate.
It has certain effects on,
in particular, people with epilepsy.
It’s been used somewhat successfully for smoking cessation,
but again, it’s not for everybody,
and I’m not here to encourage the use of these things.
I’m just describing the biology and the rationale
for why these drugs were developed.
So let’s back up a second.
Let’s just kind of take stock of where we’re at.
We have a brain-body connection.
There are many of them,
but one of the main ones is the vagus nerve.
The vagus collects information about a lot of things,
breathing, heart rate,
stuff that’s happening in the gut, et cetera,
and gut, by the way, includes the stomach and the intestines,
sends that information up to the brain.
The brain is using that information
to decide one of two things,
move toward something or move away.
It can also pause,
but essentially pausing is not moving toward.
So that’s the dopamine pathway,
and foods rich in L-tyrosine
generally give us an elevated mood
and make us want to do more of whatever it is
that we happen to be doing, as well as other things.
Motivation generalizes to other things.
It’s not unique to just ingesting foods,
but foods that give us a big pulse of dopamine
will make us crave more of that food.
It will make us crave more of the activity
that led to the ingestion of that food.
And as I mentioned earlier,
a lot of that is happening at a subconscious level
that you’re not even aware of.
And this is why I think the concern about hidden sugars
and over-ingestion of sugars is serious
because it’s not just that the sugars
are impacting our blood glucose in negative ways,
although often it is,
it’s not just the obesity crisis that’s happening,
it’s also the fact that it’s disrupting our dopamine systems.
Now, that doesn’t mean all sugar is bad.
Some people have a quite healthy relationship to sugar,
but I think most people are just not aware
that sugar isn’t just operating at the level of taste,
it’s operating at the level of neurochemicals
and it’s doing it subconsciously.
So I’d like to talk about some of the other pathways
between brain and body
that regulate our moods and emotions,
but also are actionable.
So the other neuromodulator that’s really interesting
in the context of the vagus is serotonin.
Serotonin, just to remind you, is a neuromodulator,
therefore it creates a bias in which neural circuits,
which neurons in the brain and body are going to be active,
and it makes it less likely
that other ones are going to be active.
I think it’s fair to say without ever having measured it
that my bulldog Costello must just,
his brain and body must be swimming in serotonin
because he’s very calm and he eats a lot,
but he generally feels pretty sated.
He’s kind of an animal that’s obsessed with comforts.
He’s a bit of a hedonist.
And serotonin, when it’s elevated,
tends to make us feel really comfortable
and kind of blissed out wherever we are.
And that contrast with dopamine and epinephrine,
which mainly put us in pursuit of things,
motivation is pursuit.
Serotonin is more about feeling really comfy where we are.
The conversation around the brain-body relationship
and mood in serotonin for many years was,
well, you eat a big meal, the gut is distended,
you’ve got all the nutrients you need,
you rest and digest, and serotonin is released.
That’s sort of true, but there’s a lot more going on
and a lot more that’s interesting
and actionable that’s going on.
First of all, some of you, but perhaps not all,
have heard that more than 90% of the serotonin
that we make is in our gut.
And indeed, we have a lot of serotonin in our gut.
We have neurons in our gut that make serotonin.
We have neurons in our brain that make serotonin.
But here’s the deal.
Most of the serotonin that impacts our mood
and our mental state is not in our gut.
Most of it is in the neurons of the brain
in an area called the raphe nucleus of the brain.
There are a few other locations too.
And those are the neurons that control
whether or not we feel satiated or not,
whether or not we feel happy and calm.
You can’t have a discussion about serotonin
without having a discussion about antidepressants
because during the late 80s and early 90s,
there was this explosion in the number of prescription drugs
that were released,
things like first one and most famous one is Prozac,
Zoloft, Paxil, a number of other ones
that are so-called SSRI,
selective serotonin reuptake inhibitors.
That’s a long acronym,
but basically those drugs work by preventing
the gobbling up of serotonin
or reuptake of serotonin into neurons
after it’s been released,
which leads to more serotonin overall,
which means to elevate serotonin.
And indeed those drugs were and can be very useful
for certain people to feel better in cases of depression
and some other clinical disorders as well.
So I really don’t want to dismiss them
as useless or dangerous for everybody.
They can be quite useful for many people.
Not everyone responds well to them,
as I’m sure you’ve all heard,
and their side effect profile
has effects like blunting affect.
It can make people feel kind of flat, kind of meh.
It can reduce appetite for food.
It can reduce appetite for sex.
It can do all sorts of things,
or it can work really well.
Sometimes it’s a dose-related issue, et cetera.
Serotonin is fascinating, however,
because how well those neurons in the raphe work
is impacted by some events within the gut.
Although you might be surprised to find out
what those events are.
So let’s go a little bit deeper into the gut.
And again, the gut includes the stomach
and then the small intestine and the large intestine.
And ask like, what is going on with serotonin in the gut?
How is it impacting serotonin in the brain?
And let’s think about this in the context
of how some of us might want to increase
or decrease our serotonin levels.
So as far as I know,
there aren’t any really good at-home blood tests
for things like serotonin and dopamine.
There are some commercial products out there,
but to me, just to me, I’m not particularly impressed.
You know, it’s not the same
as getting your hormones levels measured
or your metabolic factors measured.
That can be done and can be done rigorously.
There are tests out there.
There are even some, believe it or not,
there’s some questionnaires, you know,
and I think actually last year
it made some of the bigger newspapers.
You know, are you more of a dopamine or a serotonin?
Are you a this or a that?
I find that stuff to be a little silly,
although I do appreciate and like the fact
that people are thinking about
and talking about neuromodulators.
There aren’t really great ways
to measure these things outside the clinic.
There’s some great clinical tools
that you can get inside of a hospital
or from a proper endocrinologist or neurologist,
but no great at-home tools.
So maybe that’s a call to arms
for some of you entrepreneurial folks out there
to create these tests, accurate tests, please,
that could be done at home.
But you know, some people feel like they’re too anxious
or they’re always in a motivated state
and they’re trying to adjust their serotonin.
Many people adjust their serotonin by just eating more food
and carbohydrate-rich foods will increase serotonin.
I’ve talked about this on a previous podcast,
but I personally am a big fan, at least for me,
as I usually fast and exercise in the early part of the day.
I eat a relatively high protein and moderate fat,
zero carb or low carb meal at lunch
and in the afternoon to stay alert
because those foods tend to favor dopamine production,
epinephrine production, and alertness.
My mood is generally pretty good most of the time.
And then as evening comes around
and I’m concerned about sleep and a good night’s sleep,
not concerned in an anxious way,
but I want to get a good night’s sleep,
I will ingest foods that promote serotonin release
because they contain a lot of tryptophan.
So if I do eat meat,
it would be like a white meat turkey meat.
I don’t tend to, I’ve never liked turkey.
I don’t mind the animal, but I don’t like ingesting the meat.
But starchy carbohydrates will increase serotonin.
Some people also will take serotonin.
You can now buy 5-HTP supplements.
This is a little bit tricky.
5-HTP supplements can, of course, increase 5-HTP.
It is 5-HTP or serotonin,
but that sometimes can create problems
in endogenous or self-made production of serotonin.
So I’m never a fan of taking things
very close to the chemical you’re trying to increase
for very long periods of time, maybe for occasional use.
I have the problem that if I take serotonin supplements,
5-HTP, I fall asleep.
The sleep I have is very intense
and I wake up three or four hours later.
And we know based on sleep studies
with good measurements in the lab
that serotonin release tends to be
in the later part of the night.
And so by taking it early in the night,
it really can disrupt the pattern of sleep
and the depth of sleep.
Nonetheless, some people are interested in taking serotonin
to get some of the more blissed out effects.
You can achieve that with foods, as I mentioned,
that are carbohydrate rich.
So as you’re seeing,
this isn’t really a discussion about nutrition per se.
This is a discussion about food, which contains amino acids,
amino acids being the precursors to neuromodulators
and neuromodulators having a profound effect
on your overall state of alertness or calmness,
happiness, sadness, and wellbeing.
So there are a number of things that one can take,
as I mentioned, one of them being 5-HTP itself.
Now, I’m not recommending people take anything,
but if you’re interested in what this does
and you want to explore this,
of course, you’d want permission from your doctor.
You can go to this free website.
I love this resource.
They don’t pay me to say that, but I just love this resource.
I followed it for a long time, called examine.com.
Thank you folks at examine.com
for putting this free resource out on the web
that has links through what they call
the human effect matrix.
So it’s links to all the PubMed studies
for particular effects of particular compounds
that one can buy and ingest.
Incredible, as well as important health warnings.
So I’m not going to read through everything,
but if you were to go to examine.com, as I have now,
and you’d put in 5-HTP,
they’re only looking at things that have strong evidence.
PubMed articles, articles are in the PubMed archive.
So for instance, I didn’t know this,
but 5-HTP produces a notable decrease in appetite.
And this appetite suppression makes sense, of course,
because we ingest foods to get serotonin.
And if we have enough serotonin,
then there’s no reason to ingest more foods.
It tends to have a blunting of appetite.
It probably does that also through other mechanisms.
So I’m not saying you should do this,
but if someone’s trying to blunt their appetite,
could be a interesting route.
Although I don’t recommend chronic use.
Not surprisingly, there’s a decrease in body weight
as a consequence, an increase in cortisol.
So that’s kind of important to note
that when you typically in biology,
if you pull on one string really hard, another one moves.
It’s a little bit like a puppet
and there’s more than one string on the puppet.
So it does seem to increase cortisol,
though they report as a minor effect.
Again, links to all those studies are there,
which is why I’m not listing them out in our caption notes.
You can go and get them at examine.com,
put in serotonin and you’ll find that.
So I find it fascinating that nowadays there are things
that are somewhere between doing nothing,
getting serotonin from tryptophan in foods
and prescription drugs.
There’s this other category of supplements
that are really interesting
for modulating these chemicals in the body.
And I should mention before I move on,
because I mentioned L-tyrosine,
I neglected to mention earlier
in our discussion about dopamine.
If you’re interested in the dopamine pathway,
go to examine.com, put in mucuna prurens.
It’s M-U-C-U-N-A, separate word, P-R-U-R-I-E-N-S.
It is a velvet bean that grows from vines
and is very itchy to touch due to serotonin on its surface.
Amazing, this bean has serotonin on its surface.
And indeed serotonin, if you were to put it on your skin,
would cause some irritation of the skin, amazing.
Inside the bean is L-DOPA.
Mucuna prurens is not just something
that promotes dopamine release
because of some weird mystical ancient thing
or whatever, or sorcery.
It is chemically L-DOPA, the precursor to dopamine.
It contains some other molecules as well
and low levels of other psychoactives.
This stuff is available over the counter.
Incredible, I personally find it incredible.
Its effects are really interesting.
I’m not going to read them all off,
but I mentioned these effects
not because I’m encouraging you to take it,
but because you get a window into what dopamine,
acute dopamine increase does
in the non-Parkinsonian context.
And you can start to think about foods
that are rich in L-tyrosine
as biasing certain effects or not others.
So when you hear food is medicine,
food isn’t really medicine, food is food,
but food has these chemical effects as well.
So first one listed is three studies
with a very high rigor
that overall have a minor effect on,
of all things, sperm quality.
So it appears that sperm motility itself,
I’m assuming when they say sperm quality,
I don’t know what features of sperm of quality
they looked at with sperm.
That’s not a discussion I want to have,
but I’m assuming it’s motility
because I know enough about reproductive biology
to know that sperm’s ability to swim
depends on some proteins that are present
in the front of the sperm, et cetera,
things like pentraxins,
and sperm motility is generally associated
with sperm quality.
Sperm that don’t move are generally not very useful sperm.
Symptoms of Parkinson disease
are notably degraded with macune appearance.
So fascinating, that’s not surprising.
And there are a lot of other effects here.
Feelings of subjective wellbeing,
testosterone, reductions in prolactin, not surprising.
Prolactin is a hormone that’s involved in milk letdown.
In lactating mothers, it’s involved in feelings of peace
and generally is antagonistic to sexual desire
in both men and female.
So it’s really interesting that things like macune appearance
which are L-DOPA, reduced prolactin, increased sperm motility,
increased testosterone, subjective wellbeing.
So you’re starting to see a theme, right?
Dopamine really makes us motivated,
feel in pursuit, makes us feel good.
Serotonin makes us feel more relaxed and calm.
Now, this whole month is about emotion.
So you might be thinking, well, wait,
where are we going with all this as it relates to emotions?
But in the last episode,
I said something I’m going to repeat it now briefly,
which is that much of what we talk about
is good emotions or bad emotions.
There’s a context to that.
There’s a social context.
You can’t really say an emotion is good or bad.
Grieving at a funeral is healthy, okay?
Being happy at a funeral,
assuming you loved the person that died,
is most people probably wouldn’t think that was healthy.
So we can’t really say that certain emotions
like sadness or happiness are healthy.
It’s context is important.
Cultural context is important.
Many of you have asked for book recommendations.
This is an opportunity to raise a mention of another book.
Again, I don’t have any financial affiliation or anything,
but if you want to read more about emotions
and how the context and cultural things
impact our emotions, I’m a huge fan of Lisa Feldman Barrett.
I learned about her from the Lex Fridman podcast.
I’ve had discussions with her on my Instagram Live.
She’s at Northeastern University,
a world expert in emotions.
Her first book is, How Emotions Are Made.
This is not a book she sent me.
I paid for this with my own money years ago.
Bought it, read it, loved it long before I met Lisa.
I’m just delighted that we’ve got to known each other
a little bit.
It’s a really interesting read into the psychology
of emotions and some of the subjectivity of emotions.
So whereas I’m talking about mainly the biology of emotions,
this gets a little bit more into the psychology,
although the biology as well.
And Lisa’s just terrific.
She’s also putting a lot of information out into the world
So if you want to learn more about that,
check out her work.
Again, it’s Lisa Feldman Barrett,
and that book is How Emotions Are Made.
Hopefully she’ll continue to write many more books.
So now you understand the relationship, I hope,
between foods and dopamine, foods and serotonin,
and that they’re both being communicated to the brain
via the vagus, right?
We ingest these foods.
These supplements are things people take.
They don’t put them directly into the brain.
They put them in our gut.
So yes, there’s a gut-brain connection,
but it’s not about the serotonin in the gut
that makes you feel calm and placid.
It’s not about the dopamine in the gut.
It’s just been oversold that way
because I think there’s something really attractive,
and I understand about the idea that
because certain things about our experience of life
and our emotions is happening in our body
that maybe we have a little more control, right?
Because this thing is a hard container.
We can’t just stuff some dopamine in there.
I can’t just, you know,
I could probably take a mucuna prurines bean
and stuff it in my ear.
Please don’t do that.
It’d make my ear itchy
because of the serotonin on the outside,
but you can’t get stuff in there.
What you have to do is ingest things
that are metabolized in certain ways
that communicate to the brain,
or so maybe they pass into the brain themselves
across what’s called the blood-brain barrier.
I’m going to talk about the blood-brain barrier in a minute.
It’s actually called the BBB.
So it ends up sounding like baby, BBB.
I guess that’s like BB.
But there are also nerves in the gut
that are sensing the nutrient contents of food
and then saying, oh, you should feel better and want more.
Oh, that’s got a lot of bitterness and acid taste to it.
You should want less of that, okay?
So as I transition out of the discussion
about dopamine and serotonin in the gut,
hopefully you’ve got some actionable items
there under your belt, pun intended,
where you can understand how certain foods
and certain nutrients, and you can look these up,
might impact your mood.
If you’re somebody who’s really anxious and really wired,
well, then the dopamine-adrenaline pathway,
epinephrine pathway is probably not one
that you want to lean on any harder.
If you tend to be someone who’s pretty passive
and you’re having trouble with motivation,
well, then think about ramping up the dopamine pathway.
I always think behaviors and proper food choices
is the best way to start,
and behaviors include things like exercise, et cetera.
But one of the problems with the discussion
around mood and exercise or mood and meditation
is that it’s so subjective.
It’s like, I love certain forms of exercise and not others.
Certain ones are aversive to me.
Certain ones are attractive to me.
And it’s never really clear.
No one’s ever told me, okay, you have to do 10 minutes
on the bike at X number of RPM at so-and-so
or on the skier in order to get your dopamine up.
But we can actually say, if you ingest more L-tyrosine,
there’s a high probability
that you’re going to make more dopamine.
And I’m talking about ingesting it through food
or through supplementation, if you like.
Macuna purines, I’ve tried, I should just mention.
It was too dopaminergic for me.
I really, really jazzed up
and then severe crash for me the next day.
But that’s, I think, because I tend to ride pretty high
on the kind of alertness and motivation scale.
I’m always being told by Costello
and other people in the podcast studio
to slow my speech down.
This is me uncaffeinated.
And I could probably afford a little more serotonin
in my life.
So, whereas Costello, he could afford,
well, he could afford to wake up every couple days
and just say hello to us.
This dog sleeps more than any other creature.
So there are things that we can do and they’re actionable.
And they are, in some ways, they’re quantitative
because you can regulate dosages
and you can regulate amounts and you can regulate timing.
And everyone has to play with these things
and figure out what’s right for them in terms of feeding.
And everyone has to explore and understand
what’s safe and right for them.
But, and of course, exercise is still very important.
I talked about social connection in the last episode,
super important for activation of serotonin.
But when it comes to this gut-brain, body-brain relationship,
what we eat really matters
in terms of the neurochemicals that we make.
So let’s talk a little bit more
about things that we ingest in our body
and then allow our body to inform our brain
to shift our mood.
And this is something I’ve been doing for years.
And I just want to say,
I’ve found to be a complete game changer.
There’s excellent science to support it.
And I think most people are familiar with it
in a different context,
but I don’t think most people know this simple fact,
which is that the omega-3 to omega-6 fatty acid ratio
has a profound effect on depression.
It has a profound effect on mood.
So much so that in a double-blind placebo-controlled study
that I will provide the link to,
this was a study first published in 2008,
but there’ve been many others as well.
First of all, in an experiment done in animals,
they found there’s a model of learned helplessness
It’s not very kind to the animals,
but they put rats or mice in a jar,
they let them swim and they’ll swim, swim, swim
to try and save their life.
And eventually they give up.
It’s a learned helplessness.
They don’t let them drown, they take them out.
Adjusting the omega-3, omega-6 ratio
so that the omega-3s are higher
led to less learned helplessness,
meaning these animals would swim longer.
Okay, now that’s an animal, that’s a rat,
not a particularly kind study.
But that same study was essentially done in humans,
although they didn’t have them swim
to the point of near drowning.
What they did is they took people
who were clinically depressed, major depression.
Okay, major depression is severe maladaptive state,
meaning it inhibits job, relationships, appetite,
all sorts of negative health effects.
And they did a comparison of 1,000 milligrams a day of EPA.
So EPA is one of the elements
that contains high levels of omega-3s
that’s in things like fish oil.
I’ll talk about other sources in a little bit,
but it wasn’t 1,000 milligrams of fish oil,
it was 1,000 milligrams of EPA.
Compared that to 20 milligrams of fluoxetine,
which is Prozac, okay, really increases serotonin.
And in this study of 60 individuals,
again, I’ll provide the links to the study,
they found that they were equally effective
in reducing depressive symptoms.
So imagine that, a food-based compound
that you can’t make without, right?
This is not a situation
where you can make your own omega-3s,
you have to get them from food sources
or from supplementation,
was as effective as 20 milligrams of fluoxetine
over the course of eight weeks.
And what was really interesting in addition to that
is that the combination of 1,000 milligrams of EPA
and fluoxetine had a synergistic effect
in lowering depressive symptoms.
I find this remarkable.
I heard about this when it first came out
and I wasn’t sure what to make of it
because there are a lot of studies that come out
and I generally like to focus my changes in behavior
around things where there’s a large center of mass,
there’s a lot of information.
A couple of years later,
I did in fact start taking 1,000 milligrams per day of EPA
in fish oil.
Now, there are a few side effects of fish oil.
People who have blood, who are bleeders,
who have factor V Leiden mutations,
or women who are taking birth control,
which can affect blood clotting and things of that sort,
really should talk to your doctor,
make sure it’s okay for you.
Fish oil also can give people fishy breath,
which is pretty gross, frankly,
but there are now fish oils
that either because of the encapsulations
or because they put some lemon flavoring in there
doesn’t have that effect.
In any event, 1,000 milligrams per day of EPA,
I started ingesting that regularly.
I just felt better.
I wasn’t clinically depressed,
but I did feel, at least for me,
an increase in mood and affect
and a number of other things
that’s supposed to reduce inflammation.
The cardiovascular effects are controversial.
For a long time, everyone thought
the effects on platelets were really terrific.
Then there were articles that came out in major newspapers
saying maybe not so much,
but the effects on mood are really profound.
And now there are lots of studies.
If you go into PubMed and you were to put EPA
or fish oil and depression,
you would find that there were a number
of really impressive results
showing that it’s at least as effective
as certain SSRIs, antidepressants, at these dosages.
And it can amplify or improve the effect of low dosages
of some of these SSRIs.
So I feel like more people should know about this.
This is nutrition, but it’s profoundly affecting mood.
And depression is terrible, right?
Depression can have a component of anxiety in some cases
where people feel lousy and very uncertain.
That’s kind of how I talk about depression with anxiety
is you talk to someone who’s anxious
and you can tell them everything’s going to be okay, okay.
And they’re always concerned
about what they might not know.
You don’t really know the plane isn’t going to crash.
You don’t really know that life is going to go okay.
And in some sense, they’re right.
No one has a crystal ball or can predict the future,
but they tend to perseverate or fixate on the uncertainty.
And then of course there are the versions of depression
that involve certainty.
People are lethargic and they’re certain.
They say, yeah, I’m certain
I’m never going to get another job.
I’m certain I’m never going to meet anyone new.
I’m certain I’m going to fail.
So there’s this kind of a divide in the sphere of depression
around certainty and uncertainty.
But what’s interesting is this thousand milligrams per day
or more of EPA has been shown to relief
both forms of depression.
Now, does that mean it’s going to work for everybody?
No, I’m not here to try and play psychiatrist.
I want to point you in the direction of these manuscripts
so that you can make informed choices for yourself.
You can discuss it with your doctor and family
and make the choices that are right for you.
But here’s what’s especially interesting
about the heart effects,
because we’ve heard that these omega-3s,
which of course you can get from other sources too.
You can get from fatty fish.
There are flax seeds, hemp seeds.
There are a number of chia seeds, these kinds of things.
But the levels of EPA that are required are quite high.
So this thousand milligrams per day,
that’s pretty hard to get from food,
although it can be done depending on what you’re eating.
What’s interesting is that the heart effects
that are solid, that really stand up in the literature,
have a lot more to do with something we talked about
in a previous episode and I’ll mention again,
which is heart rate variability.
So we know that having a heart rate that’s really high
or a heart rate that’s really low,
neither of those are good.
A lot of people think,
oh, you just want a low heart rate, big stroke volume.
You know, if you’re running a lot,
you may have 30 or 40 beats per minute.
That’s great to be in shape,
but you still want heart rate variability.
It has a lot to do with the tone
of the autonomic nervous system.
I talked about last time how when you inhale,
it speeds up heart rate.
When you exhale, it decreases heart rate.
That’s called respiratory sinus arrhythmia.
It’s the basis of heart rate variability.
We’ll maybe do a short post about this
so you can get all the mechanism
and the behaviors that spill out of that
that might be useful for you.
But the point is heart rate variability, HRV is good.
And what’s interesting is that there was a study in 2009
that showed that people who eat a diet
and fail to supplement in a way
that there’s a high omega-6 to 3 ratio,
so not enough omega-3s,
not only are there markers
of inflammatory cytokines elevated,
things like IL-6 and TNF-alpha,
but they tend to be non-responders to antidepressants.
Shifting that omega-3, omega-6 ratio did a couple things.
First of all, increasing the amount of EPA,
shifted the ratio so it was higher omega-3
to omega-6 ratio, which was good,
lowered the inflammation markers,
and then allowed antidepressants to have their effect
even at low doses.
And here’s the really interesting thing.
It worked by increasing heart rate variability.
And you think, well, how in the world would this happen?
I mean, that’s a ton of effects,
but the way it works is because of the way
that these things are impacting the gut
and the autonomic nervous system.
Remember earlier I said the vagus includes connections
from the heart signaling about sensory information
about how fast the heart is beating to the brain,
not just stuff from the lungs,
but information from the heart,
and the brain then adjusts heart rate
by heart rate variability.
So it’s incredible that there’s a way
that one can use the gut,
the ingestion of more of these EPAs,
either through food or supplementation,
to increase heart rate variability,
and thereby to improve symptoms,
meaning reduce symptoms of depression,
and to even make low levels of antidepressants
that wouldn’t otherwise work, work.
And I think I like this study so much
because A, it’s super cool.
It bridges the brain-body axis.
It incorporates nutrition and micronutrients in the brain,
but also because it really points to something
that we hear all the time,
which is that our body is a whole system.
It’s working as a whole system,
and the brain isn’t working in isolation up there
in the skull.
It’s reacting to things that are happening in the body,
in the gut, and in the heart rate,
and heart rate variability,
and that the things we ingest
can have a profound effect on them.
Now, of course, I really want to emphasize something,
which is that no one compound,
or nutrient, or supplement, or drug,
or behavior for that matter,
is going to be the be-all, end-all
of shifting out of depression,
or improving one’s mood, or improving sleep.
It’s a constellation of things.
And this is especially true
when people start to get excited
about supplements and drugs of all kinds,
and their potential for various things.
Right now, there’s a lot of excitement about psychedelics
and their therapeutic uses, and I think, great.
But as a good friend of mine,
who’s a physician clinician says,
better living through chemistry
still requires better living.
You cannot expect to take a compound,
regardless of source or potency,
and have it completely shift your experience of life
without having to continue to engage
in the proper behaviors, all the things we know,
proper sleep, exercise, social connection, food, et cetera.
There are many others as well.
So I still find that this collection of studies
about omega-3 to omega-6 ratios to be profoundly important,
so much so that it’s completely changed
the way that I think about food, the foods I eat.
I do supplement.
I don’t necessarily think that’s for everybody,
but I really think it’s incredible
that there are these compounds
that have these robust effects on our feelings of wellbeing.
And there are others too.
So that 1,000 milligram per day threshold of fish oil
that’s beneficial requires that one take
a reasonable amount of these things,
either through food or through supplementation.
I acknowledge that not everyone wants to take fish oil.
There are a couple of reasons
why one might want to avoid that.
One would be for ethical reasons.
You have an emotional relationship
or a relationship to the environment
that makes you not want to ingest fish-related products.
There’s krill oil.
Krill is still an organism.
It’s a little tiny thing that whales eat a lot of,
and people generally eat very little of.
So krill is out there.
I personally, just me, I don’t know why,
I didn’t react well to krill.
It didn’t make me feel very good.
I had some like kind of skin itchies and things like that,
and they stopped when I stopped taking it.
But I don’t want to bias you against it
if that’s your preference.
Some people really like krill oil as a source of omega-3s.
I did mention some of the other sources
like chia seeds and flax seeds.
But as you’ll notice, these are not things
that we tend to ingest a lot of on a regular basis.
It is possible to get omega-3s from meats
if the animals have grazed on grasses
that contain a lot of omega-3s.
So for those of you that ingest meat,
the source of those meats is going to be very important
as it relates to omega-3s.
Even within the category of fish oil,
there’s a concern sometimes about mercury
and other contaminants.
You want to go with a brand that emphasizes
that they’ve gone to really good sources
and that they decontaminate regardless.
And so you have to search out those brands.
There is a test that you can do
as to whether or not the fish oil is rancid or not.
Some people take in liquid form.
Some people take in capsule form.
The liquid form is going to be more affordable.
The capsule form is a little easier and a little more
You can actually just chew one of the gel tablets.
And if it tastes really fishy and kind of rancid,
you’ll know it’s disgusting.
You’ll want to spit it out.
And if it doesn’t and it’s tolerable,
then you’ll know that it’s okay.
Unfortunately, you have to buy it first in order to do that.
Although, I don’t know,
maybe you can get them to open up the bottle for you
in the store and tell them that you don’t want to try it.
Someday, perhaps fish oil and omega-3s,
it’ll be like tasting wine in a restaurant
where you can send it back.
For now, I think you have to purchase it first,
but find a brand you trust and like,
and then work with them
if you decide to go that route, of course.
There are other compounds that are also interesting
for mood elevation that are essentially like foods
or are supplement-based that now, fortunately,
there are really good data from peer-reviewed studies.
And the next one I want to mention,
because I think it’s really interesting, is L-carnitine.
Now, L-carnitine has been around a long time
and it’s been discussed in the context of heart health
and a number of other things.
It was actually in tout as a bit of a weight loss agent
in the early 90s.
But L-carnitine actually has some really impressive effects
And again, we will look to PubMed
because looking at examine.com is essentially,
for me anyway, looking at PubMed, what is L-carnitine?
Okay, L-carnitine is most prevalent in meat
and in beef in particular.
Now, for the vegans, please know that L-carnitine
is available through non-meat sources as well,
although it’s not as enriched in non-meat sources.
It’s a really interesting molecule
because L-cetyl L-carnitine
is essentially what’s made from L-carnitine,
but it’s acetylated.
If you’re interested in the biochemistry,
you can look that up.
It’s acetylated into a form
that can cross the blood-brain barrier.
The blood-brain barrier or BBB is a barrier.
It’s a wall around the brain.
And you have this barrier because the brain is so important
and it has this feature that the neurons there
don’t recreate themselves after injury
like other organs of the body.
There’s not a lot of turnover of cells
despite what you might’ve heard.
And so nature has created this BBB,
this blood-brain barrier,
to make sure that certain molecules,
in particular large molecules,
don’t get across the blood-brain barrier
because it can be damaging to those tissues.
Incidentally, you also have a very rigid
or stringent barrier around other organs,
which are the gonads.
So the ovaries and the testes and the brain
are the organs of the body
that nature has gone out of its way to protect,
give this additional layer of the blood-brain barrier,
or as you might imagine for the testes and the ovaries,
it’s going to be the blood-gonadal barrier.
So these barriers exist and make it such
that just because you eat something,
just because you ingest it,
doesn’t mean it’s going to cross the blood-brain barrier.
But L-carnitine, when taken,
is acetylated and converted into this form
that gets across the blood-brain barrier.
And it has a lot of effects.
It’s involved in mitochondrial activation
of long-chain fatty acids, which that’s a big mouthful
that we could get into sometime
when we’re talking about metabolics,
but it has some interesting effects on the neuro side.
So if you decide to check it out on examine.com,
you’ll see some really interesting things,
lots of effects on ammonia, C-reactive proteins,
things of that sort, blood glucose is lowered, et cetera.
That’s all stuff that’s the level of blood in periphery,
slight effects in lowering cholesterol.
Here’s some interesting ones.
Rates of pregnancy go way up
when people are taking L-carnitine.
Both the father and the mother,
both the source of sperm and the source of egg
are affected in ways that favor pregnancy.
It does increase, here we go again,
with sperm quality, sperm motility in males.
And it seems to have positive effects on females
that have polycystic ovary syndrome.
So check that out.
The effects are very strong.
There are three studies listed there.
Again, I’m not promoting this,
but that people take L-carnitine,
especially if you’re trying to get pregnant,
but check it out because the effects there
and the studies that are mentioned
are published in peer-reviewed rigorous journals.
In terms of the neural effects, those are quite interesting.
The effects on depression are still emerging,
but they do seem to exist,
that people feel a notable decrease in depressive symptoms.
There are seven studies listed on examine.com
that it has a notable benefit in a variety of circumstances
where participants have heightened depression already.
They start taking L-carnitine and they start feeling better.
And they talk about dosages in those various studies.
It also has been shown to have a notable decrease
in the symptoms of autism, which I find fascinating.
Also, again, the things we ingest
impact the chemicals in our brain
and how they impact the rest of our body.
There’s other things that’s been used
to treat certain forms of alcohol dependence.
I think this is going to be a very exciting emerging area.
We’re going to do a whole month about addiction.
I’ve got a great guest lined up for that month,
but there’s now an emerging field
about what people can take and supplement
to help ease the cravings and the withdrawal
when trying to quit drugs of abuse like cocaine,
alcohol, heroin, and smoking and things of that sort.
So really interesting area.
This is, I like to think is early days
and we’re going to discover a lot more.
There’s a huge list of things here.
Since we talked about pain on a previous episode
and I know a lot of people have written to me
about fibromyalgia, L-carnitine has been shown
to reduce symptoms of fibromyalgia.
Again, all the links to studies are on examine.com,
totally free site.
And that was my bulldog being a battering ram.
There’s nothing graceful about this bulldog.
He’s decided he wanted to leave to go get a drink of water.
And so please forgive the noise.
Okay, so now let’s turn to another aspect
of the gut brain relationship that will surprise you,
in some cases might shock you,
and that has some really cool and actionable biology.
And that’s the gut microbiome, probiotics, and prebiotics.
I know today we’re talking about emotions and not pain,
but I’d be remiss if I didn’t mention another effect
of acetyl L-carnitine that’s been reported
and that you can find listed with link to study
on examine.com, which is its effect
in reducing the symptoms of migraine.
This was a randomized control trial
with 133 participants who had frequent migraines.
They were taking 500 milligrams of L-carnitine
or nothing for 12 weeks.
So the control is a little bit,
the control experiment there is a little bit tricky,
but it had a significant effect
on reducing the number of migraine attacks per month.
So I find that really interesting.
And there’s a lot more listed there about the study.
And I think these compounds are powerful.
They carry risks for certain people, not for others.
So again, you have to find out what’s right for you,
but I do think they are super interesting
as potential therapeutics for various people.
So what’s the deal with the gut microbiome
and the gut-brain axis?
Today, we’ve actually been talking a lot already
about the gut-brain axis
that has nothing to do with microbiomes.
We’ve been talking about this vagus nerve
that connects providing sensory information
from the body to the brain.
And then the brain also sends in the same nerve
motor information to control the motility,
the gut, the heart rate, how fast we breathe
and deployment of immune stuff,
killer cells and things of that sort.
But oftentimes when we hear
about the gut-brain axis these days,
it’s a discussion about the gut microbiome.
And once again, we’re in a situation
where there’s incredible biology.
I’m very happy there’s so much discussion
about the gut microbiome.
I am somewhat dismayed and concerned
that most of what I hear out there
is either false or partially false.
So we’re going to clear up some of the misconceptions
first by understanding the biology.
And then we’re going to talk about
some of the actionable items.
It is true that we have a lot
of these little microorganisms living in our gut.
They’re not there because they want to help us.
They don’t have brains.
They are adaptive, however,
they try and find and create environments
that make it easier for them to proliferate.
So they don’t care about you and me,
but they are perfectly willing to exploit you and me
in order to make more of themselves.
The same way viruses are.
Viruses don’t have a mind, they infect cells,
they hijack the genome
and they use that genome to make more of themselves.
The microbiota that live in us
vary along the length of our digestive tract.
But let’s just take a step back
and think about how our body plan is made.
We are actually a series of tubes.
Our brain is actually a tube.
You see, it’s all squishy on the outside.
And then it’s got that long thing,
the spinal cord that goes down to the base of the spine.
That’s the central nervous system.
That all started out as a tube.
It just looks like a cauliflower on the other end
up in the brain because the tube is so big
and it has to be crammed into the skull
so it gets all wrinkled up.
But if we were to splay it out,
you’d find that it’s just one big tube.
Similarly, our digestive tract and our airways
are essentially one big tube.
It starts with our mouth, also our nose.
And then we have all these other tubes
that go down through our throat and then into our stomach
and then into our various intestines.
And then the tube ends out the other end.
So we are one long tube for digestion.
And inside of that tube is a mucosal lining.
It’s these little microvilli, tiny, tiny, tiny,
little like velvety ends of cells
that are able to move and move things along.
And mucus, mucosa.
And the conditions of that mucosal lining
set a number of different things.
It sets the rate of our digestion
and the quality of our digestion.
It sets, for instance, our immune system.
Most people probably don’t realize this,
but most infections in the environment,
well, they have to get into our body somehow.
Some of them are inhaled.
A lot of them go into our mouth
and lodge in the mucosal lining of the mouth.
And then infections start there.
You probably had the experience, unfortunately,
of feeling like you have a tick in your throat,
like something’s irritating your throat.
And then it kind of migrates up into a head cold
or runny nose.
Sometimes it’ll start as a headache.
Sometimes it won’t.
But things that can migrate down into the gut.
So we’re ingesting things all the time.
Think about air, bacteria, viruses,
they’re making their way into our gut.
And some of those bacteria live in the gut.
And some of those bacteria
bias the mucosal lining in the gut,
stomach and intestines,
to be more acidic or more basic
so that they can make more of themselves,
so they can replicate.
They like a particular comfort.
It’s like they like a particular kind of bedding
to lie down in and create more of themselves.
Now, some of those mucosal linings that they promote
make us feel better.
They make us feel more alert.
They bolster our immune system
and others make us feel worse.
So first rule,
the microbiome isn’t good or bad.
Some of these little bugs that live in us
do bad things to us.
They make us feel worse.
They lower our immunity.
They affect us in negative ways.
Some of them make us feel better.
And they do that mainly by changing the conditions
of our gut environment.
In addition to that,
they do impact the neurotransmitters
and the neurons that live in the gut
and that signal up to the brain
to impact things like dopamine and serotonin
that we’ve been talking about previously.
So there’s a vast world now
devoted to trying to understand what sources of food,
what kinds of foods are good or not good
for the gut microbiome.
So let’s just talk about some general rules of thumb
related to the research,
quality research that’s peer reviewed.
And then in a future episode,
we will go far deeper into the gut microbiome
and gut brain axis.
But here’s a few things
that I think you might find surprising.
First of all,
supporting a healthy gut microbiome is good for mood,
great for digestion and great for immune system function.
However, that does not mean maxing out
or taking the most probiotic and prebiotic
that you can possibly manage.
As I mentioned many times before,
I do believe in probiotics, I take probiotics,
but there are studies that show
that if you take lots and lots of certain probiotics
like lactobacillus and you really ramp up the levels more,
it is not a case of more is better.
There are things like brain fog that can come from that.
Brain fog is just this inability to focus.
People feel really not well generally.
Some of those studies are a little bit controversial,
but I think it’s fair to say
that if people really increase the amount of probiotic
that they’re taking beyond a certain amount,
then they start feeling foggy in the mind.
Now, what’s too much?
Well, I get probiotics from,
I’ve mentioned before, from athletic greens.
You can get them from fermented foods like sauerkraut,
pickles, kimchi, natto.
These are different sources from around the world.
Actually, I’d love to hear some of the other sources
that people know, other foods from around the world.
I’m fascinated by the way in which different cultures
have all arrived at these foods that provide
and support healthy microbiomes because they’re fermented.
I have a colleague at Stanford, Justin Sonnenberg.
He and I have talked about this.
I don’t want to quote him inappropriately,
but we’ve had discussions about it
and they’ve published that the ingestion of fermented foods
is one of the best ways to support healthy levels
of gut microbiota without exceeding the threshold
that would cause things like brain fog.
So foods and fermented foods are going to be the best source
and there are a number of different ways
that one could do that.
Some people don’t like fermented foods, however.
Some people supplement it.
So it isn’t a case of more is better.
Okay, so we know that.
The other is that it is true that healthy gut microbiota
have been shown to improve symptoms
of certain psychiatric illnesses,
as well as certain conditions like particular features
along the autism spectrum, which is interesting.
And those effects are probably due
to not just improvement of immune system function,
but to the conditions in which the neurons
that sense nutrients convey information to the brain
and increased levels of serotonin and or dopamine.
So gut microbiome provides kind of a foundation
for healthy gut and healthy gut brain access.
So much so that some people report
that when they start eating small bits,
because it doesn’t require a lot of fermented foods,
that their overall mood is better.
Not unlike the effects of EPA,
although I don’t think it’s been looked at directly
in the context of clinical depression yet.
And if someone knows of a study,
please mention it in the comments.
That would be terrific.
There are some things that you can do
to really damage your gut microbiome.
And this is where there’s a huge misconception
that I want to clear up.
There was a study that was published in Nature,
which is among the three top journals
that we have in science.
You know, Nature, Science, and Cell
are considered the top tops,
but excellent journal that showed
that artificial sweeteners,
but a particular artificial sweetener, which was saccharin,
can disrupt the gut microbiome
in ways that is detrimental
to a number of different health markers,
increasing inflammatory cytokines
and all the other bad things that happen
when the gut microbiome is thrown off kilter.
That study was widely discussed,
but there were a few things that were not mentioned there
that are really important.
That study was about saccharin in particular.
Saccharin is not the most typical
artificial sweetener that’s used.
The most typical artificial sweeteners that are used
are things like aspartame, so-called NutraSweet,
or sucralose, or these days stevia.
There’s monk fruits.
To my knowledge, and please correct me
if anyone knows of any studies.
To my knowledge, the negative effects
of these artificial sweeteners on the gut microbiome
were restricted to saccharin.
Now, there is enough chemical similarity between saccharin
and some of the other ones that I mentioned,
but not all of them.
For instance, stevia, monk fruit,
are distinct in their chemical makeup
so that they probably don’t have,
if they have any, have lower effects,
negative effects on the gut microbiome,
but it should still be tested.
So saccharin is really,
it was shown in this study and several other studies,
can really negatively impact, excuse me,
the quality of the gut microbiome.
Interestingly, the narrative around artificial sweeteners
and gut microbiome is incorrect.
Most people thought, oh, saccharin is bad for the microbiome.
It must kill the microbiome.
And so you hear people saying, oh, you know,
artificial sweeteners kill the microbiome.
That’s not true at all.
In fact, in that very same study published in Nature,
they showed that the negative effects of saccharin
on the microbiome could be blocked or eliminated
by giving antibiotics.
So what happens is certain artificial sweeteners,
in particular saccharin, disrupt the microbiome
and make the environment within the gut,
that mucosal lining, more favorable to bacteria microbiota
that are not good for the organism, okay?
This is an important distinction.
It’s not just that a language thing where people say,
oh, you know, it kills the microbiome.
It doesn’t kill the microbiome.
It shifts the microbiome.
And shifts in the microbiome can be good
or they can be bad.
And that takes us to another topic.
That’s a bit of a hot button topic,
but I’m willing to go there
because I think it deserves conversation,
which is nowadays there are many examples out there
where people have switched from a kind of standard diet
or even a vegetarian diet or vegan diet to a keto diet.
Now, keto doesn’t necessarily have to mean
the ingestion of meats, but it can.
And they experience positive effects for themselves.
Not everybody, and I’ve talked previously
about some of the kind of the incorrect,
what I believe is incorrect marketing of keto
as it relates to the cosmetic effects
and some of the challenges with sleep that some people have.
But some people love keto and it works great for them.
But the ketogenic diet is interesting
because when one shifts to the ketogenic diet,
there is a shift in the gut microbiome
and some people end up feeling better.
Some people end up feeling worse.
Likewise, some people go from ingesting animal products,
including meat or they’re vegetarian and they go to vegan,
and they experience positive shifts in mood and affect.
And we know that the transition to a more plant-based diet
and especially the enrichment of fiber
that’s present in those diets
also creates dramatic shifts in the gut microbiome.
Some people feel better doing that.
Some people feel worse.
And of course, it’s going to depend on whether or not
you’re ingesting a lot of processed foods or not.
There was a paper published in Cell,
a Cell Press Journal, obviously, excellent journal,
showing that ingestion of processed foods,
regardless of whether or not they come from animal sources
or non-animal sources,
the processed foods themselves tend to create activity
within the body.
And this surely has roots in the nervous system
that lead to overconsumption of calories and weight gain,
even some weight gain that couldn’t be explained
by increased calories.
In other words, processed foods are bad
regardless of whether or not you’re talking
about animal products or non-animal products.
Probably not surprising now,
given what you know about these sugar-sensing
and other amino acid-sensing cells in the gut
that we talked about earlier.
So the point of all this is that when I say
you have to find what’s right for you,
that’s not a throwaway statement.
Some people’s microbiome and the lining of their mucosa,
excuse me, their mucosal lining of their throat,
of their gut, of their nose,
everything is improved by diets that are heavily meat-based
and don’t have many plants.
Other people do much better on a plant-based diet
without many meat products or animal products.
It’s highly individual.
And this probably has roots in genetic makeup.
This probably has roots in what people were raised on.
Because remember, the nervous system, of course,
is set up by your genes, your genetic program,
but your nervous system, it adapts early in life
to your conditions.
That’s what it’s for.
The reason you have a nervous system
is to move your body appropriately
towards things that are good for you
and away from things that are not.
But also, it was designed to adapt.
The early life period has this incredible thing
about plasticity that we spent a whole month on
so that it can change so that, yes, indeed,
some people may like certain foods
and react to certain foods better than others
because of the way that their nervous system was wired,
this enteric, as it’s called, nervous system
that lines the gut and that communicates with the brain.
So most of what I’ve talked about today
is black and white.
These are things that are present in all of us,
the sugar-sensing neurons of the gut,
the way the vagus is wired,
the fact that omega-3, omega-6 tend to improve,
the ratios tend to impact mood
with high omega-3, omega-6 ratios improving mood.
We talked about all sorts of things
in the gut-brain and body-brain axis.
But when it comes to the microbiome,
the key thing is that we all have a microbiome.
You want a microbiome,
but you want to promote the microbiome
that is right for you.
And that can be shifted and steered
by ingesting certain categories of foods and not others.
And one thing that really frustrates me
is when the people show up with an agenda
like all-meat agenda or a vegan agenda or a keto agenda,
and they talk about these positive effects
on the gut microbiome, and it’s all true, frankly.
And so it’s highly individual.
Now, this doesn’t get to any of the ethical issues
around animals or the planet
and you hear rabid debates about that on both sides.
And I am not qualified or equipped to talk about
whether or not regenerative agriculture
or animal products or farming or any of these things,
how those actually impact the environment.
That is not my expertise.
But when it comes to your health and your microbiome,
you want to support the microbiome.
It’s very clear that these fermented foods
support the microbiome,
that we should be ingesting at least two servings per day,
which is quite a lot.
That supplementation at low levels can be good.
Supplementation at high levels can create this brain fog,
even though some people say that result is controversial.
I’ve experienced this myself
and the data look to me pretty darn solid.
So that’s one thing to think about as well.
And the other thing about the gut microbiome
is that it’s highly contextual
based on other things that you’re doing.
So even things like exercise and social wellbeing
those things are also impacting the gut microbiome.
So find the diet that’s right for you
and that works for you in the context of the other ethical
and lifestyle choices that are important to you.
That’s my advice.
A note about fasting.
I have a colleague at Yale
who’s an expert in the gut microbiome
and he told me something really interesting,
which is when we fast,
we actually digest certain components
within our dietary tract.
It actually depletes a good amount of the gut microbiome.
And this is interesting.
I’ve had good results from,
I guess you would call it intermittent
or kind of circadian type fasting
where I’ve never done long fast,
but where I push out my first meal by a few hours.
My first meal is generally around lunchtime or so.
But the longer periods of fasting
that go for a day or two or three days
are known to deplete the gut microbiome in major ways.
But that’s not always necessarily a bad thing
because when it’s replenished,
it often is replenished at levels
that exceeded its previous level.
But I think that some of the GI tract
and even some of the mental effects
of returning to eating after feeding,
sometimes people don’t feel so good when they start eating,
they really want food, but then they start eating again,
they don’t feel as good as they did on the fast.
Some of that may be related to the depletion
of the microbiome that occurs during long fast.
So again, this is something to think about
and talk about with your doctor.
But the idea that fasting across the board is good,
there may be some merits to that,
and certainly in some cases,
but it does deplete the microbiome.
And that depletion of the microbiome is significant
because it means when you return to eating,
you’re actually not in the same position
to digest and assimilate those foods.
And those foods are not in the same position
to impact your brain and body
the same way they were prior to the fast.
And this is, I think, why people suggest
a kind of gradual transition back
to consuming nutrients after a fast.
So as we round up, I want to share some results with you
that without question will impact the way
that you respond to food mentally and even physically.
And I know that because that’s the central theme
of the studies I’m about to tell you about.
I have a colleague at Stanford, Aaliyah Crum,
who’s done some remarkable experiments on mindset.
And some people could think about these
as placebo effects or belief effects,
but they actually go way beyond those terms.
And there are a number of different examples of this
that Aaliyah’s lab and her coworkers have demonstrated,
but two that are particularly interesting to me,
I want to share with you now,
because they really emphasize how our beliefs
can really impact the way
that our brain and body work together.
I think the most famous of these is an experiment they did
where they had two groups of individuals,
they were each given a milkshake,
and they had some factors measured from their blood
by an IV while they ingested the milkshake
and then afterwards as well.
And one of the factors that they were looking at
was something called ghrelin, G-H-R-E-L-I-N.
Ghrelin is a peptide that increases with hunger.
So the longer you haven’t eaten, the ghrelin goes up.
And I know some of you say, well, I fast, I fast, I fast,
and I eventually lose my appetite.
Well, ghrelin still goes up and then it drops.
So if you were one of these people
that eats every three hours regularly,
ghrelin kind of gets a little pulse
as you get to that two hour and 50 minute mark.
So it’s a little bit of a timer as well.
It’s a really interesting peptide.
In any event, what they did is they gave people milkshakes,
two groups, one group got a shake
that they were told was a low calorie, healthy shake.
The other group got a milkshake
that they were told was the very decadent high calorie shake
I think it was something like two
or maybe even two and a half times
as many calories as the other, perhaps even more.
I don’t recall the details,
but you had a high calorie and a low calorie condition.
And then they drank the shake
and then they measured ghrelin in these subjects’ blood.
And what they found was that the high calorie shake
had a much more robust effect on blunting ghrelin
and reducing ghrelin.
But the interesting thing you probably guessed already
is that it was the exact same shake given to both groups.
So people’s belief about the content of something
impacted their physiology.
And this speaks to these so-called top-down mechanisms
or modulation of our physiology.
The previous episode about pain,
we talked about the effects of obsessive,
believe it or not, it was kind of obsessive infatuation
and love on pain responses and pain thresholds.
This is yet another example where beliefs
or subjective feelings can impact physiology
at the level of the periphery
because ghrelin is released in the periphery in the body.
Now, these belief effects extend beyond examples like this.
Another good example that I’d like to share
is Allie, Dr. Crumb, and her colleagues did an experiment
where they took housekeepers, hotel,
they were essentially hotel workers,
divide them into two groups.
They had them watch a short film.
In one case, the film was about how their work was important,
it helped people feel comfortable in the hotel,
et cetera, et cetera.
The other group heard that the activity
that they were doing, cleaning and taking care of the hotel
was good for them, it was good for their health,
et cetera, et cetera.
They controlled very nicely in the study
for health parameters, for individual differences,
and for the behaviors of these people
in the period that followed this short tutorial.
What they found was eight weeks later,
the group that had been told
that the activity was good for them
showed lower blood pressure,
they had lost a significant amount of body fat,
and they reported enjoying their work
far more than the other group.
The same work, simply biased mentally
by the information that they were given,
but their physiology followed that information.
And so this is not just the placebo effect,
this is an incredible set of findings
that illustrate the extent to which
whether or not we believe a food
is going to be good for us or not good for us,
well, we can’t escape the reality.
You can’t tell yourself that a poison
is going to be good for you and ingest that poison
and expect it to not kill you,
nor can you tell yourself that eating 12 croissants,
confess I’ve done it,
it was after a very long run, a long time ago,
but you can’t tell yourself
that that’s necessarily going to be good for you
or that it’s going to make you lose weight.
These belief effects are not about lying to yourself.
In these cases, in these experiments,
as you’ll notice,
the subjects didn’t have prior knowledge about ghrelin
or about the effects of their daily routine
on weight loss and blood pressure.
So in order for them to work,
you have to be naive to the information, right?
You can’t simply lie to yourself
and tell yourself what you want to believe.
And that’s important,
but also important is that the mind and the body
are in this fascinating interplay.
And today we’ve talked mainly about
how the body and things that we put inside this tube,
that runs from our mouth to the other end,
to our rectum basically is impacting all these cells,
these neurons, microbiota in there,
mucosal lining, heart, lungs,
and how all that information is feeding up to the brain
to impact how we feel up here.
But also how we feel up here
is impacting how our body reacts
at levels of very core physiology
that you couldn’t just tell yourself
that this was going to work.
But what you believe about certain substances,
certain foods, certain nutrients
does have a profound effect
on the magnitude of their impact.
And sometimes even the quality
and direction of that impact.
Well, first of all,
I want to thank everybody
for their support of this podcast.
The response that we’ve received
since releasing at the beginning of the new year
has been tremendous and we’re so grateful for it.
I know some of you and people you know have said,
well, it’s a lot of information.
It’s like a college lecture.
Indeed, there’s a lot of information,
but I believe very strongly that if you learn mechanism
and maybe even if you hear it several times over,
eventually those mechanisms become embedded
into the way that you view an entire topic.
As well, I always try and put tools as I go along
that you can look to immediately.
Some of them might be right for you.
Others might not.
Try them if you like and don’t if you don’t want to.
And if they don’t work for you, then discard them.
If however, you are finding benefits
from the information and from the tools
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And as mentioned at the beginning of today’s episode,
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If you go to livemomentous.com slash Huberman,
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So today’s episode, we took a full journey
into the brain-body relationship
and discussed a lot of the mechanisms
and the actionable items that you can approach
if you want to explore this aspect of your biology
and psychology further.
Last but certainly not least,
I want to thank everybody for your time and attention today.
And as always, thank you for your interest in science.