Welcome to the huberman Lab podcast, where we discuss science and science based tools for everyday life. I'm Andrew huberman, and I'm a professor of neurobiology and Ophthalmology at Stanford school of medicine.
Today. We are going to discuss salt
also referred to as sodium. Most of us, think of salt as something that we put on and in our food, maybe something to avoid, maybe some of you are actually trying to get more salt. Some of you are trying to get less
salt.
All seem to associate salt with things like blood pressure, Etc. Today. We are going to go down a different set of avenues related to
Salt. We will certainly cover, how salt, regulates blood pressure. We are also going to talk about
how the brain, regulates our appetite for
salt or our aversion for salt. We are also going to talk about how our
sensing of salty tastes actually mediates. How much sugar We crave?
And whether or not, we ingest more or less sugar than we actually need.
So what you're going to learn
Today, is that the, so-called salt system, meaning the
cells and Connections in our brain and body that mediate salt, craving and avoidance are
regulating many,
many aspects of our health and our ability to perform in various context. It was like athletic performance, things like cognitive
performance. We're
also going to talk about aging and dementia and avoiding aging and dementia. And what role salt and salt avoidance might play in that
we're going to touch on some themes that for some of you might seem controversial and indeed, if they are.
Controversial, I'll be sure to highlight them as such. I'm going to cover a lot of new data that point to the possibility.
I want to emphasize the possibility that for
some people.
More salt might help them in terms of health cognitive and bodily
functioning and for other people, less
salt is going to be better. I'm going to talk about what the various parameters are. I'm gonna give you some guidelines that in concert with your physician who you should absolutely talked to before adding or changing anything to your diet or supplementation regime can help you arrive at a salt intake. That's
it's going to optimize your mental physical, health and performance. So we're going to cover neurobiology. We're going to cover
hormone biology wearing, talk about liver function. We're going to talk about kidney function, and of
course, brain function. I'm excited to share this information with you today. I'm certain, you're going to come away with it. A lot of information and actionable items.
I'm pleased to announce that I'm hosting to Live Events. This may the first live event will take place in Seattle Washington on May 17th. The second live event will take place in Portland, Oregon on May 18th.
Sell tickets for these two events are now available at huberman.
Labs.com tour. I should mention that. While I do
hope to visit other cities in the near future to do more Live Events right
now. These are the only two Live Events I've scheduled at least for the next six months. So,
once again, if you go to huberman lab.com tour, you can access the presale tickets. I hope to see
you at these Live Events. And as always, thank you for your interest in
science before we dive into the topic of today's episode. I want to highlight a really exciting new study. This
Is a study from Diego
bojorquez Lab at Duke University. The boar is lab
studies interactions between the gut and the brain and has made some incredible discoveries
of the so called. Neuro pod cells, neuro, pod cells are neurons, nerve cells that reside in our
gut and that detect
things like fatty acids, amino acids, and
some neuro pod cells sense. Sugar previous work from this laboratory. Has
shown that when we ingest sugar
these naropa.
Cells respond to that sugar and send electrical signals up a little wire that we call an axon, through the vagus nerve, for those of you who want to know
and into the brain and through subsequent stations of neural processing evoke. The release
of dopamine, dopamine is a molecule known to promote, craving and motivation and indeed action.
And what these neuro pod cells that send sugar are thought to do is to promote seeking and consumption eating of more sugary.
Foods. Now, the incredible thing is that it's
all subconscious. This is a taste system in the gut that is not
available to your conscious awareness. Now, of course, when you
ingest sweet Foods, you taste them on your mouth too. And so,
part of the reason that you crave sweet Foods, perhaps is because they taste good to you.
And the other reason is that, these neuro pod cells are
driving a chemical craving below your conscious detection. So they're really two
systems. Your gut is sensing at a subconscious level.
In it and sending signals to your brain that work in concert in
parallel with the signals coming from your mouth and your experience of the taste of the food.
Now, that alone is incredible and has been the subject of many
important Landmark papers over the last decade or so, you can imagine how this system would
be very important for things like hidden sugars. When nowadays in a lot of processed foods. They're putting hidden sugars.
They're putting a lot of things that cause your gut to send signals to your brain that make you crave more of those.
Those Foods. So for those of you that really love sugar, just understand.
It's not just about how that Sugar taste.
The new study from the boar has lab deserves attention. I believe
this is a paper published just recently February 25th this year, 2022 in Nature, Neuroscience and excellent journal. And the title of the paper is the preference for sugar over. Sweetener depends on a gut sensor, sell. The borders, lab has now discovered, a neuro pod sell, meaning a category of neurons that can distinguish between
Sweet things in the gut that contain calories,
for, instance, sugar,
and things in the gut that are
sweet, but do not contain calories, artificial sweeteners, like aspartame, sucralose and so forth. There are also, of course, non-artificial non-caloric sweetener, like Stevia monk fruit Etc.
They did not explore the full gallery of artificial sweeteners, what they did find however ought to pertain to all forms of sweet, Nan Chi,
Lauric substances, what they discovered was that there is a signature pattern of signals sent from the gut to the brain. When we ingest
artificial or non-caloric sweetener.
This is important because what it says is that at a subconscious level, the gut can distinguish between sweet,
things that contain calories and sweet things that do not.
Now what the downstream consequences of this sensing is
or what they are, isn't yet clear? Now, I
believe everyone should be aware of these kinds of studies
for
Of reasons. First of all,
it's important to understand that what you craved, meaning the foods you crave in the drinks, you crave is in part due to your conscious experience of the taste of those things, but also due to biochemical and neural events that start in the body and impinge on your brain and cause you to seek out certain things even though you might not know
why you're seeking out more sugar. You find the you're craving a lot of sugar or you're craving a lot of foods with artificial sweeteners and you don't necessarily know why.
Now artificial sweeteners themselves are somewhat
controversial topic. I want to highlight that
someone's back. I described a study from Yale University about how one can condition the insulin system, insulin
is involved in mobilizing a blood sugar and so forth in the body as many of you know, and I describe some studies
that were done from Yale University School of Medicine. Looking at how artificial sweeteners can actually evoke an insulin response under certain
conditions. Now,
Couple of key things. I got a little bit of
pushback after covering those studies and encourage
push back all the time. It's you know, push back
is one of those things that forces all of us to drill deeper into a topic.
I want to be clear. First of all, I am not one to demonize artificial sweeteners. There is evidence in animal models in animal models that artificial sweeteners can
disrupt the gut microbiome,
but those were fairly high doses of artificial sweeteners and it's unclear if the same thing pertains to humans still
unclear. I should say has not been
Been investigated thoroughly.
Some people don't like the taste of artificial sweeteners. Some people do. Some people find that they really help them. Avoid, excessive, caloric intake. Some people believe and yet I should emphasize there still isn't evidence
that they can adjust the
insulin response in all people. I just want to repeat that three times, so that people are clear on that fact.
What these new data emphasize, however, is that we need to understand how artificial sweeteners are
consumed at the level of the gut, or I should say, registered at the level of the
gut and how that changes brain function. Because one thing that I'm familiar with in that many people report is that when they first taste, artificial sweeteners, they taste sort
of not right to them. They don't like the
taste but over time. They actually start to Crave
that taste I've experienced this. I used to drink a lot of diet sodas when I was in graduate school, so to be
aspartame and I
Found that I would need. I actually need them now. Maybe it was the caffeine. Maybe I just like the sweet
taste or the carbonation. We actually have a drive for carbonation, which is the topic of a future episode. But
when I finally quit them for reasons that were independent of any
fear of artificial
sweeteners, I found that I didn't like the taste nowadays. I only occasionally
drink a diet soda. I usually do that farm when I'm playing and there's nothing else available to
me. So I don't demonize them. I
might drink one every once in a while. No big deal. I also want to be clear. I consume Stevie.
The number of different supplements and foods that I consume Stevia. Of course, is a plant-based non-caloric sweetener. So
I myself consume artificial sweeteners, many people hate them. Many people like them and find them
useful for their nutrition. And in fact to keep their caloric intake in a Range, that's right for them.
And many people like myself are curious about them and somewhat wary of them and yet continue to
consume them in small amounts. I think most people probably fall into that category. I
should also mention that many food
manufacturers.
Put artificial sweeteners, such as sucralose
Etc into foods and it's always been unclear as to why they might want to do that. And yet, we know that the sweet taste consumption, even if it doesn't contain calories can drive more craving of sweet food. So there may be a logic or a strategy to why they do that.
Again, a topic for exploration on today's podcast and in future podcast because where we're headed
today is a discussion about how salt and salt sensing both.
Consciously and unconsciously can adjust our craving
for other things like sugar and water and so on.
So I want to highlight this beautiful work from the Boris lab will put a link to the study. I want to open this as a chapter for further exploration. I like to think that the listeners is of this podcast are looking for answers where we have answers, but are also I would hope excited about some of the new and emerging
themes in what we call Nutritional neurobiology and indeed the bore is lab
really stands as one of the Premier Laboratories out there that's looking
At how Foods as consumed in the gut
are modifying, our nervous system, the foods We crave and how we utilize those Foods. Before we begin. I'd like to emphasize that 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. I'd like to thank the sponsors of today's podcast. Our first sponsor is
athletic greens now called a G1. I've
been taking a G1 since
Well, so I'm delighted that they're sponsoring the podcast. The
reason I started taking a G1 in the reason I still take a G1 once or twice a day is that I find it to be the best way to ensure. I get all of my
vitamins and minerals and the probiotics. I need I try and eat really well, but I'm not perfect about it. And with that let it greens. Ag1. I cover any deficiencies. I might have
the probiotics are particularly
important to me because as we've talked about on
many previous episodes and we'll talk about more on today's episode the gut microbiome.
Is supported by probiotics and the gut microbiome supports many biological functions.
Important for immediate and long-term health
things like immune system function,
things like the gut brain axis and mood and appetite. And so
forth with athletic greens. I make
sure all of those bases are covered because of the probiotics. If you'd
like to try out, let it greens. You can go to athletic greens.com huberman, to claim a
special offer. The give you five free travel packs, which make it really easy to mix up athletic greens while you're on the
road and they'll give you a year supply of vitamin D3 K to vitamin D3 is.
For many aspects
of our immediate and long-term health. And many people simply are not getting enough vitamin D3 or the amounts that are getting are not optimal.
K2 is important for cardiovascular health and for calcium regulation. So again, if you go to athletic greens.com huberman, you can claim the special offer, the five free travel
packs and a year supply of vitamin D3 K to
today's episode is also brought To Us by element. Element is an electrolyte drink, that has everything you need and none of the things you don't. That means it has
Salt magnesium and
potassium, so called electrolytes, which are critical for
neuronal function and a
lot of other biological
functions. As I mentioned on the podcast before, I'm a fan of salt. I believe in ingesting appropriate, amounts of salt. And by appropriate, I mean, depending on
what your background blood pressure happens to be what your activity levels, are how much you sweat, what your cognitive and physical demands are today. We're going to talk about how to determine what those needs are.
I'm always trying to stay on
top of my hydration and as you'll also learn about today,
Salt and water intake, and hydration are intimately related with element. I'm sure to get the
potassium, the sodium and the Magnesium that I need. And I do that in a great tasting drink. And as I mentioned before, it has no
sugar. If you'd like to try element, you can go to drink element.com. That's drink LMN t.com huberman to claim a free element sample pack, you only cover the cost of shipping. Otherwise, it's completely free again. That's drink element. LMN t.com
huberman to claim a free.
Sample pack of element.
Today's episode is also brought To Us by inside tracker. Inside tracker is a personalized nutrition platform that analyzes data from your blood and DNA to help. You better understand your body and help you reach your health goals. I am a big fan of
getting regular blood work done and I've been trying to do it as much as I can afford for years. The reason is that many of the factors that impact our immediate and long-term Health
can only be discovered
from a quality blood tests with most
blood tests and DNA tests. However,
you get information back, but not a lot of information about what to do with those numbers. So if something's in high or low range, you might get one or two generic recommendations, things that you could easily look up online, but you're not going to get a lot of
specific recommendations
with inside tracker. They give you a lot of specific recommendations as to Lifestyle factors and nutrition factors, supplementation factors things. You may want to add to your life or things. You may want to delete from your life in order to bring the
numbers into the ranges that are best for your immediate and long-term Health. There's simply no replacement for these kinds of
Data, and your data are the most important data to you and quality blood tests and DNA tests are the way to access them.
If you'd like to try inside tracker, go to inside tracker.com huberman to get 20% off any of
inside trackers plans. That's inside
tracker.com
huberman to get 20% off. Okay, let's talk
about salt, salt has many, many important
functions in the brain and body. For instance. It regulates fluid balance. How much fluid you desire? And how much fluid, you excrete. It also?
Regulates your desire for salt itself. Meaning your salt appetite. You have
a homeostatic, Lee driven salt
appetite. I'll talk about the mechanisms today, make them all very clear.
What that means is that you crave, salty, things Beverages and Foods
when your salt stores are low
and you tend to avoid
salty Beverages and Foods when your salt stores are high, although, that's not always the case. There are circumstances where you will continue to crave salt, even though you don't need salt or
Indeed, even if you need to eliminate salt from your system,
salt also regulates your appetite for other
nutrients, things like sugar, things like carbohydrates. And today, we'll explore all of
that. Technically, salt is a mineral and I should mention that. When I say salt, I am indeed referring to sodium in most cases. Although, I will be clear to distinguish salt from
sodium. Meaning for table salt from sodium. Most people
don't realize this, but one gram of table salt contains.
About three
hundred and eighty eight milligrams of sodium. So technically we should be talking about sodium today and that
salt. I will use them interchangeably unless I'm referring to some
specific recommendations or ideas about trying to Define your ideal salt AKA sodium intake. Okay. So this is important. I think right off the bat, a lot of people get themselves into a place of confusion and potentially, even to
a place of trouble by thinking that table salt in grams.
Always equates to sodium in grams and that's simply not the case.
Today. We're going to explore the neural mechanisms
by which we regulate our salt appetite and the way that the brain and body interact in the context of salt, seeking salt avoidance, how to determine when we need more salt, when we need less salt will talk about kidney function will get into all of it. And we're going to do it very systematically.
So let's start in the brain. We all Harbor small
sets of
of neurons, we call these sets of neurons nuclei meaning little clusters of neurons,
that sense the levels of
salt in our brain and body. There are a couple brain regions that do this and these
brain regions are very, very special special because they
lack biological fences around them that other brain areas have and that those fences, or I should say that fence goes by a particular name and that name is the blood-brain barrier or BBB
most substances
that are sir.
Collating around in your body,
do not have access
to the brain, in particular, large molecules. Can't just pass into the brain.
The brain is a privileged organ. In this sense, there a couple other organs that are privileged
and that have very strict barriers, very
particular fences. If you will those other organs include things like the ovaries
and testes and that makes sense. For the following reason. First of
all, the brain at least
most of the brain cannot regenerate after injury. You just simply can't.
A place brain cells after injury. I know people get really excited about neurogenesis the birth of new neurons
and indeed neurogenesis has been demonstrated in
animal models and to some extent, it exists in humans in a few places. For instance, the olfactory bulb where neurons are responsible for detecting odor, into the environment for smell that is and in a
little sub region of the hippocampus a memory area.
There's probably some neurogenesis, but the bulk of really good data out there point to the fact that in humans, there's not much turnover of
neurons. What that?
Is that the neurons you're born
with are the ones that you're going to be using? Most, if not all of your life. In
fact, you're born with many more neurons than you'll have later. And there's a
process of naturally occurring, cell death, called apoptosis that occurs during development. So, you actually are born with many more neurons than you have later in life. And that's the reflection of a normal healthy process of nerve cell, elimination estimates vary, but anywhere from, you know, a third to maybe even half or even two-thirds of
Neurons depending on the brain area just going to die across development. That might sound terrible. But that's actually one of the ways in which you go from being kind of like a little potato bug, flopping around helplessly in your crib to being an organism that can walk and talk and articulate and calculate math or do whatever it is that you do for a living. So the brain has a set of elements, these nerve cells and other cells and it needs to use those for the entire lifespan.
So having a BBB, a blood-brain barrier
around the brain is absolutely critical.
The ovaries and testes, have a barrier for, we assume the reason that they contain the genetic material
by which we can pass on our genes to our Offspring. Progenies meaning, make children and those children will have our genes or at least half of them the other half from the partner, of
course.
If the cells within the ovaries and testes are mutated. Well, then you can get
mutations and Offspring. So that's very costly in The evolutionary sense. So it makes sense that you would have a barrier from the blood. So if you ingest what's called a mutagen, if you ingest something that can mutate, the genes of cells, you can imagine why there would be a
premium on not allowing
those mutagens to get into the brain, the ovaries of the
testes. Okay. So the brain has this BB this blood-brain barrier around it, which makes it very, very hard for some
This is to pass into the brain. Unless those substances are very
small or those substances and molecules
are critically required for brain
function. However, there are a
couple of regions in the brain
that have a fence around them. But that fence is
weaker. Okay, it's sort of like going from a really big wall, thick. Electronic 24-hour, surveillance fence where nothing can pass through. Accept, only the exclusive cargo that's allowed to go
through, to having a little
Clone fence with a
couple holes in it or it's a kind of a picket fence that's falling over
and substances can move freely in from the blood
circulating in the body into the brain. And it
turns out that the areas of the brain that monitor
salt balance,
and other
features of what's happening in the body. At the level of what, we call osmolarity at
the concentration of salt reside in these little sets of neurons that sit, just on the other side of these weak fences
and the
Most important and famous of these for its sake. Of today's
conversation is one called 0, VL,
t 0, V, LT stands for the organum. Vascular system of the lateral. Terminalis hit is what's called a circumvent, tricular, organ-y circumvent regular. Well, not to bog you down with their Anatomy, but your brain is a big squishy mass of neurons and other cell types, but it has to be nourished and through the middle of that
brain. There is a tube. There's a hollow that creates spaces and those spaces are called.
Ventricles, the ventricles are spaces in which
cerebral spinal fluid
circulates and it nourishes the brain. It doesn't number of other things as well.
The circumvent regular organs are areas of the brain that are near that
circulating fluid and that circulating fluid
has access to the bloodstream in the bloodstream has access to it and this structure that I'm referring to oh VLT, organum bass, callosum of the lateral terminalis has neurons. That can sense. The con, the contents of the
Blood. And to some extent, the cerebral spinal fluid. There are a couple other brain areas that can do this as well.
They go also, by the name of circumvent tricular
organs and I'll talk about the
names of some of those other areas. But
for today, and I think for sake of most of the discussion, understand that the 0 V LT is special. Why? Because it doesn't have this thick
barrier fence which sounds like a bad
thing and yet it's a terrific border detector the neurons in that region are able to
Pay attention to what's passing through in the bloodstream and can detect for instance. If the levels of sodium in the blood stream or too low, if the level of blood pressure in the body is too low or too high and then the oh VLT can send signals to other brain areas. And then those other brain areas can do things like release hormones. That can go and act on tissues in what we call the periphery in the body.
And for
instance, have the kidneys secrete more urine to get rid of
salt. That's it.
Excessive salt in the
body or have the kidneys. Hold on to your end to hold on to whatever water or
fluid that one might
need. So before I go any deeper into this pathway just understand that the 0 V LT has a very limited barrier.
It can detect things in the bloodstream and this
incredible area of the brain almost single-handedly sets off the Cascades of things that allow you to regulate your
salt balance, which turns out to be absolutely. Critical,
not just for your ability to think and for your neurons to work, but indeed for all
Love life. If the 0 V LT doesn't function
correctly or effectively dead or dead soon. So this is a very important brain region.
So let's talk about the function of the oh, VLT and flesh out some of the other aspects of its circuitry of its communication with
other brain areas. And with the body, in the context of something that we are all familiar with which is thirst.
Have you ever wondered just why you get thirsty? Well, it's because neurons in
Euro VLT are
detecting changes in your bloodstream, which detect Global changes within your
Body, and in response to that Euro V LT sets off certain events within your brain and body that make
you either want to drink more fluid or to stop drinking fluid.
There are two main kinds of thirst. The first one
is called osmotic thirst and the
second is called hypovolemic thirst.
Osmotic thirst has to do with the concentration of
salt in your bloodstream.
So let's say you ingest something very, very salty. Let's say you ingest, you know, a big bag of.
I'd confess. I don't eat these very often but I really like those kettle. Potato chips. And they're pretty salty. I've never actually measured how much sodium is in them. Sure. The information. Is there every once in a
while. I'm particularly interested in doing. So, I'll
just down a bag of those things and I really like them and they're very salty,
but they almost always make me feel thirsty. And the reason is that by eating
Those, I've been just a lot of sodium,
again, not a frequent occurrence for me,
but happens, every now, and again, and I don't have too much Shame about that because I think I have a pretty healthy
relationship to food and I enjoy them. And I understand that it will drive salt levels up in my bloodstream and
that will cause me to be thirsty. But why
why? Because neurons in the 0 VL
T. Come in two main varieties, one variety senses, the osmolarity of the blood. That getting a
Across that weak little fence that we talked about before. And when the osmolarity, meaning the salt concentration in the blood is
high it activates these specific neurons in the O
VLT. And by activates, I mean, it causes them to send electrical potentials
literally send electrical signals to other brain areas and those other brain
areas inspire a number of different Downstream events. So what are those other brain areas? Well, the oh
VLT.
Signals to an area,
called the supraoptic, nucleus the name, and why it's called the super optic. Nucleus is not necessarily
important. It also signals to the so-called paraventricular nucleus, another nucleus that sits near the ventricles and can monitor the qualities that chemical qualities of the cerebrospinal fluid, as well as probably the bloodstream as well. And the consequence of though, that communication, is that a particular hormone is eventually
Released from the posterior pituitary. Now the
pituitary is a gland that sits near the roof of your mouth. It releases all sorts of things like growth hormone and luteinizing hormone luteinizing, hormone will stimulate things like estrogen and testosterone production and release from the ovaries and
testes. And so on the pituitary has a bunch of different compartments and functions, but what's really cool about the
pituitary is that
certain regions of the pituitary actually contained the axons. The
Dwyer's of neurons and the neurons reside in the brain. And so the supraoptic nucleus gets a signal from the O VLT. The signal is purely in the form of electrical activity. Remember neurons aren't talking in one. Another about
what's happening out there. They're not saying hey,
there's you know too much salt in the bloodstream. Let's do something about it. All they receive are our
so-called action potential waves of electricity.
The neurons in the supraoptic, nucleus, then release their own electrical signals.
Then the pituitary and some of those neurons and nearby neurons are capable of releasing
hormones as well as electrical signals.
So from the pituitary, there's a hormonal
signal. That's released called vasopressin
vasopressin also goes by the name, antidiuretic hormone and antidiuretic hormone
has the capacity to
either restrict the amount of urine that we secrete or when that system is turned off.
To
increase the amount of urine that we secrete.
So there's a complicated set of Cascades that's evoked
by having high salt concentration in the blood. There's also a complicated set of Cascades that are evoked by
having low
concentrations of sodium in the blood,
but the pathway is nonetheless, the same it. So VLT is detecting,
those osmolarity changes communicating to the
supraoptic nucleus. Supraoptic nucleus is
either causing the release of or is releasing vasopressin.
An antidiuretic hormone or that system is
shut off. So that the antidiuretic hormone is not secreted
which would allow urine to flow more freely. Right? Antidiuretic means anti release of urine and
by shutting that
off, you are going to cause the release of urine, your sort of allowing a system to flow. So to
speak. The second category of thirst
is hypovolemic thirst hypovolemic, thirst occurs, when there is a drop in
in blood pressure.
Okay. So the 0 V LT, as I mentioned before can sense
osmolarity.
Based on the fact that it has these neurons that can detect how much salt is in the blood stream,
but the 0 VL. T.
Also Harbors neurons that are of the
baroreceptor mechanoreceptor category. Now more
on baroreceptors in mechanoreceptors later,
but baroreceptors are essentially a
receptor, a meaning, a protein that's in a cell that
responds to changes in blood pressure. So
There a number of things that can cause decreases in blood pressure.
Some of those include, for instance, if you lose a lot of blood,
right? If you're bleeding, quite a lot, or
in some cases, if you vomit
quite a lot, or if you have extensive diarrhea or any combination
of those and there are other things that can
reduce blood volume and we will talk about some of those
later. But in the classic case of hypovolemic, thirst one is simply
losing blood and therefore blood pressure goes down. So, very simple to imagine your mind. You have these pipes, which are the arteries veins and capillaries. And when
You lose some blood volume, the pressure in those arteries veins and capillaries goes down. Oh VLT has neurons. I can sense that reduction in blood pressure because of the reduction because of the presence of baroreceptors in, oh VLT.
There are other elements that also play into the response to
what we call hypovolemic thirst.
For instance.
The kidney will secrete something called, renin renan will activate something called Angiotensin 2.
To from the lungs of all things. Amazing and Angiotensin 2 itself can act on
oh, VLT organum bass, callosum of the lateral
terminalis, which in turn will create thirst. Okay, so in both cases, right the osmolarity sensing system
meaning osmotic thirst and in hypovolemic thirst where blood pressure has dropped.
The end result is a
desire to drink more
and that desire to drink more comes through a
variety of Pathways that are both.
Actin indirect include vasopressin, and don't include vasopressin.
But I think for just sake of General example,
and even for those of you that don't have any biology background or physiology background,
just understand that there are two main types of thirst. Both types of thirst. Oz. Osmotic thirst, in hypovolemic. Thirst are not just about seeking water, but they also are about seeking salt.
In very general terms salt, a case sodium can help retain water. Now, that doesn't mean that salt always retains water. If you have excessive amounts of
salt, will you retain excessive amounts of
water? Well, sort of as it will soon. Learn. It's all contextual. But for most cases, we can say that by having salt in our system
our brain and our body can function normally provided the levels of salt are adequate and not too high or too.
Too
low and thirst. While we often think of it as just a way to bring fluid into our body is designed as a kind of a interoceptive perception, what I mean by that interception as many of you know, now
from listening this podcast is a
paying of attention or a recognition, rather, a conscious
recognition of the events going on within
our body. So when we are thirsty, it's a certain form of interception. We go. Oh,
I need something or I crave. Something. You may not know exactly.
Lee what you
need, but when you are thirsty, you're not just seeking
water. You're also seeking to balance your osmolarity, which means you may be seeking salty
fluids or
Foods. In some cases, you'll try and accomplish this by
eating, or it may be that you're trying to avoid, or you will be inspired to
avoid salty fluids and foods,
but if you want to understand
sodium and it's roles in the body, you have to understand thirst. And if you want to understand thirst, you have to understand.
How fluid balance is regulating the body, that's not surprising at all,
but sodium and water work together. In order to generate what we call thirst sodium, water work together. In
order to either retain water or Inspire us to let go of water to urine it. So before we can dive into the specifics around Salt and how to use salt for performance and various recommendations and things to avoid. We need to drill a little bit deeper into this fluid balance mechanism.
In the body. And for
that reason, we have to pay at least a little bit
of attention to the kidney. The
kidney is an incredible organ. And one of the reasons, the kidney is so amazing is that it's responsible for both retaining holding onto or allowing the release of various
substances from the body substances, like glucose or amino acids
urea uric acid.
Salt, potassium, magnesium. It's basically a filter, but it's a very, very
intelligent filter intelligent. Meaning. It doesn't have its own mind. But the way it works is is really
beautiful, basically, blood enters the kidney and it goes through a series of tubes, which are arranged in two Loops. If you want to look more into this, there's the
beautiful Loop of
henle and other aspects of the kidney design that allow certain
Substances to be retained and other substances to be released depending on how concentrated those
substances are in the blood.
The kidney responds to a number of hormonal signals, including vasopressin in order to, for
instance, antidiuretic hormone in order to hold on to more fluid. If that's what your brain and body
need, and it responds to other
hormonal signals as well. So it's a
pretty complex organ. Nonetheless. There's a key point, which I already mentioned.
I think most people don't realize that there's actually something that I like to tell kids. When I meet them
provided that their appropriate age. I'll say
oftentimes with kids, learn all my
scientists. They'll they'll ask a question about something related to science and hopefully for my sake it's something about Neuroscience
but one thing that I'll tell kids I'll
say, you know, do you know that your urine your pee is actually filtered blood and
occasionally that will really terrifying a kid, but that also occasionally really terrifies an adult but indeed.
Need your urine is
filtered blood. Basically blood gets into the kidney. The kidney
is going to filter out. Certain things, certain things are going to be allowed to
pass through and others are not.
Okay. So the way the kidney is designed is that about
90% of the stuff that's absorbed from the blood is going to be absorbed early in this series of tubes
and only a small percentage is going to be regulated or worked out as you get
into What's called the distal kidney. We distal just means the further the furthest part away. Okay, the
Proximal is up close. So like your shoulder is proximal to your
midline of your body. And your hand is distal. So, in biological terms, you hear about proximal distal, which was just means near or far
from. So, just to give a really simple example. Let's say that you are very low on fluid.
You haven't had much to drink in a while. Maybe you're walking around on a hot day.
Chances are that the neurons in Euro V, LT will sense. The increase
in osmolarity. Write the concentration of salt is
Going to be increased relative to the
fluid volume that's
circulating this of course assumes that you haven't excreted a lot of sodium for one reason or another.
But that increase in osmolarity is
detected by the oh VLT, the 0 V LT is going to Signal a bunch of different Cascades through the supraoptic
nucleus etcetera. And then vasopressin is going to be released into the bloodstream and vasopressin again, also called antidiuretic hormone is going to act on the kidney and change the kidneys function.
In a couple of different ways. Some mechanical some chemical. Okay, in order to make sure that your kidney does
not release much water, doesn't make, you want to urinate. And in fact, even if you would try to urinate your body's going to tend to hold on to its fluid stores.
Okay, so very simple, straightforward example, we can also give the other example, whereby, if you are ingesting
a lot, a lot, a lot of water. And it's not a particularly hot day, and you're not sweating very much. Let's assume your salt intake is constant.
Or or is low for
whatever reason. Well
then the osmolarity, the salt concentration in your blood is going to be lower Euro, V, LT will detect that because of these Osmos and seeing neurons in Euro VLT.
Your OB LT will fail to
signal to the supraoptic nucleus. And there will not be the release of a suppressant antidiuretic hormone and you can excrete all the water that your body wants to excrete. Meaning, you'll be able to urinate.
Holding onto water at the level of the kidney.
Okay, very simple examples, but hopefully it illustrates how events within
the blood, meaning the concentration of salt relative to the amount of fluid, right? That's what I was molarity
is is detected by the 0 VL, T. The brain then communicates to the pituitary.
The pituitary sends a hormone out into the blood and the
hormone acts on the kidney
to either hold onto or let go of fluid, meaning to prevent you from wanting to urinate or from stimulating. You to want to urinate.
Nate
very very simple
kind of yes, no type situation here. There's a lot of nuance to this in reality. There are a lot of other hormones in this pathway, but I think for least the stage of the discussion that should be sufficient.
Some of you may have
noticed that a molecule. We've been talking a lot about today,
vasopressin was also mentioned on a previous episode of The
huberman Lab podcast, but in a very different context molecule, I'm referring to is vasopressin and mentioned. It's a hormone involved in anti diuresis.
Meaning preventing urination. It's an antidiuretic.
But we also talked about vasopressin in the
context of Desire. Love and attachment. We talked about in the context of monogamy and non-monogamy. In a species of animal called the Prairie vole. You can check out that episode. I believe vasopressin and the non-monogamous Prairie voles are mentioned in the timestamp. So should be easy to
find vasopressin is
made at multiple locations.
Ins in the nervous system, mainly the supraoptic, nucleus and indeed.
It's also involved
in aspects of sexual behavior and mating. Now, it does that through mechanisms that are distinct from its antidiuretic
effects. In fact, there are people and who take vasopressin as an
aphrodisiac. Now, I'm certainly not suggesting people do that. But I have all the confidence in the world. That the moment I talked about Visa.
Listen, someone in the comments is going to say, what do you think about vasopressin nasal sprays in this kind of thing
vasopressin and indeed, oxytocin, another hormone that's
involved in pair bonding and various aspects of brain and body function
are available as
nasal sprays, that can get up into the deep recesses of the brain and you can impact some of these core. What we call hypothalamic functions, these primitive drives and hypothalamic functions.
I would encourage a lot of caution.
Maybe even Extreme Caution in regard.
Recreational use of things like vasopressin and oxytocin less, you are working with MD and MD, scuse me, and they prescribe it, or they really know what they're
doing. These are powerful hormones
that have a lot of different effects on the brain and body. The way that vasopressin, meaning antidiuretic hormone
prevents the release of
fluid as urine from the body is pretty interesting, it acts directly on the kidney. So as I mentioned before, blood flows into the kidney, a number of things are retained in the early part
of the kidney vasopressin,
Acts at a fairly distal meaning kind of end, endgame part of the of the loops of tubes through the kidney and it increases the permeability of those tubes. In other words. It makes sure that the fluid that would otherwise pass into a collecting duct and then go out to the bladder, never
actually makes it to the bladder.
I point this out because what antidiuretic hormone does is it
prevents the bladder from filling it all. It's not as if it locks fluid in the bladder and prevents you from urinating. I think the way I've been
In describing things up until now. And the way you'll hear about antidiuretic hormone. It might sound like it and a locks up the bladder prevents you from being able to urinate. But you have a full bladder. That would be very uncomfortable. That's not the way it works. It actually causes the
tubes headed towards the bladder, from the kidney to become permeable. Meaning to allow fluid to go back
into the bloodstream, into the rest of the body. So that fluid never actually fills the bladder and so you never feel the urge to
urinate. Now. This is an episode about salt, a key thing to understand about the
Sydney. Is that the kidney uses sodium in order to
conserve water which has everything
to do with the fact that sodium can actually hold water put differently water tends to follow sodium. So where we have sodium, we tend to have water and sodium. When it's concentrated, can hold onto water and that's one of the main ways that the kidney holds onto water
in the body and as will soon, learn it is, there is no
simple and direct formula.
Le to say for instance, okay, if salt levels are high, a lot of water is
retained. And if salt levels are
low, a lot of water is released on the one hand that can be true, but it's also the case because these systems are homeostatic, meaning they're always seeking balance both within system, within the
salt system and between systems, the salt and water system. It's also the case often
that if we have enough sodium, well, then we can see.
Eat sodium and some
water will follow or if we don't have enough sodium,
then yes, indeed because we're not holding onto water. More fluid can be excreted. But if that condition of low sodium, last long enough, then we start to retain
water because the body recognizes, ah,
salt is low and water is being excreted and eventually a system will kick in to retain water. So I'd love to give you a simple black and white
yes or no answer for
Low, sodium, high, sodium, moderate sodium, and water balance, but it's all
contextual. And when I say contextual, I mean it will depend
on blood pressure, hypertension prehypertension. If that's their maybe
normal tension, hormone levels, exercise, etc. Etc. A pretty good example of how complicated this can all be is one that some of you may be familiar with it's pretty well known that during certain phases of the menstrual cycle. When estrogen and progesterone and other hormones are fluctuating that.
Water can be retained in the body. There's it's what's called edema or swelling some time. So the common assumption and indeed, it can be true that when estrogen levels are high. There's water retention in the body. Also, in males of estrogen levels are high, there can be water retention in the body. This is one of the reasons why athletes and in particular bodybuilders who take anabolic steroids, like testosterone which can be converted into estrogens. Sometimes they'll look the walk around. They look like they were partially inflated. They look like they're going to pop.
It's in. Its, it looks like a swelling of the skin, not just because they have large muscles and that's not always, but often water retention due to testosterone conversion into estrogen.
Now that all sounds
consistent right? Estrogen levels fluctuate in the menstrual cycle in males, where there's an increase in estrogen. There's retention of water, but actually estrogen acts as a diuretic.
So one would think
okay, when estrogen levels go up, there should be a lot of fluid
excreted but I bring up this example to point out that it's a very complicated and
dynamic balance.
Between hormones and salt and fluid. You
can't draw a one-to-one
relationship there,
and that turns out to be a very important point. And we can use that not as a way to further complicate things. But as a way to understand under which context
less sodium intake or more sodium and take can be beneficial. So that's why I'd like to turn our attention now. So how much salt do we need? And what can we trust in terms of trying to guide our ingestion of salt?
First of all,
I want to be very, very clear that there are a number of people out
there that have pre hypertension or
hypertension. You need to know. If you have pre hypertension or
hypertension. You need to know. If you have normal tension, meaning, normal blood pressure.
Everyone should know, their blood pressure
is absolutely crucial measurement, that has a lot of impact on your immediate and long-term Health outcomes. It informs a lot about what you should do. Should you be doing more cardiovascular exercise? Should you be ingesting more or less?
Alt, should you be adjusting any number of different lifestyle factors? So you need to know that and without knowing what your blood pressure is? I can't give a one-size-fits-all recommendation and indeed. I'm not going to give medical recommendations. I'm simply going to spell out what I know about the research, which hopefully will point you in the direction of figuring out, what's right for you in terms of salt and indeed fluid intake.
There is a school of thought that everybody is consuming too much
salt. And I do want to
highlight the fact that there are
Dozens, if not hundreds of quality papers that point to the fact
that a quote-unquote high-salt diet can be bad for various organs and tissues
in the body including the
brain. It just so happens that because
fluid balance, both inside and outside of cells is crucial. Not just for your heart and for your lungs and for your liver and for all the organs of your
body, but also for your brain that if the salt concentration
I'd of cells in your brain becomes too high
neurons suffer, right? They will draw fluid
into those cells because water tends to follow salt.
As I mentioned before, and those cells can swell.
You can literally get swelling
of brain tissue. Conversely if salt levels are
too low inside of cells, in any tissue of the body, but
in the brain included, then the cells of the body and brain can
Shrink because water is pulled into the extracellular, space
away from cells. And indeed, under those conditions,
brain function can
suffer, and indeed the overall health of the brain can suffer. So
there are many reports out there, indicating both an experimental models, and to some extent in humans that overconsumption of salt is bad for brain function and Longevity. And yet, there is also
decent evidence in both.
Models. And humans that if salt consumption is too
low, then brain Health
and Longevity will suffer as will other organs and tissues of the body.
So, like most things in biology, you don't want things too high or too low. Now, I would say that the vast majority of studies out there point to the fact that
a high-salt diet is detrimental to brain health and function.
Most of the studies have focused
on that aspect of salt balance and
its consequences on brain
function.
One
critical issue with many of those studies.
However, is that the high-salt diet is often coupled to other elements
of diet that are also unhealthy. Things like excessively high levels of carbohydrates or fats or combinations of carbohydrates and fats.
And so while I know there are many burning questions out there about how much
salt one needs if they are on a low carbohydrate diet or if they are fasting or if they are on a vegan diet, there
have simply not been many studies that
I've explored the low moderate and high salt conditions on a backdrop of very controlled nutrition. And that's probably reflective of a fact
that there are not a lot of very
well-controlled nutrition studies out there. There are some of
course, but it's very hard to get people to adhere to nutritional plans in a very strict way and to do
that for sufficient periods of time that would allow that the various Health outcomes to
occur. Nonetheless. There's some interesting reports that indicate that
the amount of salt intake can indeed predict Health outcomes
or what we call hazardous events, things like cardiovascular events and stroke and
so forth. And what's interesting is that indeed a lower. I'm not
saying low, right? Because I don't believe that you want your diet to be truly low in anything except perhaps poison, but
a lower salt diet can reduce
the number of these.
So called hazardous
events, but it's a somewhat of a shallow u-shaped function such that yes indeed. A high
salt intake can be very detrimental for your health. Both in terms of cardiovascular events, stroke and other deleterious health events,
but somewhere in the middle that actually sits quite to the right meaning higher
than what is typically recommended. For salt intake can actually reduce.
The number of these hazardous events at least
some reports point to that. And so I want to
emphasize what one of those particular reports
says and I also want to be sure to counter it from the perspective of the context of that
study was set in. Because again, my goal here is not to give you a strict set of recommendations at all is to point you to the literature try and make that literature as clear as possible and allow you to evaluate for yourself. And I don't just say that to protect us. I say that to
protect you because indeed you are
responsible for
Your health and your health choices,
so the paper that I'm referring to is a very interesting one. We, of course, never want to put too much weight on anyone report. But this is a paper that was published in 2011, in the Journal of the American Medical Association. The title of the paper is urinary, sodium and potassium excretion and a risk of cardiovascular
events. We have not talked much about potassium yet,
but sodium and potassium tend to work in concert in the brain and body in order to regulate various
physiological.
Functions in health and we'll talk more about potassium as time. Goes on
the key plot or set of data in this study. For those of you who want to look it up. We will link to
it. There are a lot of data in here
but is Figure 1 which is basically evaluating the amount of urinary excretion of
sodium. Which is a
somewhat indirect. But nonetheless valuable measure of how much sodium people were ingesting and plotted against that is what they call the highwomen.
Hazard ratio and Hazard ratio points to the composite of cardiovascular, Death Stroke, myocardial infarction and an infarct is an injury and hospitalization for congestive heart failure. And what it points to is the fact that the hazard ratio is low ish at sodium excretion of about 2 grams per day, but then continues to go down until about four point five, two five.
Five grams per day. That remember this is sodium excretion. So it's reflective of how much sodium was in
the body. Which is reflective of how much sodium was ingested.
And then the hazard ratio increases fairly dramatically a very steep slope heading anywhere from seven to eight to ten
and out towards, you know, 12 grams of sodium excretion per day.
So the simplest way to interpret these data are that at fairly low levels of sodium, meaning it
about 2 grams per day.
You run fewer health risks, but the number of risk continues to decline As you
move towards 4 and 5 grams per day.
And then as you increase your salt intake further, then
the risk dramatically increases.
So no study is Holy nor is any figure in any study
or any collection of studies. Holy
rather. We always want to look at what the bulk of data in a particular
field reveal.
Nonetheless. I think that the
plot that we described meaning the graph that we described is
pretty
Staying in light of the 2020 to 2025 dietary recommendations for Americans, which are, which is that people consume no more than two point three grams. Meaning 2,300 milligrams of sodium per day. That's about a half a teaspoon of salt per
day.
Now, most people are probably consuming more than that because of the fact
that they are ingesting processed foods and processed.
Foods tend to have more salt in them than non-processed Foods. Now, of course that's not always the case, right? Sea salt is not a processed food in most cases
and there are a lot of
unprocessed foods that can be high in sodium but processed foods. In particular tend to have a lot of sodium. You can see the simply by looking at the packaging of any number of different foods,
but if we are to take this number 2, .3 G, that's the
recommended cutoff for ingestion of sodium.
It actually falls in a portion of the curve that we were talking about a moment ago. That indeed is associated with low
hazard out, low low, incidence of hazardous outcomes, cardiovascular events, stroke
Etc. But the ingestion, according to that plot, the ingestion of four or five
grams of sodium,
almost double or more sodium
than is currently. Recommended is associated with even lower numbers of
Hazardous events.
So we need to think about this. And we need to explore it in the context of other studies, of course, and we need to evaluate it in terms of this thing that we've been going back to again. And again, which is context right? These recommendations of 2.3 gram per day cutoff is in the context of a landscape where
some people do indeed, have hypertension or prehypertension. The incidence of hypertension is gone up dramatically in the last 100 years.
And seems to continue to go up whether or not, that's because of increased salt intake, or whether or not, it's because of
increase salt intake and other things such as highly processed foods
that isn't clear again, pointing to the The Challenge and doing
these epidemiological studies
and really parsing what
aspects of a change in some health metric is due to, for instance, the ingestion of more sugars versus more salts or simply because of the ingestion of more
salt. It's a complicated.
Almost barbed wire topic by now, but we can start to pull apart that barbed wire tangle and start to evaluate some of the other
people in other conditions that exist out there, maybe for you that
actually warrant more sodium intake and we're more sodium
intake, might actually be
beneficial. So again, I want to be very,
very clear that you need to know your blood pressure. If you have high blood pressure or your pre-hypertensive, you should be especially cautious about doing anything that increases your blood pressure.
And as always, you want to, of course, talk to your doctor about doing anything that could adjust your health in any direction.
But nonetheless, there are some important papers have been published. In recent years. I want to point to one of them in particular. This is a paper that was published in the journal autonomic
Neuroscience basic and clinical
because this paper like several other papers ask the question and indeed they asked the question in the title. It's a review dietary sodium and health. How much is too much for those with?
Like disorders. Now orthostatic disorders come in a bunch of different varieties and we're going to talk about those in a moment. But there are a number of people out there that have low blood pressure, right? People that get dizzy when they stand up, people that are feeling chronically fatigued and in some cases, not all those groups can actually
benefit from increasing their sodium
intake. Several episodes ago on the
human Lab podcast. I gave it what, it's just clearly, what we call anak data, which is not even really data is just anecdotal.
Total data of
an individual, who was always feeling hungry, and craving sugar. And based on the fact that they also had low blood pressure. I had them talk to a physician and they got permission to try a little mini experiment on themselves. And so they did and that many experiment was anytime. They felt like
they were craving sugar, or they were feeling a
little light-headed and dizzy, rather than reaching for something with caloric intake. They took a little bit of sea salt, a little pinch of sea salt and put it into some water and drink.
Rank it.
Or in the case of this individual. They would actually take a little sea salt packet, and they would actually just down a sea salt
packet and for them, that provided tremendous relief for
their dizziness, but that of course, was in the context of
somewhat, abnormally, low blood pressure. So I don't think that they are alone in the
fact that many people out there, suffer from a low blood pressure condition. Many people out there suffer from a high blood pressure condition. So know your blood pressure and understand that blood pressure in part is
Regulated by your sodium intake and your sodium
balanced. Why? Well, because of the osmolarity of blood that we talked about before, where if you have a certain concentration of sodium meaning sufficient sodium in your bloodstream,
that will tend to draw water into the bloodstream and essentially the
pipes that are your capillaries arteries and veins will be full. The blood pressure will get up to your head. Whereas
some people, their blood pressure is
low because the osmolarity of their blood is low
and that can have
a number of Downstream consequences. I should also mention, it can be the consequence itself of challenges or even
deficits and kidney function.
But all of these organs are
working together.
So the encouragement here is not necessarily to ingest more sodium is to know your blood pressure and to address whether or not
an increase in sodium intake would actually benefit your blood pressure in a way that could relieve some of the dizziness and other
symptoms of
things, like orthostatic disorders.
But of course, to do that in a safe context and to never play
games with your blood sugar or your blood osmolarity, That Could set your system down a Cascade of negative events.
Let's look at what the
current recommendations are for people that suffer from orthostatic disorders, like orthostatic hypotension into low tension orthostatic hypotension, postural. Tachycardia syndrome. Sometimes referred to as
pots p 0t, s or idiopathic orthostatic, tachycardia
and syncope. These have the you
Incredibly elaborate names.
Those groups are often told to increase
their salt intake in order to combat their symptoms. The
American Society of hypertension recommends, anywhere from 6,000 to 10,000.
These are very high levels.
So this is 6 G to 10 grams of salt per day. Keeping in mind, again, that salt is not the same as sodium. So that equates to about 24 hundred to four
thousand milligrams of sodium per day again. If you want to learn more about
About this and get more of the citations. I'll refer you back to this study on dietary, sodium and health. How much is too much for those with orthostatic tutorials. We will put a link to this in the caption show notes. So
that's not just in the US. The salt recommendations from the Canadian
cardiovascular Society are ten thousand milligrams of salt per day. So four grams of sodium is what that equates to
and on, and on, and on for things
like, pots for these postural syndromes. That result from, or I should say, from these syndromes, that
Involve low blood pressure when people stand up or in certain postures,
so I point out this paper and I point out these higher salt recommendations to emphasize again that context is vital right. That people with high blood pressure
are going to need certain amounts of salt intake, people with
lower blood pressure and maybe with some of these postural orthostatic, syndromes are going to need
higher amounts of salt. And for most people out there,
you're going to need to evaluate how
how much salt intake is going to allow your brain and body to function.
Optimally and there are some fairly straightforward ways to explore that and there's some ways to explore that in the context of what you already know
about thirst and salt appetite, that can make that exploration one in, which it's not going to be a constant wandering around in the dark and where you can figure out what's right for
you for most people. A moderate increase in salt intake, is not going to be detrimental provided that you
consume enough fluids in particular water.
Okay, meaning if you happen to overeat salt, a bit, you will get thirsty.
You will ingest more water and you will excrete the excess sodium.
There is evidence that the body can store sodium in various organs,
that storage of sodium may or may not be a detrimental thing in general excess storage of
sodium in tissues and organs of the brain. And body is not thought to be good for long-term
health. So, eating much more sodium than you
need for long periods of time is indeed bad for
you.
Earlier, I mentioned that salt
and your hunger and thirst for
salt is homeostatic lie
regulated and indeed. That's the case much like temperature is homeostatic, lie regulated.
What that means is if you pay attention to it, if your salt levels are low, you will tend to crave
salt and salty Beverages, and salty foods.
And in most cases, you should probably follow
that craving provided, those, salty Beverages. And salty foods are not bringing
in a lot of other things
or anything. Ideally, that's bad for you. So I think it's fair to say that whether or not you're
vegan vegetarian carnivore omnivore that we should all
try to limit our ingestion, a process foods.
My read of the literature is that sure some processed foods
are acceptable for us.
We're going to kill us out. Right but that for most people in the world eating fewer
processed foods is just going to be a good thing to do.
So following your salt hunger and thirst in most cases is going to be beneficial provided that it's in the context of eating healthy
non-processed foods on whatever backdrop of nutritional and dietary recommendations is right for you. I simply can't tell you what to eat and what not to eat.
Because I acknowledge the
fact that some people
are vegans because of ethical reasons related to animals or some people are vegans because of, you know, reasons related to the climate and the environment. Other people do it for specific health reasons. Likewise. I
know plenty of people that eat meat and avoid vegetables, believe it or not. And I know people that eat both and they do this often
each I should say
all citing literature that supports their particular camp and their particular
View, it's not a territory. I want to get into but
with respect to salt intake and the fact that home that salt intake is homeostatic Lee regulated. It is the case that if you're craving salt, you probably need it. So for those of you that are sweating excessively or even if you're
in a very hot environment and you're not exercising and you're just
losing, you're
losing water and salt from your
system. Remember also that you can be in a very cold
environment. Very cold dry environments often.
Go together, and you can be losing a lot of fluids from your body and you will crave fluids and salt even though it's cold and you're not actually perfect. You noticeably perspiring. So if
you're exercising a lot, if you're a particular cold dry environment or particular hot environment,
you ought to be ingesting sufficient amounts of salt and fluid
a rule of thumb for exercise. Based replenishment of fluid comes from
what I some episodes. Back referred to as the
Galpin equation.
The Galpin equation. I named
it all the after Andy Galpin and I think that is the appropriate attribution
there. Andy Galpin is an exercise physiologist at Cal State Fullerton, I believe. And he's going to be a
podcast guest here, on the Hebron Lab podcast. He's an exceptional muscle physiologist. He also lives in the
Practical realm where he gives recommendations about exercise to
expert athletes, as well as the everyday person.
So the Galpin equation is based on the fact that
That we lose about 125 pounds of water per hour, which can definitely impact our mental capacity, and our physical performance. And the reason that loss of water from our system, impacts mental capacity, and physical performance has a lot to do with, literally the changes in the volume of those cells. The size of those cells, based on how much sodium is contained in or outside those cells and something that I've alluded to
before on the podcast and I'll talk about more
in a moment, which is that
Ron's signal to one another by way of electricity through something called the action potential and that actually requires sodium and potassium and magnesium. So the Galloping equation suggests that we start exercise hydrated with electrolytes, not just with water. So that means water. That has some sodium potassium and
magnesium. They're simple low-cost ways to do that. We'll talk about
and the formula for hydration, the so-called Galpin equation is your body weight.
A in Pounds, divided by 30 equals the ounces of
fluid. You should drink every 15 minutes.
That may turn out to be more fluid than you can comfortably consumed during the activity that you're performing. Now. The Galpin equation is mainly designed for exercise, but I think is actually a very good rule of thumb for any time that you need to engage mental capacity,
not just physical performance.
Your body weight in pounds, divided by 30 equals the amount, the ounces of fluid. You should drink every 15 minutes. Does not
necessarily mean, you have to ingest it every 15 minutes on the dot. And I think
many activities physical activities but also cognitive activities like Zoom meetings or in-person meetings or lecturing or running or cycling are going to make it complicated to ingest the appropriate.
Fluid every 15 minutes on the dot. I'm not going to speak for Andy for dr. Galpin, but
I think he would probably agree that these are averages to shoot for and that unless you're hyper neurotic, the idea is to make sure that you're entering the activity cognitive or physical
sufficiently hydrated.
And that throughout that activity, your hydrating regularly, and it points to the fact that most people are
probably under hydrating.
But not just under hydrating from
the
perspective of not ingesting enough water that they're probably not getting enough electrolytes as well. Sodium, potassium and magnesium.
So I've said to somewhat contradictory things on the one hand. I said, follow your salt appetite, follow your salt thirsty. If you're craving salt in just some salt
until you stop craving the salt, on the other hand.
I've given you this fairly specific recommendation based on the Galpin equation that you should ingest your body.
In Pounds, divided by 30. That's how many ounces
of fluid you should drink every
15 minutes, which I'm guessing for most people. It's going to be more fluid
than they're currently drinking on average. And so how could it be that you can have a recommendation for what's optimal that's different than the amount that you would reflexively drink and it
has to do with the fact that a lot of the hormone
systems like vasopressin antidiuretic. Hormone
other hormones like aldosterone and a lot of the neural and hormonal signals that govern
salt and water balance.
Balance
are fairly slow to kick in. So, for instance, if you eat a fairly salty meal and you sense that salt, you'll
probably, meaning you detected and perceive
it, because the food tastes
salty, you'll probably want to drink a fair amount of fluid with it. Whereas,
if some of the salt is disguised
by other flavor, something that we'll talk about in a few minutes. When we talk about the neural representation of things, like salty, and
sweet. Well, then you might not notice that something salty and then a few minutes or hours.
You're ingesting that meal you might feel very, very tired. You might even wonder whether or
not it's because of some blood sugar effect. Maybe it's a crash in blood sugar. You might think or something else related to that meal or maybe you think it's because of, you
know, some other event in your life, but
actually what you what has happened is, you're dehydrated because you didn't recognize that you needed to drink more
fluids. So I want to acknowledge the
contradiction in the idea that everything is homemade statically regulated and therefore you are aware of what you need.
Need, and the counter-argument that I you need to follow these strict recommendations. It's actually going to be
somewhere in between, and of course, your body and brain can start to adapt to
certain levels of salt intake. There's a now, fairly famous
study. That was done in Germany, which looked at different phases of salt intake. Meaning they had subjects ingest, either 12 grams of salt per day or nine grams per day or six grams per day for Fairly long period.
The time and they collected urine for testing. This was actually a very controlled study. I'm just going to paraphrase from the National Institutes of Health Report on
this study because they did a very nice write-up of it
and they say that you know, a big surprise of these results. Is that, whatever the level of salt that was consumed sodium was stored end released from the subjects bodies in Fairly regular weekly and monthly patterns, meaning people tended to adapt to a
certain level of salt.
At intake, and then led to
a fairly constant
amount of salt retention and
urine fluid excretion. And that's because of the various hormones like aldosterone, which regulates sodium excretion from the kidney and glucocorticoids, which we'll talk about more in a moment, which help regulate metabolism glucocorticoids are released from the adrenal glands, which ride atop the kidneys and there's a very close relationship between the stress system
glucocorticoids and the salt system.
So the
Reason why your salt
appetite isn't a perfect readout of how much salt you should ingest, and why it might be helpful to follow some of these formulas like the Galpin equation, especially if you're engaging in exercise, where you're going to be perspiring, of
course, is that your body will tend to adapt to a certain amount of salt intake overtime. And then your appetite for salt. Won't necessarily be the best
indication of how much salt you should ingest or
avoid.
Before I move on, I want to really reinforce eyes. The fact that inside of the Galpin
equation. There is that mention of every 15 minutes and people have
come back to me again. And again about this thing. I can't
drink that much water. Every 15 minutes. It's too
much volume of fluid in my stomach. I can't run without etcetera. Remember these are
averages. So that's what you want to average around a particular activity. These are not strict recommendations, where a buzzer goes off in every 15 minutes. You have to chug that exact amount of electrolyte containing
solution.
Another key feature of the study that I was referring to before which incidentally was published in the journal of clinical investigation. Is that the body regulates its salt and water balance, not just by excreting sodium, but by retaining a releasing water.
And this is because of the relationship between sodium and water that we were talking about before, and the advantage of this mechanism. They State here, I'm paraphrasing.
Is that the long-term maintenance of body fluids is dependent is not as dependent on external.
Journal
water as once believed, right? What
this system probably evolved to do was to adjust to different levels of sodium, availability in
the environment and that raises a
really key element of
salt and its importance in human history and human evolution and human health. We haven't talked too much about this and there are
several very good books about the history of salt, you know, it's a salt was a, was
a very valuable and heavily sought-after substance throughout much of human history.
So much so that they're actually written reports of people being paid for labor in the form of salt and salt at when it scares, could has been quite expensive in
certain regions of the world, especially regions located further away from the sea.
And a friend of mine
who has Deep Roots within the culinary
Community told me about traveling to to some
somewhat impoverished areas of Europe, some years ago and
Going into homes, where in the middle of the kitchen table, there was a fish, A Salty Fish hanging from a thread above the table and that because of a lack of availability of table salt. The common practice was to take any
food that needed some salt for additional flavoring and actually
rub that food on this. Salty
Fisher's to squeeze the fish, a bit
onto onto the food
substance in order to get salt from it. So, you know, that's a very
Extreme example, nowadays, we kind
of take salt for granted and most of the
discussion out there is about excess salt. But as I'm pointing out that, you know, salt for a long time, has been a very sought-after commodity and one that people really cherished for their health
in the episode that I did on metabolism. I talked about
the relationship between salt and iodine, if you're interested in iodine and whether or not iodized salt or non-iodized salt is best or required. I'd encourage you to listen to that episode.
Which was
about again metabolism. Some people may need more iodine intake.
Some people perhaps do not, some people might even want to ingest things like kelp, some people might not. So please listen to that episode. If you're interested in the iodine aspects of salt, which have direct impact on thyroid hormone and thyroid function, which, of course, relates to metabolism.
Nowadays. There's a lot of interest in and even a kind of proliferation of what I
call fancy salts. So whether or not, you should be ingesting sea, salts or comment whether or not common table.
Wilson will suffice in most cases for what we're discussing here. Common table salt is fine, but I should point out that sea salt often contains other minerals,
which can be very useful and we will do entire episodes on those other minerals. So sea, salt can contain, you know, dozens or more of minerals, some of, which can be quite valuable to our health, others of which are less less important. In only need to be consumed in Trace Amounts,
but you're not going to get many minerals, if any from
Common table salt. And that's why in addition to
the pretty colors and perhaps some people report that they actually taste better. Some of these so-called fancy salts are sea salts. You might want to consume a more advanced form of salt if you will, although I suppose it's actually the more primitive form of salt, if it's actually the one that comes from the ocean. So we've all heard about how excess salt. It's bad for blood pressure damage, the heart, the brain etcetera.
I do want to give some voice to situations, where too little
Alt can actually cause problems and this has everything to do with the nervous
system. So without getting into excessive amounts of detail the kidneys as we talked about before are going to regulate salt and fluid balance, the
adrenal glands, which ride atop the kidneys are going to make glucocorticoids like
aldosterone and those are going to
directly impact things like fluid balance. And in part they do that by regulating how much
craving for and
It's of
salty Solutions. We have
and there's some really nice studies that have looked at so called adrenalectomy. He's now, this is an extreme case and it's typically done in animal models, but it illustrates the role of the adrenals
in salt
preference. Basically, when the
glucocorticoid system, meaning the release of these particular hormones. From the adrenal glands
is eliminated by adrenalectomy
ectomy means removal.
Then the threshold
Old for what's considered too? Salty, really shifts. Okay. So, typically when the adrenals are intact a animal, or a human, will prefer a mildly salty to
moderately salty solution, if given a
choice and that some point, it's so
salty that it just feels aversive just like taking a. Gulp of seawater is almost always a verse of. I can't think of an instance where it's not aversive and actually drinking seawater can kill you because of the high osmolarity of sea water heater.
I really don't want to drink seawater
under conditions where the adrenals are missing animals and humans will tend to prefer a higher
sodium concentration fluid and they will be
willing to tolerate
ingesting very high concentrations of sodium. Now,
that's a very crude
experiment and not one that you want to do. I
promise you but I mention it because it illustrates that very direct relationship between the stress system, which is the
Corticoid
system and the salt craving system. And this actually makes
sense earlier as we were talking about hypovolemic thirst. When there's a loss of blood pressure from usually due to a loss of blood from the body. There's a salt craving in order to bring that blood volume back up because by ingesting salt you bring fluid into the bloodstream, your increasing that blood pressure and you can restore the blood that's lost.
Now, there are many examples where if sodium levels get
too low in the bloodstream, either because
People are ingesting too little salt, or they are ingesting too much water and therefore excreting too much
salt, that it can cause Stress and Anxiety. There's some really nice data that point to the fact that low dietary
sodium can actually exacerbate anxiety in animal models.
And to some extent, there is
evidence for this in humans as well.
And that should not come as a surprise.
The whole
basis for a relationship between the adrenal system, these glucocorticoids things like aldosterone and the craving for sodium is
that the stress system is a generic system designed to
deal with various challenges to the organism to you or to me or to an
animal and those challenges can arrive in many different forms.
They can be an infection. It can be famine. It can be lack of water and so on.
But in general
The stress response is one
of elevated, heart rate elevated, blood pressure,
and an ability to maintain
movement and resistance to that challenge. Okay, I've said this before, but I'll emphasize it again. There's this common misperception that stress makes us sick and indeed of stress last too long. It has a number of negative effects on our health, but more often than not, if we're
pushing pushing pushing. We're studying or taking care of somebody or traveling like crazy. We don't tend to get sick.
Under those conditions, but as soon as we stop, as soon as we reduce our adrenaline output, as soon as we
reduce our glucocorticoid output from our adrenals, then we will get sick. That's a very common occurrence and it's because stress actually activates our immune system in the short term. So I'd like to try and dispel this myth that stress actually suppresses the immune system, at least, not in the short term, or long term stress. It's a different issue. You don't want long-term ongoing stress, especially of several weeks or
more.
Nonetheless, it makes sense that bringing sodium
into the body would be at
least one way that we would be
wired to counteract or to
resist stressors.
Stressors, being the thing is, on the outside, coming at us. So it could be stressful relationship stressful job situation and again infection. And so on.
It's clear from a number of studies, that if sodium levels are too low that our ability to meet stress challenges as in.
Scared now, that doesn't mean to place your sodium intake, cosmically high.
But it does point to the fact that if you're feeling anxious perhaps from low blood pressure, which can
also give symptoms of anxiety as we talked about before,
but even if it's independent of low blood pressure, that slightly increasing sodium
intake. Again, I would encourage people do this, not in the context of processed foods and drinks, but ideally, in the form of maybe a little bit of sea,
salt and water, or salting ones, food a little bit more.
That, that can stabilize blood
pressure, and one's ability to lean into stressors and challenges.
And I say this, because I think that most people assume that adding salt is
always bad. When in fact, that's simply not the case.
There are conditions such as when we are under
stress challenge. When there is a natural craving for more
sodium. And that natural craving for more sodium, is hardwired
into us as a way to meet that challenge.
So, it's hard for me to know whether or
not people.
Out there, especially the listeners of this podcast are getting too much, just enough or too little sodium. So I can't know that I'm shouting into a tunnel here. You have to decide how much sodium you are ingesting.
But I think that there's some for most people, especially people who are not hypertensive. Pre-hypertensive. There's some wiggle room to explore whether more intake of sodium could actually be
beneficial for suppressing. Some of the anxiety responses that they might feel under conditions of stress,
again. More studies need to
To be done is certainly more studies in humans need to be done. But the relationship between stress and sodium intake, and the fact that additional sodium intake may be beneficial. And indeed is naturally, stimulated by stress shouldn't be necessarily
looked at as a pathological event. I know when some people get stressed, they crave
salty foods, that's actually a hardwired biological
phenomenon that you see not just in humans, but in animals because this is a very primitive mechanism, whereby your body is preparing.
To meet any additional challenges and stressors. Now, we can't have a discussion about
sodium without having a discussion
about the other electrolytes, magnesium and potassium.
Magnesium is important enough in an
extensive enough topic that we should probably do an entire episode. Just on magnesium
for purposes of today's discussion. I just will briefly touch on some of the forms of
magnesium that we discussed on the podcast before in different contexts.
I want to emphasize that many people are probably getting enough.
Magnesium in their diet, that they don't need to supplement. Magnesium.
Some people, however opted to
supplement magnesium in ways that can support them.
And there are many different forms of magnesium and just in very brief passing. I'll just say that there is some evidence that you can reduce muscle
soreness from exercise. By ingestion of magnesium. Malate Mal 8ee.
I've talked before about,
Magnesium, three and eight thre no.8 ee, magnesium 3, and
8 for sake of promoting the transition into sleep and for depth of sleep and
perhaps again highlighted, perhaps because right now it's mainly animal studies and ongoing human studies, but the data aren't all in perhaps
magnesium 3 and 8
can be used as a way to support cognitive function and Longevity, that was discussed in the episode with dr. Jack Feldman from UCLA.
Typically magnesium 3 and 8 is taken 30 to 60 minutes before bedtime in order to encourage sleep. You can go to our neural network newsletter and look for the one on sleep and you can see the recommendations or I should say the, the options for that. Because again, you should always check with your physician. Those aren't strict across-the-board recommendations.
And then there are other forms of magnesium, magnesium, bisque glycinate, which is a somewhat of an alternative to three and eight, not known to have cognitive enhancing
effects, but seems at least on
Our with magnesium, 3 and 8 in terms of promoting transition into in depth of sleep. And so on, there are other forms of magnesium, magnesium citrate, which has other functions, actually. Magnesium citrate is, is a fairly effective laxative, not known to promote sleep and things of that sort. So, a lot of different forms of magnesium, and there are still other forms out
there. Many people are not getting
enough magnesium. Many people are. Ok, so that's magnesium.
Any time we're talking about sodium balance. We have to take into
consideration, potassium, because the way that the kidney works, and the way that sodium balance is regulated both in the body, and the brain is that sodium and potassium are working in close concert with one another.
There are a lot of different recommendations about ratios out there and they range widely from 2 to 1 ratio of potassium to sodium.
I've heard it in the other direction to I've heard a
two-to-one, sodium to potassium.
The recommendations vary, one of the sponsors of this podcast, for instance,
element, which I've talked about in this episode. In before the ratio. There is a gram of sodium to 200 milligrams of potassium, 60 milligrams of magnesium. So they are they've opted for a five to one ratio of sodium to potassium.
And of course, many people, opt to make their own hydration, electrolyte
formulas. They'll put sea salt
into some water. Maybe even in jest, a potassium tablet. It all depends on the context and important contextual
element.
Is your diet.
So, for instance,
carbohydrates, hold water in the body. So regardless of how much salt and how much fluid you're ingesting. If you're ingesting carbohydrate and you
drink fluids water. Some of that fluid is going to be retained in the body. Now, for people that are following
low-carbohydrate diets. One of the most immediate effects of a low carbohydrate diet is that you're going to excrete more water. And so under those conditions. You're also going to lose just water but you'll probably also lose sodium and potassium. And so,
Some people, many people. In fact, find that when they are in a
lower or low-carbohydrate diet than they need to make sure that they're getting enough, sodium and enough potassium. And some people do that, by taking 99 milligrams,
potassium, tablets, every time they eat. Some people do
that by ingesting more foods that contain potassium. And of course, some people who are on low carbohydrate diets doing just vegetables, you know, or other forms of food that carry along with them potassium,
so, it's quite
White variable from person to person. I mean, you can imagine if carbohydrate holds water, water,
and salt, balance and potassium, go hand in hand and hand. That if you're on a low carbohydrate diet that you might need to adjust your salt intake and
potassium and conversely that if you're on a carbohydrate Rich diet or a moderate carbohydrate
diet, then you may need to ingest less sodium and less potassium. And in
fact a certain amount of water is probably coming in
through the foods you eat as well.
So I don't say all this to confuse you again. I say this because
It all depends on the context.
I'll give you yet. Another context that I think is fairly common
nowadays, which is
many people are following a pattern of eating that more or
less resembles intermittent fasting, or at least time restricted feeding. So they're eating fruit between particular feeding windows. And then in the
certain parts of the 24-hour cycle, not
just sleep, but during certain parts of their waking cycle. They're also actively avoiding
food banking on. I
think either the possible I want to se
Oil longevity promoting effects of intermittent
fasting or, and or I should say,
they are banking on the fact that for many people not eating is easier than portion control for certain parts of the day. And so they find it beneficial to limit calories, overall, to a given amount depending on what their goals are, by not consuming food for certain
periods of the day, but usually, during those periods of the day, they're consuming fluids.
And oftentimes those fluids include not just water, but caffeine and caffeine is a diuretic.
It actually causes the excretion of fluids from the body in part because it causes the excretion of
sodium.
All of that to say that if you're somebody who for
instance, eats your first meal around noon or 1:00 or 2:00 p.m. In your fasting, for the early part of the day and you're drinking coffee or tea or an or ingesting, a lot of water. You are
going to be excreting
sodium, along with that water. And so many
people including myself, find that it's useful, especially when I'm drinking caffeine during that so-called fasting
or, you know, non food intake part of the time, restricted,
feeding that, I'm making sure to get enough.
Salt either in the form of something
like element, what
you're like drink or putting some sea salt into some
water or certainly. Any time one is ingesting caffeine replacing,
some of the Lost Water by increasing ones, water intake.
There are some simple rules of thumb around this
that I think can get most people into a place where they're
more comfortable and functioning better, which is for every ounce of coffee or tea that you drink. I should say, caffeinated coffee or tea, that you drink that.
You consume one and a half times as much water. So let's
say you have, you know, an 8 ounce coffee, you know, try and drink about, you don't have to be exact but trying drinking about a 12 ounce glass of water. And you might want to put a tiny bit of sodium into that by tiny bit. I just mean a tiny pinch of sodium because remember,
even if we're talking about increasing the amount of sodium intake
overall, the total amount of sodium contained in salt is
sufficiently high that
even just, you know, a quarter teaspoon is going to really start to move that number up towards that range.
That's still within the safe range. But you're going to if you keep doing that all day long, you're very quickly going to get into that excessive salt intake range, that is deleterious for
health. So again, if you're consuming more caffeine, you're going to be excreting water and salt and potassium. And
so you're going to have to find ways to bring water salt and potassium back in. Again. This has to be evaluated for each of your own individual situations. If you're exercising,
fasted, and you're doing that, after drinking caffeine, then
before during, and certainly after
Exercise, you're going to want to replenish the fluids and electrolytes that you lost including sodium. So
you can imagine how this all starts to become
pretty dizzying and yet it doesn't have to be dizzy. We can
provide some useful
ranges that for most people will work. And so let's talk about what those ranges are. And I'm going to point you to a resource that explores what those ranges are in these various context of nutrition exercise. And so, on
the resource is a book that was authored by dr. James d. Nickel Antonio. He's not a medical doctor.
He's a scientist sighs, cardiovascular
physiology as well. I believe is a doctor of Pharmacy and the title of the book is the salt fix this all, fix is an interesting read because it points to first of all, the
history of salt in society, and as it relates to health,
it actually emphasizes some of the major missteps,
maybe even pretty drastic errors that have been made in terms of trying to interpret the role that salt has in various.
Diseases and emphasizes some of the ways in which perhaps increasing salt can actually improve health outcomes. And I think it strikes a pretty nice balance between what's commonly known about salt and what I believe ought to be known about
salt or at least taken into consideration.
The book does provide certain recommendations, and I actually reach out to the
author. I've never met him in person or talk to him directly, and I asked him.
Outright I said, how much
salt do you recommend? People take on average and
he gave, of course, the appropriate,
caveats about prehypertension hypertension etcetera,
but made a recommendation, which I'll just share with you. And
if you want to learn more about the support for this recommendation, you can check out his book.
The the recommendation he made was anywhere from 8 to 12 grams of salt a day, which corresponds to three point two to
four point eight.
Eight grams of sodium.
So going back to
the current recommendations that we talked about before 2.3 grams of sodium per day.
This is about one and a half times to, you know, double
the amount of sodium that's currently recommended in most circles.
And then what this corresponds to is about one and a half to two teaspoons of salt
per day to arrive at three point, two to four point eight grams of sodium. Again, this is the recommendation that was passed along.
Were most people most conditions barring, you know, specific health health issues.
Now, what was also interesting as he pointed to a sodium to potassium
ratio, which
is four grams of
potassium and he also mentioned 400 mg of magnesium and pointed out. And I generally agree here that many people are deficient in magnesium.
So again, that was a three point, two to four point eight grams of sodium, four grams of potassium. You might think, well, gosh, that's one and a half.
22 times the current recommendation, but we can go back to that study that was mentioned earlier in the episode that 2011 study where I
described this sort of j-shaped
curve in which when you look at the occurrence of these negative health events,
they were fairly low at
low, sodium intake, lower still at slightly higher
sodium intake, much in line with the recommendations that are made or that Dr. Dee nickel Antonio passed along
to me.
And then they increase Christ. Those health risks increased quite substantially as
one moves out past, you know, 6 grams of sodium 7 grams of sodium per day. That's when things really do seem to get hazardous and really, it makes sense. I think given that consensus around this to really avoid very high salt intake.
So the salt fix describes the rationale behind those recommendations. The solve fix also describes in in quite beautiful.
Tail, the relationship between
salt intake, potassium intake, and the relationship to the sugar consumption system.
I'd like to pick up on this idea of the relationship between salt and sugar because I think that one key aspect of the way that salt can work and can benefit us or can harm us has to do with the way that sodium and sugar are regulated and
actually perceived by the brain and how under conditions of certain levels of sodium intake. We
Inspired to seek more sugar or to crave sweets, more or less.
So up. Until now, we've been talking about salt as a
substance and a way to regulate
fluid balance and blood volume. And so on, we haven't talked a lot about
salt as a taste or the taste of things that are salty. And yet we know that we
have salt receptors,
meaning neurons that fire Action, potentials when salty substances are detected much in the same way that we have sweet, detectors and bitter detectors and we
Have Detectors of mommy, the Savory flavor on our tongue
and earlier. At the beginning of the episode. I talked about the fact that we have sweet receptors neurons that respond to the presence of sugar or even non-caloric sweet
things in the gut. And that signals up to the brain through the vagus nerve and those signals Converge on Pathways that relate to dopamine. And so on. Well, we also
have salt sensors at various
locations throughout our digestive tract,
although that the sensation and the taste
Salt actually exerts a very robust effect on certain areas of the brain that can either make us crave more or Sate meaning, fulfill our desire for salt and you can imagine why this would be important. Your brain actually has to register whether or not you're bringing in salt in order to know whether or not you are going to crave salt, more or not,
and beautiful work that's been done by the sucker
lab, Zu, keer. Soaker Lab at Columbia
University as well as
Any other labs have used Imaging techniques and other
techniques, such as molecular biology to Define. These
so-called parallel Pathways parallel, meaning Pathways that
represent sweet or the presence of sweet taste in the mouth and gut, parallel. Pathways meaning neural circuits, that represent the presence of salty taste in the mouth and
gut and so on, and that those go into the brain, move up through brain stem centers, and up to the neocortex in need, where our seed of our conscious perception is to give us a sense, and a
Sharon of the components
of the foods that you happen to be ingesting and a
sense and a perception
of the fluids. And the components of those fluids that we happen to be ingesting.
Now, parallel
Pathways, as I'm describing them are a fundamental feature of every sensory system. Not just the taste system, but also the visual system, we have parallel Pathways for perceiving dark objects versus light objects for perceiving red versus green
Etc. This is a fundamental feature of how we are built and how
Our nervous system works and in The Taste system, much like in these other systems. These pathways are indeed parallel, but they converge in, they can influence one
another. And I
think the simplest way to put this is in the context. First of the visual system, whereby your ability to detect. The color red has everything to do with the fact that you have neurons in your eye that
absorb long wavelengths of light that we call Red's red wavelengths of Light which are longer wavelengths than say blue.
Light to Shorter
wavelength but it is really the comparison
of the electrical activity of the neurons that absorbs red
light with the activity of the neurons that absorb green light, which actually gives you the
perception of red.
So that might seem a little counterintuitive. It but indeed it's not it's actually because something is red and has less greenness that we perceive it as more
red than the green and this is actually
the way that your entire nervous system works. Is that we aren't really
Good at evaluating absolute
levels of anything in the context of perception. It's only by comparison. And actually there's a fun experiment that you can do. I think you could probably find it easily online. You could also do this experiment at home. You can stare at something that's red or green for that matter for a while. So you make an active decision to not blink and to stare at something that's red and then you
look away from that thing. And you'll actually see a
green afterimage of that red object, conversely. If you look at something,
That's green for a while and you stare at and you look away. You'll you will see the red after image of that thing.
Now The Taste system doesn't have quite the same after taste type effect, but nonetheless the pathways the parallel Pathways for salty in the parallel Pathways for sweet and bitter and so on can actually interact. And this has important relevance in the context of food
choices, and sugar
craving. One of the things that's
commonplace nowadays is
in many processed foods.
Foods. There is a business, literally, a business of putting so-called hidden sugars. And these hidden sugars are not always in the form of caloric sugars, that are sometimes in the form of artificial sweeteners into various foods. And you
might say, well, why would they
put more sugar into a
food and then disguise the sugary taste given that sweet taste often compel people to eat more of these things.
Well, it's a way actually of bypassing, some of the homeostatic
mechanisms for sweet, you know, even though we might think that the more
If we eat the more sweet stuff
We crave in general, people have a
threshold where by they say, okay, I've had enough sugary stuff. You can actually experience this if you ever feel
like something is really, really sweet. Take a little sip of water with a little bit of lemon juice in it or vinegar and it will quickly quench that overly
Sweet Sensation or perception. It will disappear almost immediately. There's actually a practice in fancy meals of
a cleansing the
palate through the ingestion of different foods, and that's the same idea that you're cleansing. The polygraph.
Ashley neutralizing, the previous taste. So then they can bring yet another dish to over indulge you in decadence and so forth. So these sensory systems interact in this
way by putting sugars into foods and hiding the sugary Taste of those Foods. Those Foods, even if they contain artificial sweeteners, can
activate the sorts of neurons that we talked about at the beginning of the episode, like the neuro pod cells that will then signal to the brain to release more dopamine and make you crave more of that food.
Whereas had you been able to perceive the true sweetness of that food, you
might have consumed less and indeed. That's what
happens. So these hidden sugars are kind of diabolical. Why am I talking about all of
this in the context of an episode on
salt? Well as many of you have probably noticed a lot of foods
out there contain a salty, sweet combination and it is that combination of salty and sweet which can actually lead you to consume more of the salty. Sweet.
Eat food, then you would have it if it had just been sweet or it had just been salty and that's
because both sweet taste
and salty. Taste have a homeostatic balance. So if you ingest
something that's very, very salty. Pretty soon. Your appetite for
salty foods will be reduced. But if you mask some of that with
sweet well because of the
interactions of these parallel Pathways you somewhat shut down your perception of how much salt, you're ingesting or conversely by ingesting some
V with sweet Foods, you mask, some of the sweetness of the sweet
foods that you're tasting and you will continue to indulge in those
Foods. So salty, sweet interactions can be very diabolical. They can
also be very tasty but they
can be very diabolical. In
terms of inspiring you to eat more of a particular food than you
would. Otherwise. If you were just following
your homeostatic salt or your
homeostatic sugar balance systems and the Beautiful Imaging work. That's been done by the Zucker lab, and other labs has actually been able to reveal how some of this
might
I work by showing for instance that a
certain Ensemble, meaning a certain group of neurons is activated by a sweet taste and a
non-overlapping distinct set of neurons just nearby sitting, you know cheek to jowl with those other neurons would be activated by salty taste and yet others by bitter taste etcetera. So there's a separate map of each different parallel Pathways, but that when
Foods or fluids are ingested, that are both salty and sweet, you get a yet entirely different.
Ensemble of neurons
activated. So your brain, whether or not, it's for your visual system, or your auditory system, or your taste system, has a way of representing the pure form
of taste, salty, Sweet Bitter, Etc. And has a way of representing their combinations and
food manufacturers
have exploited this to large degree.
I mention all of this because if you're somebody who's looking to explore either increasing or decreasing, your sodium intake for health benefits for performance benefits.
In many ways it is useful to do that in the context of a fairly pure. Meaning, unprocessed food, intake
background, whether or not that's keto. Carnivore omnivore, intermittent, fasting, or what have you. It doesn't really matter,
but the closer that foods are to their basic form. And taste meaning not calm, large
combinations of large amounts of ingredients. And certainly avoiding highly
processed foods. The more quickly, you're going to be able to hone in on your
specific.
Salt, appetite and salt needs which has ever pointed
out. Numerous times throughout this episode are going to vary from person to person depending on nutrition, depending on activity, depending on hormone
status, or even portion of your menstrual cycle for that matter.
So, if you want to home in on the appropriate amount of sodium for you, yes, blood pressure is going to be an
important metric to pay attention to as you go along and the parameters for healthy blood. Pressure, ranges are readily available online. So I'll let you refer to those in order to determine those for
yourself but in
Permitting whether or not increasing your salt intake might be beneficial for for instance, for reducing anxiety, a bit or for increasing blood pressure to offset some of these
postural syndromes where you get dizzy at cetera for improving Sports
Performance or cognitive performance.
I can only recommend that you do this in a fairly clean context where you're not trying to do this
by ingesting a bunch of salty foods or salty sweet Foods Etc.
And indeed many people find and it's a reviewed a bit and some of the data are reviewed in the book, The Salt fix that when people increase their salt intake, in a backdrop of relatively, unprocessed foods that Sugar Cravings can
indeed be vastly reduced. And that makes sense given the way that these neural Pathways for salty and sweet.
Interact. Now, thus far, I've already covered quite a lot of material but I would be completely remiss if I didn't emphasize the crucial role. That sodium plays in the way that neurons function. In fact, sodium is one of the key elements that allows neurons
to function at all.
And that's by way of engaging, what we
call the action potential,
the action potential is the firing of
electrical activity by neurons
neurons can.
Engage electrical activity in a number of different ways. They have graded, potentials. They have Gap Junctions. There's a whole landscape of different
electrophysiology is of neurons that
I don't want to go into
just yet at least not in this episode, but the action potential is
the fundamental way in which neurons communicate with one another, they're sometimes called spikes. It's
just kind of nomenclature that neuroscientist use.
I'm just going to briefly describe the
action potential and the role that sodium plays.
And this will involve a
little bit of chemistry, but I
promise, it will be accessible to anyone. Even if you don't have a chemistry or physics, background or electrophysiology background
neurons, have an inside, and an outside and inside are things like the, your genetic
material. They have a bunch of
things floating around in there that allow those cells to function. And they tend to have this wire extending out of them. Sometimes a very long wire. Sometimes a short one that we call the axon, and at the end of that wire.
That
axon, they release little packets of chemicals that either cause the next neuron to fire Action, potentials, or prevent the next
neuron from firing Action, potentials, so they can vomit out these little packets
of chemicals that
either Inspire or suppress Action. Potentials in other neurons.
The way that that whole process occurs is that a given neuron needs to change its electrical activity. So normally neurons are
hanging out and they have what we call a negative charge. And they reason they have a negative charge is that the inside
of the cell has things floating around in it, like potassium a little bit of sodium and some stuff like chloride. These are literally just just imagine these as little little balls of stuff and if they have a
Negative charge on them than the inside of the cell is going to tend to be more negative and outside of the cell. It turns out you're going to have
a bunch of stuff that's positively charged and one of the main factors in creating that positive charge is sodium, sodium carries a positive charge. So you have neurons that
you can just imagine
a for sake of this discussion. You can just imagine as a sphere with a wire sticking out of it. They can put
a little - on the inside for - you can put a little Plus on the
side for positive and when that neuron is stimulated by another neuron,
if the stimulation, the electrical stimulation is sufficiently high.
Meaning enough little packets of neurotransmitter have been vomited onto its
surface. At sufficient concentration. What happens is little pores little spaces, little gaps, open up in the membrane
of that cell, that separates the inside from the outside. And because
it's positive, there's a lot of positive charge outside and there's a lot of negative inside. It's like a Boulder Running downhill.
All the stuff tends to rush, downhill it tries to
create even amounts of
charge. So it's negative on the inside, positive on the outside. And what
happens is sodium rushes into the cell carrying a lot of
charge into the cell. And as a consequence, the charge of that cell goes from negative actually very negative to quite
positive. And if it hits a certain threshold of positive charge because of all the sodium ions going into the cell, then
it fires what's called an action potential.
And it vomits out its own
set of chemicals on to the next neuron. And so it sets off a chain of one. Neuron goes from negative positive Place, vomits out chemicals, under the next one, the
next one, the next neuron that binds to receptors or enters the cell
and that cell goes from negative to positive, charge vomits its contents onto the next one and so on and so
forth.
Sodium rushing into the cell. Therefore
is the way that the
action potential is stimulated. In other words, sodium is the way that neurons communicate with one another. Now the neurons don't stay in a positive
charge. Otherwise, they would just keep vomiting out their contents,
but they need to maintain some of that and they need to go back
to preparing to do it the next time in the next time by resting a bit and turns out that the way they restore
their charge is by pushing that.
Sodium back out of the cell. There are mechanisms in place to do that things like the so called. Sodium
potassium pump. There's a change in the levels of potassium across the cell
membrane and so on and so forth. If you want to look at a demonstration of this you can just you know, you can put into a web browser the app, you know, the action potential you'll find some beautiful descriptions there and YouTube and elsewhere. Maybe sometime on Instagram. I'll do a description with a diagram because I realize number of people are just listening to this. I can't do that here.
I won't do that here because I want everyone to be able to get the same amount of material regardless of whether or not they're watching and or listening to this.
But the point I'd like to make
at least as it relates to this episode on salt, is that
having sufficient levels of
salt. In your system, allows your brain to function allows your nervous system to function at all. Again. This is the most basic aspect of nervous system function.
And there are cases where this whole system gets disrupted and that brings us to the topic.
Goes sodium and water balance.
Its many of you have probably heard but hopefully if you haven't, you'll take this message. Seriously, if you
drink too much water, especially in a short amount of time, you can actually kill
yourself, right? And we certainly don't want that to happen. If you ingest a lot of water in a very short period of time, something called hypernatremia.
You will excrete a lot of sodium very quickly and your ability to regulate kidney function will be disrupted. But in addition to that, your brain
can actually stop functioning. So people have actually consumed water to excess,
especially after sports events and so forth. And if that water doesn't contain
sufficient electrolytes, you can actually shut down neurons ability to function at all by disrupting this balance of sodium and potassium, and the amount of extracellular sodium and neurons ability.
To signal to one another through action, potentials. And I can't emphasize the importance of action. Potentials enough. They are the way that I can lift my pen right now. They're the way that I can speak their the way that you breathe. They literally control all aspects of your nervous system function. Now, it takes
quite a lot of water
intake before you excrete enough sodium that your nervous system is going to shut down. And I certainly don't want to give the impression that simply by ingesting more sodium, your neurons will work better, but it absolutely is the case that if you don't ingest enough sodium that your neurons
I won't function as well as they could and that if your sodium levels are made to Low by Hemorrhage or by
ingesting so much water fluid that you excrete
excess amounts of sodium or through any other mechanism that is then indeed. Your neurons won't be able to fire Action, potentials in your brain and nervous system simply won't
work. And that's one of the primary
reasons why dehydration leads to confusion and dizziness and lack of coordination. And I
About this a bit in the episode on endurance, but
there are instances
in which, you know, competitive athletes have come
into the stadium, to finish a
final lap of a long endurance race and are completely disoriented and actually can't find their way to the Finish Line, you know, it might sound like an of a silly kind of crazy example, but there are examples of people having severe mental issues and physical issues, post exercise. When that exercise involved a ton of sweating or hot environments or insufficient ingestion of fluids and electrolytes because it
Included in an electrolyte formula, of course is sodium. And as you just learned sodium is absolutely crucial for neurons to function. So, to briefly recap, some of what I've talked about today. We talked about how the brain monitors, the amount of salt in your brain
and body and how that relates to thirst,
and the drive to consume more fluid and or salty fluids. We also
talked a little bit about the hormones that come from the brain and operate at the level of the kidney
in order to either retain
or
Allow water to leave your system.
Talked a little bit about the function of the kidney itself. A beautiful organ. We talked about
the relationship between salt intake, and various Health parameters,
and how, a
particular range of salt intake might be optimal, depending on the context in which that range is being consumed. Meaning depending on
whether or not you're hypertensive, pre-hypertensive
or normal tension. We talked about fluid intake and
Your light intake. So sodium, potassium and magnesium in the
context of
athletic or Sports Performance. But also in terms of maintaining cognitive
function, talk about the Galpin equation, which you can easily adapt to your body weight into your circumstances, of course, adjusting the amount of fluid and electrolyte in take upwards. If you're exercising or working in very hot environments downwards, maybe if you're in
less
hot environments where you're sweating less and so on.
We also talked about the relationship between the
Dress system, and the salt craving system, and why those two systems interact. And why, for some people who may suffer a bit from anxiety
or under conditions of stress, increasing salt intake, provided it's done through. Healthy means might actually be
beneficial. We also talked about conditions in which increasing salt intake might be
beneficial for offsetting low blood pressure.
And some of these postural syndromes that can
lead people to dizziness and so forth.
These are things that
Have to be
explored on an individual basis and of course, have to be explored with the support of your doctor.
I mentioned the salt fix, which I think is an interesting read keeping in mind that a lot of the information in their runs counter, to the typical narrative that you hear around Salt. But nonetheless has some
very interesting points that you might want to consider and certainly will broaden your view of the history of and the applications of salt as it relates to a great number of health and performance.
Metrics. We also talked about the
Of
salt, meaning the perception of salty, taste and how the perception of salty taste, and the perception of other tastes like sweet. Can interact with one another to drive. Things like increased sugar
intake, when you're not even aware of it.
And indeed how the combination of salty and sweet taste can bias you towards craving more, for instance,
processed foods and why that might be a good thing to
avoid and of course, we talked about salt and it's critical role in the action potential. The fundamental way in which the nervous
system functions.
At all,
so my hope for you and listening to this episode is that you consider a question and that question is what salt intake is best for you and that you place that question in the context of your fluid intake, you place that in the context of the diet, you're following. The amount of caffeine, you might be ingesting. And the diuretic effects of caffeine and crucially that you place that in the context of the electrolytes, more
generally meaning, sodium potassium.
And magnesium
someday, there will be an online program or an app. I imagine where one could put a bunch of different parameters
in about, you know, their particular health status, their particular diet, their particular exercise, Etc. Maybe it would all be run by AI algorithm or something where it would monitor. All of that for us
and then it would spit out for us. A precise amount of sodium that we
should take in each day.
Unfortunately, no, such tool or device exists right now. And so
So, all of us have to figure out the
appropriate amount of sodium intake for ourselves and that has to be done in these, under these, contextual considerations.
Who knows? Maybe one of you will
Design such an app or such a device. I think it would be very
useful. If nothing else. Today's discussion ought to illuminate. The fact that some strict recommendation of salt intake. Cannot be made
universally across the board for everybody. There's just simply no way that could be, that could be done.
And yet I think most of what we've learned
about salt in the general discussions around Health are that it's this evil substance.
Nothing could be further from the truth. It's an incredible substance. Our physiology is dependent on it. Our cognition is
depend on dependent on it, indeed our mental and physical health, and our performance in essentially, all aspects of life is dependent on it.
And I hope I've been able to illuminate some of the beautiful ways in
which the brain and the bodily organs interact in order to help us regulate this.
That we call sodium balance. And the
fact that we have neurons in our brain that are both tuned to the levels of salt
in our body and
position in a location. And in the brain that allows them
to detect the levels of salt in our body and to drive the intake of more or less salt and more or less fluid and other
electrolytes, really just points to the beauty of the system that
we've all evolved
that allows us to interact with our environment and make adjustments, according to the
context of our daily and ongoing life
if you're learning.
Enter enjoying this podcast, please subscribe to our YouTube channel. That's a terrific. Zero cost way to support us. In addition, please subscribe to the podcast on Spotify and or
apple.
And on Apple, you have the opportunity to leave us up to a
five star review, and you can also leave us a comment,
the best place to leave us comments. However, is on the YouTube channel, they are. You can make suggestions about future podcast guessed that you'd like us to interview a
future podcast topics that you'd like us to
cover. And of course, you can give us feedback about the content of this.
Or other
podcast, we do read all those comments,
please. Also check out our sponsors mentioned at the beginning of today's episode. That's the best way to
support this podcast. We also have a
patreon. It's patreon.com slash Andrew hubermann and there you can support the
podcast at any level that you like
during today's episode and on many previous episodes of The
huberman Lab podcast, we discussed supplements while
supplements aren't necessary for everybody. Many people drive tremendous benefit from
them for things like enhancing sleep and focus and so on.
One issue with supplements. However, is that the quality of supplements varies tremendously
from one brand to the next for
that reason, we've partnered with Thorn, th OU are any because Thorn supplements are of the absolute highest quality. In terms of the ingredients. They include and the Precision of the amounts
of the ingredients. They include meaning. What's
listed on the bottle
is, what's actually contained in that product. They partnered with all the major sports teams. And with the Mayo Clinic,
so trust is very, very
high with respect to the quality of thorn products
if you'd like to see the thorns
Moments that I take, you can go to Thorn that's th are any on.com slash the letter U / huberman and you can get 20% off any of those sore and
supplements. In addition. If you navigate deeper into the thorn site through that portal, Thorn.com / you /
hubermann, you can also get 20% off any
of the other supplements that thorn makes.
If you're not already following huberman lab on Instagram and Twitter, and please do so there. I cover science and science based tools that sometimes overlaps with the content of this podcast.
Cast. But sometimes is distinct
from the content of this podcast.
We also have a neural network newsletter. The neural network newsletter comes out once a month. It is zero cost you signed up for it by providing your email. We do not share your email with anybody. The privacy policy is made very clear and you can sign up for the neural network newsletter by going to huberman lab.com. Just going to the menu, scroll down to neural network and you can sign up. And even without signing up, you can access some of the
previous newsletters if you'd like to see what they are. Like we include short.
He's from podcasts and key takeaways and some resources and tools that you won't find anywhere else.
Thank you. Once again for joining me today to discuss the neuroscience and the physiology
around Salt and its many incredible influences on our brain and body. And last but certainly not least. Thank you for your interest in science.
