How to Optimize Your Water Quality & Intake for Health

Andrew Huberman 0:00 (instrumental music) 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're discussing water. Now, to some of you, water might seem like a boring topic, but I assure you that water is anything but a boring topic. In fact, water as a substance is incredibly interesting for a variety of reasons that I'll explain today. In fact, we are going to discuss the physics and chemistry of water, and I promise to make it accessible to anyone and everyone, regardless of whether or not you have a physics or chemistry background. And I will discuss how your body needs and utilizes water depending on what type of water you drink, the temperature of that water, when you drink the water, and indeed how you drink that water. Now, water is actually a pretty controversial topic. In fact, in preparing for this episode, which took me several months in fact, I ran into highly contradictory information and had to go on some real deep dives in order to ferret out the best and most accurate knowledge for you. I also found that there are generally two camps of people out there in terms of how they think about water and the consumption of water. One camp, generally speaking, is of the mind that tap water is completely safe. Perhaps it needs a little bit of filtering, but that in most areas of the world, if it runs out of the tap, and unless there's a warning sign directly above the faucet, that you can drink the tap water. The other camp seems to be the camp that does not trust anything that comes out of the tap and is excited by and in fact relies on things like reverse osmosis, deuterium-depleted, hydrogen-rich, or other forms of water that sometimes can be very expensive or at least involve some substantial steps in order to clean, filter, alter the chemistry of, or in some other way adjust before they are willing to consume it. So today what we're going to try and do is to address all the stances around water. For instance, we will discuss whether or not tap water is indeed safe, and I will give you some tools that will allow you to address whether or not the water coming out of your tap is safe, as well as some tools that will allow you to address how to clean that water if indeed it does need filtering and cleaning, in particular for things like fluorides and endocrine disruptors, which it turns out are quite prominent in a lot, not all, but a lot of tap water sources. I will also talk about the more, quote-unquote, "esoteric" forms of water that I mentioned a few minutes ago. So I will go systematically through the list of distilled, reverse osmosis, spring water, deuterium-depleted water, high pH water. And for those of you that are already screaming out as you hear this, "Oh, no, he's going to tell us that pH water can alter the pH of our body in helpful ways," I'm not going to tell you that. But I will tell you that the alkalinity or acidity of the water, that is the pH of the water that you drink, has a profound impact on your ability to absorb and utilize that water and the impact that those water molecules have on specific biological systems. So it turns out pH is very important, but not for the reasons that you've probably heard about previously. I will talk about how the temperature of water that you drink does indeed turn out to be important for the rate of absorption of that water and its impact on the cells, tissues, and organs of your body, and thereby your health, and I will talk about various zero-cost and low-cost tools that you can use in order to get the most out of the water that you drink. And finally, I will talk about when and how to hydrate your body best. Before

Andrew Huberman 3:33 we dive into today's topic, I want to share with you some very interesting results that were just published on the use of deliberate cold exposure to benefit fat loss. Now, deliberate cold exposure is a topic I've covered before on this podcast. We have an entire episode about that that I've linked in the show note captions. Deliberate cold exposure can be done by way of cold showers or immersion in cold or ice water up to the neck. That's typically, uh, the ways that it's done. It has been shown to reduce inflammation, to increase metabolism, and I think some of the most exciting results that have been published are the results, certainly in humans, showing that deliberate cold exposure can increase the release of so-called catecholamines, which are dopamine, norepinephrine, and epinephrine, and those increases in those three molecules are quite long-lasting and lead to substantial increases in mood and focus throughout the day. Now, many people out there hear about deliberate cold exposure and cringe. Other people hear about it and cringe because they've heard that deliberate cold exposure, especially by way of immersion in water, can block the adaptation to strength or hypertrophy training. What I mean by that is, yes indeed, there are data showing that if one gets into very cold water up to the neck, in the six hours, any time, that is, in the six hours after strength or hypertrophy training, that some of the strength and hypertrophy increases that one would observe are blocked by that deliberate cold exposure. However, after six hours does not seem to be a problem, so it can be done on o- other days besides the strength and hypertrophy training. It can be done before strength and hypertrophy training, it can be done after endurance work! And I should mention that it does not appear that cold showers disrupt the adaptations to strength and hypertrophy training even if they are done immediately after strength or hypertrophy training. Okay, with that said, many people do enjoy the effects of deliberate cold exposure, in particular for those increases in mood and alertness that are the consequence of those increases in the catecholamines dopamine, norepinephrine, and epinephrine. And again, those increases are very long-lasting, so it's not just during the exposure to cold, it is for several hours, up to four, maybe even five or six hours depending on how cold and how long the deliberate cold exposure happens to be. Again, there's a lot to say and explore about deliberate cold exposure, so again, I'll just refer you to the episode on deliberate cold exposure if you want to explore the mechanisms and the positive health outcomes, some of the controversies within the data, et cetera, within that episode. Meanwhile, I definitely want to share with you the results of this recent study...... that just came out. The title of this study is Impact of Cold Exposure on Life Satisfaction and Physical Composition of Soldiers. And the reason this study is very interesting is that it's one of the few studies that used, or I should say explored both deliberate cold exposure by immersion in cold water as well as deliberate cold exposure by way of cold showers as it relates to weight loss. Now, there's already data out there on the effects of deliberate cold exposure and metabolism, and here I'm mainly referring to the beautiful work of Dr. Susanna Söberg and colleagues in Scandinavia that showed that people that do 11 minutes total of deliberate cold exposure by immersion in cold water up to the neck per week, so 11 minutes per week total spread out across some different sessions by way of getting into water that's uncomfortably cold up to the neck and then getting out and then doing that several times per week to hit that 11 minutes or more threshold and this is very important, will come up in a moment in the context of this new study, and warming up not by getting into a warm shower, which is frankly what I do after my cold showers, or, uh, getting into the ice bath or cold water immersion, but rather forcing their body to warm up naturally by using its own metabolic abilities. In those studies, they observed substantial increases in brown fat stores, which are fat stores that you really want around the heart and clavicles, increases in metabolism that were quite dramatic in my opinion, and that could be very beneficial for allowing people to feel more comfortable at cold temperatures when they're not in cold water and on and on. So lots of benefits shown in that study. In this study, what I thought was particularly interesting is, again, they explored both immersion in cold water and cold showers and the duration of cold exposure that they found led to substantial fat loss, especially around the abdomen, was very brief deliberate cold exposure. Let me give you a few details about this study. The study involved 49 subjects that include both males and females. This is also really important. The beautiful work of Susanna Söberg and colleagues, as far as I know, only looked at males. This study looked at males and females. They were 19 to 30 years old, and there basically were two groups. People were either were assigned to get deliberate cold exposure or they were, uh, not assigned to deliberate cold exposure. The form of deliberate cold exposure involved one session per week of cold immersion in cold water up to the neck and to just give you a sense of how cold it was, it was three degrees Celsius, which translates to about 37.5 degrees Fahrenheit. That's pretty darn cold, but it was only for two minutes. Okay? So one session at three degrees Celsius, otherwise known as 37.4 degrees Fahrenheit, for two minutes every week, once a week. In addition, the same subjects did five cold showers per week, or a minimum of five cold showers per week, and those cold showers were slightly warmer than the immersion in cold water condition, so they were 10 degrees Celsius approximately or 50 degrees Fahrenheit. Still pretty cold. And the duration of that cold water exposure in the shower was just for 30 seconds. Okay? So this is interesting to me, because many people don't have access to cold water immersion. They might not have an ice bath or any place they can do that, but they d- most people do have access to a cold shower of some sort. Plus I think most people could do probably one ice bath per week or find a place where they could get into cold water safely. Now, I should point out that some people will not do well going into 37.5 degree Fahrenheit, AKA three degree Celsius water having never done anything like this before. So if you're going to try and employ these sorts of protocols that were used in this study, I do recommend that you ease into it over the course of a week or so and become somewhat adapted to the, the shock of cold water exposure. So maybe start at, you know, 50 degrees Fahrenheit, kind of ease your way back in terms of the cold water immersion especially. Now, another critical feature of this study is, as with the beautiful work by Susanna Söberg, the subjects were told to warm up naturally after the deliberate cold exposure. So they basically hung out outside of the cold water immersion or outside of the cold shower for 10 minutes after they were exposed to the cold in their bathing suit or I'm, I'm assuming they were wearing something. Um, but the point is that you are not going from deliberate cold exposure directly into a hot shower or a sauna or something of that sort. So again, their bodies were forced to heat up again naturally after the deliberate cold exposure, but after the 10-minute period, they were able to do whatever they wanted essentially, re-clothe, take a warm shower, and so on and go about their day. Now, the results of this deliberate cold exposure protocol, again, two minutes in cold immersion at three degrees Celsius, 37.5 degrees Fahrenheit, plus five cold showers per week of two minutes long, a little bit warmer, 10 degrees Celsius, 50 degrees Fahrenheit. Now, the deliberate cold exposure used in this study caused many different statistically significant positive changes. They had a very extensive questionnaire that related to mood, everything from levels of anxiety to sexual satisfaction and on and on. In fact, they saw a, uh, s- statistically significant improvement in sexual satisfaction in the subjects that were exposed to deliberate cold exposure, not in the control group. Although they didn't look at this, chances are those improvements in sexual satisfaction were the downstream consequence of the known increases in testosterone and free testosterone that occur in both men and women who do the sorts of deliberate cold exposure, again, testosterone being an important hormone for libido in both men and women. They also saw improvements in regulation of anxiety, which I think is very interesting given that the deliberate cold exposure often causes people anxiety, but here and in other studies we've seen, it can lead to an, uh, better ability to buffer against anxiety in the normal happenings of everyday life.Perhaps the most interesting and significant results that they found in the study however, were that, in particular in men, there was a reduction in waist circumference following eight weeks of this deliberate cold exposure, as well as a 5.5%, on average, 5.5% reduction in abdominal fat that was quite statistically significant when compared to the other groups. Now, why there was no observed reduction in abdominal fat or waist circumference in the female subjects isn't clear. Could have to do with just the way that, uh, body fat is, is stored and metabolized in females versus males. That is going to be a topic for future exploration. So I do think this study is very interesting, because when you look at the landscape of science and discussion around deliberate cold exposure, I think there's a general consensus now that deliberate cold exposure can change one's sense of mood and wellbeing through these increases in catecholamines that I mentioned earlier. But the impact on metabolism itself has been somewhat controversial, because the overall changes in metabolism that are observed, while statistically significant in many studies, have not ever really been shown to translate into weight loss or body fat loss in any kind of specific way. And of course, a great advantage of this study is that by exploring soldiers, they were able to really hold constant a number of other features, like the amount of daily activity that those soldiers are exposed to, their diet, their living conditions, and so on and so forth. So at least insofar as human studies are done, it's a, it's a very well controlled study. We'll provide a link to this study in the show note captions, and for those of you that are thinking about employing the protocol that's used in this, uh, particular paper or combining it with existing deliberate cold exposure protocols, to me it seems pretty straightforward and of pretty minimal time investment. Just two minutes of deliberate cold exposure by way of water immersion up to the neck and five times a week of 30 seconds each of deliberate cold exposure by way of cold shower. And just a quick mention about cold showers, if you're going to use cold showers to do deliberate cold exposure, you're going to want to stand under the shower itself, right? Uh, and essentially have it hit your head, the back of your neck, and your upper back, which is where most of your brown fat stores are concentrated, and it turns out that cold exposure to those regions of the body in particular are going to trigger the adaptation of increased brown fat stores, which involves increases of mitochondria in those fat. Again, this is not the blubbery fat beneath the skin. This is the fat that acts as kind of an oil in the furnace that is, uh, your thermogenic properties of your body to generate heat and burn off so-called white adipose tissue elsewhere in the body. Now, anyone that understands the laws of physics and thermodynamics will be saying, "Wait, in order to get fat loss, you need to have a caloric deficit." Calories in, calories out still applies. And yes, that's absolutely true. We can only conclude on the basis of the results of this study that the people that lost body fat were indeed in a caloric deficit, presumably because all other factors were held more or less constant in this group of soldiers, presumably because the deliberate cold exposure itself elevated metabolism, thereby increasing the calories out component of the calories in, calories out equation, which of course governs the rules of weight loss and body fat loss as well.

Andrew Huberman 15:26 Before we begin, I'd like to emphasize 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 LMNT. LMNT is an electrolyte drink with everything you need and nothing you don't. That means plenty of salt, magnesium, and potassium, the so-called electrolytes, and no sugar. Now, salt, magnesium, and potassium are critical to the function of all the cells in your body, in particular to the function of your nerve cells, also called neurons. In fact, in order for your neurons to function properly, all three electrolytes need to be present in the proper ratios, and we now know that even slight reductions in electrolyte concentrations or dehydration of the body can lead to deficits in cognitive and physical performance. LMNT contains a science-backed electrolyte ratio of 1,000 milligrams, that's one gram, of sodium, 200 milligrams of potassium, and 60 milligrams of magnesium. I typically drink LMNT first thing in the morning when I wake up in order to hydrate my body and make sure I have enough electrolytes and while I do any kind of physical training and after physical training as well, especially if I've been sweating a lot. If you'd like to try LMNT, you can go to Drink LMNT, that's lmnt.com/huberman, to claim a free LMNT sample pack with your purchase. Again, that's Drink LMNT, lmnt.com/huberman. Today's episode is also brought to us by Thesis. Thesis makes custom nootropics. Now, nootropics is a word that I don't like. I don't like it because it means smart drugs. And as a neuroscientist, we know that we have brain circuits for focus, brain circuits that enable creativity, brain circuits that allow task switching, and on and on. So there's really no such thing as a brain circuit for being smart. Now, Thesis understands this and has designed custom nootropics that are designed to get your brain and body into the optimal state for the specific types of work, that is physical or cognitive work, that you want to do. I've been using Thesis for more than a year now, and it's completely changed the way that I approach work. I typically take the Clarity formula prior to doing any kind of cognitive work, and I'll take their Energy formula often before workouts. If you'd like to try your own personalized nootropic starter kit, you can go online to takethesis.com/huberman and take their brief three-minute quiz. That quiz will allow them to send you four different trial formulas that you can use for a month, and then you can iterate with them to find the ideal nootropic formulas for you. Again, that's takethesis.com/huberman and use the code Huberman at checkout to get 10% off your first order.Today's episode is also brought to us by HVMN Ketone IQ. Ketone IQ is a ketone supplement that increases blood ketones. Now, many people have heard of the ketogenic diet, and indeed the ketogenic diet has been useful for many people out there. However, most people out there, including myself, do not follow a ketogenic diet. That is, I eat carbohydrates. However, it's important to note that even if you are not on a ketogenic diet, you can benefit from increasing your blood ketones. In fact, I'll use Ketone IQ after lunch or in the afternoon with some coffee, or sometimes first thing in the morning. If I'm particularly hungry and I want to do exercise or I want to do cognitive work but I want to delay my first meal, using Ketone IQ allows me to curb my hunger and gives me a lot of focus and energy, and that's because ketones are one of the brain's preferred fuels for cognitive work. In fact, ketones have been shown to be associated with forebrain function, which is associated with context switching, focus, and formulations of strategies, et cetera, all the sorts of things that are important for doing deliberate focused work or physical performance. If you'd like to try Ketone IQ, you can go to HVMN.com/huberman to save 20% off your order. Again, that's HVMN.com/huberman. The Huberman Lab Podcast is now partnered with Momentous Supplements. To find the supplements we discuss on the Huberman Lab Podcast, you can go to Live Momentous, spelled O-U-S, livemomentous.com/huberman. And I should just mention that the library of those supplements is constantly expanding. Again, that's livemomentous.com/huberman.

Andrew Huberman 19:27 Let's talk about water, and let's start off by answering the question, what is water? Water is of course H2O. Most everybody knows that from an early age. But what H2O means is that each molecule of water consists of two hydrogens and one oxygen. Now, the physical arrangement of those two hydrogens and one oxygen turns out to be really important for how water functions in the body, and frankly, elsewhere in our world and life. If you were to make a peace symbol, that is to put up your index finger and your middle finger simultaneously, in fact I'm going to recommend you do that now unless you're using your hands for something else important, in which case do it later. Well, if you make that peace symbol and you look at your hand, you have a pretty good impression of what an individual water molecule consists of, which is H2O, two hydrogens and an oxygen. And with that peace symbol, the fingers, or the tips of your fingers rather, are going to represent the hydrogens. Your fingers, that is the length of each of those fingers, is going to represent the electron bonds to the oxygen, and the palm of your hand and the fingers that are down are going to represent the oxygen. Okay? Now, what's important about that visual impression or visual image of the individual water molecule is that it is polarized. That is, the hydrogens over on one side, both of them are over on one side, and the oxygen is over on another. And what's really important about water molecules being polarized is that they can bind to one another by way of that polarization. And this has to do with something that we all kind of learned in chemistry at one point but many of us forgot, maybe we didn't even understand it the first time around, which is that positives and negatives attract. So when you have individual water molecules, they have the opportunity to interact and essentially bind to one another, and they bind through what are called covalent bonds. Covalent bonds are relatively weak bonds, and so as a consequence, water can change its conformation. However, covalent bonds are strong enough that water actually can maintain some structure, and that structure will vary, of course, depending on its temperature. So, what you need to know about water is that indeed it consists of lots of individual H2Os, and those H2Os can arrange themselves in different ways, and that temperature is a strong determinant of the arrangement of those water molecules. That is, they're bonding to one another, and in fact, even their spacing between those bonds. So again, even if you don't have any chemistry, stay with me because you'll definitely understand this. Water can exist in at least three forms and maybe four forms. We know that it can be liquid, of course. That's really w- normally what we think of when we think of water. It can be gas, so we think of steam, right? So if you heat it up it takes on a, uh, not a semi-solid or a semi-liquid form. It takes on this property of steam or gas, okay? So when you see steam or when you, um, breathe on a cold day through your mouth or through your nose and you see your air, those are water molecules that are condensing, that is bonding in certain ways based on differences in temperature between the inside of your body and the outside air. And of course, it can be a solid. It can be ice. Now, ice is fascinating and important in understanding how water works, and this will become relevant later when we think about how water works within the body as well, especially how different temperatures of water impact the health and behavior of our cells. And the most important point to understand about water in its solid state is that unlike most substances, when water is in its solid state it is actually less dense than when it's in its liquid state. So just think about that. Most substances, most metals for instance, when they are in a solid state they are more dense than when they are in a liquid state. So for instance, if they're in a solid state they will sink in a container filled with their liquid form. Not water. Water is very interesting because as you cool water, and water transitions from a liquid to a solid, it still binds. That is, it can form bonds between those different molecules of water, but the spacing between those H2Os, so again those peace symbols with hands, so if you had a bunch of those, so if you had, you know, a thousand hands all making peace symbols, they can bond to one another. But when it's cold, those bonds are actually made further apart from one another, and as a consequence, ice, as we all know, floats in water. In other words, put very simply, water is unusual and special in that in its solid form, ice, it is actually less dense than when it's in its liquid form, and that's why ice floats in water. Now, this is important not just to our, our biology but to all of life, because if you think about it, if it were not the case that water is less dense in its solid form, ice, than it is in its liquid form-... the bottoms of our oceans would be covered with thick sheets of ice. And if that were the case, you can be absolutely sure that life would not exist on our planet the way that it does, and there's a good chance that we would not exist as a species because so much of what allows us to exist on thi- this planet and the other animals to exist on this planet relies on photosynthesis pathways and plants that are dependent on the sun and interactions with the oceans and lakes and other bodies of water. And of course, the ice caps are vitally important, that is, the presence of ice, especially at the poles but elsewhere in bodies of water as well. So icebergs are a critical part of the ecosystem that allows for everything from photosynthesis to the ability of certain animals to extract food from each other and from their local resources. Now, there's a whole discussion to be had there, but the important point for now is that the physical properties of the bonds between water that are made and changed depending on temperature turn out to be essential for us to be present on this planet at all and for our cells to function in the ways that they do for sake of health and for sake of disease. And we'll explore this later when we talk about the critical relationship between temperature, pH, which is the relationship between alkalinity, how basic, or acidity, how acid a given liquid, or in this case we're going to be talking about water, is, and the ways that our cells can or can't use water. So I realize that this is, uh, fairly in-depth for those of you that don't have much of a background in chemistry. I've tried to keep it really top contour, but if you can make a peace symbol or if you can just imagine a peace symbol in your mind and realize that that's a water molecule and that those water molecules can bind to one another through bonds that are relatively strong but weak enough that they can be broken if they need to and that the temperature that those water molecules are exposed to changes the distance between those bonds and that's what allows ice to float in water, then you're going to have no problem with the remainder of the discussion today. In fact,

Andrew Huberman 26:33 you will also have the ability to understand things that you've observed many times over but perhaps have never thought about or really understood, which are, for instance, that water has a certain level of surface tension. For instance, if you've ever been to the ocean and the waves are coming in, what you'll notice is if you walk on the dry sand or gravel, uh, pebbles that is, of the ocean, it's very easy, right? I mean, the pebbles move down or the sand moves down, it depresses a little bit due to the weight of your body. But as you get closer to the water, you're going to sink deeper because that sand is more saturated with water, but at some point, you won't be able to actually walk on top of the water, right? It has been said that Jesus walked on water, there's the so-called Jesus Christ lizard, so named because it can actually walk on the surface of water. A leaf can float on the surface of water. Under some conditions, a coin can float on the surface of water. If you make coffee in the morning, you can actually take a spoonful of that hot coffee and pour a little bit on the surface of your coffee, and you'll notice that it will bead up and, uh, you'll get little, uh, round spheres of water. Those are little water molecules bound to one another that spin on top of the surface before they sink under. Uh, that has everything to do with the bonding between water that's dependent on temperature but also, as with the difficulty for essentially everybody, uh, to walk on water or for animals to walk on water, the surface tension of water allows certain things to float there or to stay at the surface, but there's a very thin layer of water molecules at the surface of water that are more dense than the water that resides at deeper depths, and that's why most things, including us, sink in water. We are more dense than water. Now, I did mention earlier that there are three forms of water. There's the ones that we all are familiar with, the solid, liquid, and gas forms of water. However, there are data, mainly from Gerald Pollack's laboratory at the University of Washington, that have described the so-called fourth phase of water, which is structured water. And we'll get into this a little bit later because structured water has really been a prominent topic in the, let's call it the, uh, water health aficionados. It's a heavily debated topic as to whether or not structured water is somehow better for our cells if it exists within our bodies. We'll get into that, um, in full detail later. But the whole notion of structured water is that in the presence of certain solids or certain liquids, the conformation of water, that is, the water molecules, actually change somewhat. This has been demonstrated. Whether or not it has relevance to the biological function of our body is a different issue, but we know that there is this fourth phase of water called structured water. Structured water, uh, is a fairly complicated topic, but we can make it very simple for sake of today's discussion. I mentioned earlier that opposite poles attract, that is, positives and negatives attract and typically, um, things that are negatively charged when presented with another negative charge either repel or don't attract. Things that are positively charged in the presence of another positive charge also tend to repel. This is the basis of magnets, um, either, uh, sticking to one another or repelling from one another, and there's also the idea that human beings who are opposites attract, but that's a different episode that we need to do in the future. The point here is that structured water is a unique condition in which the local environment that these water molecules happen to be in allows positive charges between different water molecules to attract one another. So again, whereas normally it's positive and negatives that attract, in the configuration that we call structured water, positives and positives attract and form bonds that are stronger than the typical bonds that would be formed between water molecules. And just as a kind of prelude to our discussion about structured water as it may or may not relate to health later, there are a number of people that believe that within the body because of the presence of certain liquids and solids, that the water within our cells and in particular within the interactions with so-called organelles, organelles are things like mitochondria, um, the Golgi apparatus, they have fancy names, these are the, these are things within cells that allow cells to do everything from make proteins to traffic proteins out to the surface of cells, things like neurotransmitters and receptors and so on. A lot of people who are interested in structured water as it relates to biological function have hypothesized or like to debate rather whether or not in the body water is not just present in its liquid form.... or gaseous form. We know it's not present in its solid form unless you gulp down some ice cubes, for instance. But there is a cohort of people out there, including some fairly accomplished scientists, that believe that within the body, the organelles of our cells act as a substrate for water to exist in this fourth form, this structured water form. And that's led to this whole niche industry of people, um, who are proponents of consuming so-called structured water. And we'll, again, we'll get to that a little bit later. So now you know what individual water molecules consist of. When you hear H2O, hopefully you'll get that, uh, visual image in your mind of an individual water molecule being the peace symbol and a bunch of those binding to one another through these, uh, relatively weak bonds, but strong enough that certain things can take place like surface tension. Um, keep in mind that surface tension of water may relate to either standard bonds between water or this fourth phase, um, that's heavily (laughs) debated still. Um, but we certainly know that, um, for instance, if you were to take a piece of wax paper or glass and you were to pour some water on it, you would notice that the water would bead up or kind of aggregate at particular locations. When you see that beading up or the aggregation of water molecules on a particular surface, you're seeing two things. This is actually, um, kind of fun. The next time you see it, you'll know that the, the aggregation, the beading up of water with itself, so individual water molecules or many water molecules kind of aggregating at one location and making a bead of water, that's due to these bonds, these covalent bonds occurring between water molecules. But also you'll notice that on a vertical pane of glass, say in rain or on your windshield, that the water will look almost like it's sticking to the glass. And that's because there are actually bonds between the water molecules that have beaded up themselves and the glass. So water can not just bind to itself, it can also bind to certain surfaces. And the fact that perhaps if you drive your car, if you were to tap the window or if a big enough bead of water formed on a window that it would start to drip down. And that's because those bonds with the surface are strong, but they're not so strong that it stick at that location. Quite different than water that is in its solid form, ice, that can actually really adhere. If you've ever had to scrape ice off a windshield, so if you, most of you live in, uh, cold regions you're familiar with this, have to scrape ice off a windshield, you realize that the bonds between water in its solid form and different surfaces is quite a bit stronger than the bonds between different water molecules with each other or the bonds between water and different surfaces when they are warmer. Okay? So I do realize that for a lot of people listening, that's going to be a pretty deep dive into the chemistry and physical properties of water, but all you really need to know is that these (laughs) water molecules are incredibly versatile and can bind to each other and can bind to different surfaces and can allow things to float or to sink or even to move across surfaces of water based on the three, perhaps four different, um, states that water can be in. And that versatility that you observe in the natural world on window panes and rain and clouds and hail and ice and snow and scraping ice off your windshield in the cold of winter and perspiration and so on, all of that is fine and good,

Andrew Huberman 34:08 but realize that almost all of those same sorts of properties of water become extremely relevant when thinking about how your body actually utilizes water. And the key thing here is that temperature and the so-called alkalinity or acidity, that is the pH of water, turn out to be very important determinants of how water is used by the cells of your body. In fact, as I'll describe in a moment, we have entire sets of biological mechanisms solely devoted to trying to get water into our cells in very specific ways, including at specific rates and to use water in different ways, because as you've probably heard before, we are mostly water. What's kind of interesting to me and what I found researching this episode is that the percentages of our cells and bodies that are, um, purported to be water is a pretty broad range. Some people say we're 55% water, other people say we're 70% water. Some people say we're 95% water. The exact percentage doesn't matter so much and really just boils down to whether or not the person that's stating that percentage is talking about how much water is present in our cells and body at a given moment, versus how much water was involved in the process of creating the sorts of proteins and other things of our body that are required to have hair cells, skin cells, brain cells, et cetera. So if you really want a number out there, uh, I can't give you a single number. If you want to be accurate, it's going to have to be a range. And basically, we are anywhere from 70% to 90% water depending on how you define being water. That is whether or not you're talking about water being present in cells in its liquid form or maybe in this fourth structured water form if you're, um, of the mind that that exists within us, and whether or not you're talking about water that was used to create a given protein like a receptor or a neurotransmitter, or whether or not you're talking about the water just being water as H2O. Okay? So again, it's very easy to (laughs) go down that rabbit hole, and this is, um, part of the reason why there's such a wide discrepancy of assertions as to how much of us is water, but let's be direct. Most of our body is water, and there isn't a single other molecule in the universe that we can look to and say that it has as important a role in our health and biology and frankly our presence of life on Earth at all

Andrew Huberman 36:22 than water. I'd like to take a quick break and acknowledge one of our sponsors, Athletic Greens. Athletic Greens, now called AG1, is a vitamin mineral probiotic drink that covers all of your foundational nutritional needs. I've been taking Athletic Greens since 2012, so I'm delighted that they're sponsoring the podcast. The reason I started taking Athletic Greens and the reason I still take Athletic Greens once or usually twice a day is that it gets me the probiotics that I need for gut health. Our gut is very important. It's populated by, uh, gut microbiota that communicate with the brain, the immune system, and basically all the biological systems of our body to strongly impact our immediate and long-term health.And those probiotics in Athletic Greens are optimal and vital for microbiotic health. In addition, Athletic Greens contains a number of adaptogens, vitamins, and minerals that make sure that all of my foundational nutritional needs are met, and it tastes great. If you'd like to try Athletic Greens, you can go to athleticgreens.com/huberman and they'll give you five free travel packs that make it really easy to mix up Athletic Greens while you're on the road, in the car, on the plane, et cetera, and they'll give you a year's supply of vitamin D3K2. Again, that's athleticgreens.com/huberman to get the five free travel packs and the year's supply of vitamin D3K2.

Andrew Huberman 37:37 Okay, so now at a minimum, everyone out there should understand that water has a particular structure. So when you hear H2O you can kind of imagine that structure, and that the water molecules can change their conformation, that is, they can bind to other water molecules and it turns out they can bind to other things and actually change the conformation of other things. A good example of that is something we're all familiar with, which is water's ability to dissolve certain substances like sugar or salt, and that is because salt molecules or sugar molecules are what we call hydrophilic. They like water. And when we say they like water, it just means that the chemical structure of salt, sodium, or the chemical structure of, say, sucrose, like table sugar, can actually interact with the hydrogens and oxygens of water and can change those salt molecules or sugar molecules, turning them from solid into liquid, essentially creating what are called solutes, which is basically the, the, um, dissolving of solids into a liquid solutions. In fact, water is one of the best solvents on the planet. In fact, water is better at dissolving many solids than is acid, all right? That's how incredible water is. And there are a number of reasons related to the chemistry of water that can explain that. But as we transition from talking about the physics and chemistry of water to how water actually behaves within our body and contributes to our health or to disease, depending on the case, it's important to understand that molecules, such as sugar and salt, can be hydrophilic or, as we know, oil and water don't mix. That's because oils, lipids are so-called hydrophobic. What's hydrophobic? We'll just think, "Ah, -phobic." Certain molecules, such as lipids, don't dissolve well in water, and we all intuitively understand that. If you take some olive oil, for instance, and you put it into a little glass of water, it'll likely float or bead up or form little spherical or amoeba-like shapes within the water, and that's because oil, lipids are hydrophobic. So different substances out there are either going to be more hydrophilic, that is they are going to, um, have a greater propensity to interact with water and bind with the different aspects of the water molecules, or hydrophobic, to have less of a propensity to interact with and bind with w- water molecules. And I've sort of been alluding to this numerous times throughout this podcast already, the temperature of water and the pH, that is the alkalinity or acidity of water, will have a strong impact on whether or not a hydrophilic or hydrophobic substance will have a greater or lesser tendency to interact with water. Uh, you all know this intuitively as well. If you've ever tried to dissolve, um, say, a big tablespoon of sugar in very cold water, you'll notice that the grains don't dissolve as quickly as when you take that big tablespoon of sugar and put it into a warm or hot cup of water, and that's because the temperature of water actually changes how well that sugar molecule is able to change its conformation and interact with the water molecules. Likewise, if you want to get something that's really hydrophilic into an aqueous, that is a water-containing solution, the temperature is also going to strongly impact that. Now, there are a near infinite number of examples of how temperature and pH impact the tendency of hydrophilic and hydrophobic substances to dissolve in water or not. We're not going to go into all those details, but as we migrate from our discussion about the physics and chemistry of water into how water behaves within our body, which is what we're going to do now, and then as we continue into the third part of our discussion, which is why and how certain types of water that some of you are familiar with, like different pH water, distilled water, reverse osmosis water, why those different types of water are thought to, and in some cases do in fact change the ways that our cells function, for better or for worse, all of that will come together and make sense for you.

Andrew Huberman 41:49 Okay, so all the cells of your body, every cell, even your bones, that is the osteoblasts and the other cells within your bones, your bone marrow, your red blood cells, your white blood cells, your neurons, your nerve cells, your liver cells, your kidney cells, all of them require water. In order to get the proper amount of water into those cells, there are basically two ways that water can access those cells. Now, if we zoom out for a second and ask ourselves, "How does water actually get into the body?" most of us just think, "Oh, well, we drink that water into our body." Of course, that's the main way. We can also breathe water molecules into our body through humid air. When you hydrate your cells, that is when you're bringing water into your cells, that water needs to move from your gut and into the bloodstream and eventually into the individual cells, whatever cell type that may be, and there are basically two ways that water can access those cells. The first way has been known about for a very long time, and that is so-called diffusion. Now, the outside of most cells is made up of fatty stuff, lipid. So for instance, neurons, nerve cells have a lipid bilayer. It's two layers of fat, and you already know that fat, lipid is very hydrophobic.Okay? Now, that turns out to be not a problem, but a solution for how water can get across that lipid barrier. Why? It is the fact that water can change its conformation and lipids can change their conformation just enough so that the bonds between water and the bonds between those hydrophobic lipids can interact, allowing the water molecule to basically pass through the lipid because it can bond very weakly, or in some cases not at all, but very weakly to those lipids and then be pushed through to the other side. Really incredible if you think about it. If there was too much of a hydrophobic relationship between the lipid and the water, the water would come up to the surface of that (laughs) of that fatty outside of, of our cells and then would be repelled away from it or it would just stay there right at the surface a- and that would be no good because we actually need that water to diffuse across the cell membranes, or actually it's a double cell membrane as I mentioned before, two layers. So water and lipids of cells can interact with just enough affinity that the water molecule can diffuse across those cell membrane barriers. But, and this is an important but, the diffusion of water molecules across those lipid barriers on the outsides of cells is a fairly slow process compared to the other way that water accesses cells. And this other way that water accesses cells is really something that was just discovered about 10 years ago, so this is a fairly recent discovery, which turns out to be a fundamental discovery, which is the presence of what are called aquaporin channels. Aquaporin channels are basically portals through the membrane that allow water molecules to move very quickly across cell membranes at a rate of about one million H2Os, one million water molecules per second. And the way that water molecules move across the cell membrane through those aquaporin channels is very interesting. The inside of those channels, and the way to think of these is they're literally tubes stuck up through the membranes of cells, the insides of those channels are very hydrophobic, allowing those water molecules to just jut really quickly, uh, almost as if in your mind you can just imagine as if it was sort of lubricated for the water, although it's not really lubricated. The, the water molecules can move through in single file, fshooshfshooshfshooshfshoosh, a million per second. Now, why would you need two ways for water to get across cell membranes? One fairly slow through basic diffusion, and again, diffusion, folks, is the movement of things from a gradient of higher concentration to lower concentration. We should just think about this as things tend to run downhill from higher concentration to lower concentration, they try and create equilibrium ac- across space. So, you know, if you had a bunch of marbles on one side of a, of a box, they're, um, just imagine that if these were water molecules th- because of the charges between those, um, hydrogens and oxygens, there's a tendency for those, um, marbles to spread out and essentially take on a fairly even conformation. That's basically just diffusion across a space. Water molecules will also move from higher concentration to lower concentration across cell membranes, and then you have these portals, these tubes or these channels as they're called, these aquaporin channels where water molecules can move very quickly. Now, the reason why biology seems to have created these aquaporin channels, and again, I wasn't consulted at the design phase, but the most logical explanation is that we have many tissues within our body that often need water very quickly or need to release water very quickly. Let's think about a couple of these and then let's look at what the actual distribution of aquaporin channels is throughout the body. What is an area of your body that on occasion will need to move water very quickly out of it? You can use your imagination here, but I'll just tell you that, for instance, your tear glands or tear ducts need to release tears very quickly, so you need to take water that's stored in your body if there's an emotional experience or if, uh, you look at a very bright light for instance, um, or, uh, you know, God forbid, if you get some, um, sort of irritant in your eye, you're going to start to tear up, and those tears are the release of fluid from those tear ducts. And so it's going to be the very rapid release of water, uh, from those tear ducts through so-called aquaporin channels. And in fact, aquaporin channels are heavily expressed. There are many of them in the cells of the so-called lacrimal glands that release tears. In addition, we need to absorb water from the gut, and the gut has a lining, endothelial lining, and other cell linings, mucosal lining, and water needs often to move very quickly from our stomach into the rest of the body, and one way that is accomplished is through aquaporin channels that are expressed all along your gut. So the discovery of these aquaporin channels is really highly significant in terms of understanding the different ways that water can interact with and get into the cells of your body. Now, there are aquaporin channels not just in the lacrimal glands that allow for tearing or within the gut, but in many tissues within your body and they're even have different distributions within those tissues. In fact, as one looks at the expression of the different aquaporin channels, 'cause it turns out there are different forms of them, across all the cells and tissues of the body, there's really no single tissue within the body except perhaps the bones of your body and perhaps the ligaments to some extent that don't have these aquaporin channels. Some of you out there may have heard of the so-called fascia. Fascia and sheath muscles are a unique kind of connective tissue that, um, gives some pliability and yet some rigidity that allow for a lot of the, um, physical abilities of your musculoskeletal system. It's incredible tissue. We'll do an entire episode about fascia at some point. Fascinating, fascinating tissue.Fascia even contain aquaporin channels, so the role of aquaporin channels and fascia probably relates to our specific needs to be able to use specific muscle groups in particular ways, at particular times. In other words, if you're sleeping or lying down or sitting, you're not using your musculoskeletal system as much as if you're running or r- performing some repetitive behavior. It turns out that the aquaporin channels in certain tissues like the fascia can be used when we transition from low mobility states to high mobility states, allowing more profusion or access of water into particular cells of the body when we need it, so just fascinating, fascinating, uh, channels, these aquaporin channels. And again, only discovered fairly recently, so we're still learning new things about our biology all the time. Now, and a very important feature of the aquaporin channel is that the movement of water molecules across the cell membrane through those

Andrew Huberman 49:46 aquaporin channels is strongly dependent on the temperature of water and the pH of water. This becomes especially important in our description and our deep dive into so-called alkaline water, or higher pH water, a little bit later. But I'll just give you a little teaser for now, because I'm sure that a number of people are, are wondering about this. If you go into the store, or even a convenience store, you will see pH water. Now, every water has a pH, right? Lower numbers mean more acidic, higher numbers mean more alkaline or more basic. You'll see pH water that is 7.4. You'll see 7.8. You'll see 9.8. (laughs) You'll see a huge range of these things, and there are many, many different claims about how the pH of water is important for regulating the pH of the body. Here's the real story. The pH of your body, that is the pH of the cells at different locations in your body, is strongly, strongly homeostatically regulated. What do I mean by that? It means it doesn't change that much, which means that you have very specific biological mechanisms that ensure the pH is maintained, for instance, in the skin cells of your skin, in the retinal cells of your eye, in your brain cells. Now, it is true that across the body different cells and tissues have fairly widely varying pH. You know, it has been said that the pH of bodily tissues is generally between 7.2 and 7.4, however, if you were to look at the pH of your gut, and keep in mind that your gut is not just your stomach, your gut is the entire pathway ranging from your throat all the way down, um, to where you excrete things out of your body. That entire pathway has different pH levels depending on where you are along the gut and intestinal pathway, and in fact, having much lower, that is more acidic pH at certain locations along your gut pathway is what allows those gut microbiota, those, um, little microorganisms of which you have trillions and that are important for regulating everything from neurotransmitter production to hormone production, that allow them to flourish and do well. That said, except under conditions of hemorrhage or, um, changes in blood volume that are of a dangerous level that can lead to seizure or even death, the pH of the rest of the cells of your body, and also those gut cells, doesn't change that much on a moment-to-moment basis. So if somebody tells you that you should drink alkaline water, or alkalinized water as it's sometimes called, in order to keep your body more alkaline and less acidic, there is essentially no basis for that at a macroscopic level, or even at a local level. Now, what that does not mean is that the pH of the water that you drink is not important. In fact, if the pH of the water that you drink is too low, that is if the water that you consume is too acidic, it will not move as quickly from your gut into the other regions of your body, and therefore the other cells of your body that require that water will not be able to access it as readily. You've probably experienced this if you've consumed certain water and it feels like it's sloshing around in your stomach, or it feels like it's, um, just somehow staying there, or you feel it, its presence more, not just as volume, but it's almost as if you can feel the little waves of water along the inside of your gut. Now, sometimes that can relate to temperature, but oftentimes that can relate to the pH of that water. And it turns out it is true that water that is more alkaline, that is pHs of 7.4 or higher, can move more readily across the aquaporin channel. And in terms of absorption of water from the endothelial lining and the other cell type lining of your gut into the rest of your body, it is true that higher pH water, provided that pH isn't too high, is going to be absorbed more quickly, which partially explains why some people have an affinity for this higher pH water. Now, this is not to say that you need to consume high pH water in order to hydrate your body properly. I wanna be very clear about that. However, if you are interested in what the value of elevated pH water is, it largely has to do with this accelerated absorption. And as we'll talk about a little bit later, there is also growing evidence that it can adjust the function of certain cells that are within your immune system, and thereby reduce certain inflammatory responses. So I realize (laughs) as I'm saying this, some people out there are probably thinking, "Oh, no. This guy's like a pH water proponent. He's saying we have to drink alkaline water or buy very fancy water." Now, I want to be clear. That is not what I'm saying, and I'm also not saying that you need to purchase very expensive water in order to derive the maximum benefits from the water that you drink. It turns out there are a few things that you can do by way of temperature and by way of filtering water, and a few other tricks that I'll tell you a little bit later, that will allow you to increase the absorption rate of water in the gut, which turns out to be a very...... interesting, but also potentially important thing to do for not just reducing inflammation, but also making sure that you're getting proper hydration of different cell types in your body, including rapid hydration of your brain cells, which, as we'll also talk about in a few moments, can greatly enhance cognitive function. Okay,

Andrew Huberman 55:14 so we've talked about how water can get into cells, there are two ways; diffusion and movement through these aquaporin channels. We've earmarked the discussion that the temperature and the pH of water, that is the conformation of water, and here I really want to embed this in people's minds, that when we talk about temperature of water, and pH of water, we're really talking about the arrangement of those H2Os, those water molecules, so keep that in mind. We've covered how water can get into cells through those two different ways, diffusion and through aquaporin channels. What we haven't talked about is what happens to water once it's in cells. And this is very simple to explain. Once water is inside of cells, it's going to be incorporated into the different proteins and organelles, again, organelles are things like mitochondria, the nucleus of the cells, which is, contains the DNA and so forth, in different ways, depending on which proteins are there and how hydrophilic or hydrophobic those proteins are, or in some case aren't. That's an entire landscape of protein to water specific interactions, none of which we need to go into in any specific detail now, but the one thing that we do need to realize and keep in mind as we go forward is that many of the biological processes in our body that involve the movement of molecules such as water and interactions with proteins are going to involve the bonding or lack of bonding between water molecules and proteins. And any time we're talking about bonding of one thing to the next at the level of chemistry or biology for that matter, 'cause they're really the same thing, we're talking about whether or not there are electrons present or whether or not there are charges that are opposite or the same and on and on. If you've ever heard of so-called reactive oxygen species. What are ROSs or reactive oxygen species? Or so-called free radicals or antioxidants? All of that is really just describing the presence or absence of charges that are bound or unbound. So for instance, if you hear about free radicals, sounds pretty wild, right? Free radicals. What are free radicals? Free radicals can damage cells, they don't always damage cells, but they can damage cells because they are essentially free electrons. They are a charge that's sitting out there, not bound to anything, and therefore can interact with the molecular structure of certain proteins and change those structures by binding to them or interfering with the normal binding processes of those proteins to water or to other things, and in that way cause damage to those proteins and potentially damage to cells. Now fortunately, our cells have ways to deal with those free radicals, and those are called antioxidants. Antioxidants are molecules that can arrive in different forms, sometimes we think of antioxidants as vitamins, but they are also present in other things as well, that essentially bind up those free radicals or repair the bonds between cells so that the proteins are no longer undergoing these, let's just call them bad conformations that damage the functioning of our cells. So there are many different theories of aging, there are many different theories of disease, but there is not a single disease either of brain or body that doesn't in some way involve the generation of what are called reactive oxygen species, these free radicals and the damaging of cells at the level of their individual organelles and so forth, nor is there a single disease of brain or body that has not been shown to benefit from having some antioxidant interference get in the way of that oxidative process. So I realize today is pretty thick with nomenclature. Um, for those of you that haven't already realized it, what you're learning here is organic chemistry. So, um, you can feel pretty good about the fact that if you can understand the water molecule and, uh, understand a little bit about what, um, uh, free electron is, which is basically a charge that's out there that, um, can potentially do damage and the interactions of things like reactive oxygen species and the ability of, of stable bonds to, um, buffer against or, or repair certain damage to cells as we're describing it here, well then what you're essentially thinking about and what we're talking about is organic chemistry. Now, since this is a discussion about chemistry as a service to try and understand the biological effects of water, keep in mind that water itself, believe it or not, can act as an antioxidant provided that it's bonding to things in the proper way, which requires that it get into cells in the proper amounts and rates, which requires that the temperature and pH of that water be correct, and provided that there's enough water there and that that water isn't bound to other things, it's not containing solutes that are damaging and potentially that it's carrying some of the good things such as sodium or that there's potassium present. Again, the so-called electrolytes that allow cells to function well. Okay? So, um, that's a bit of a trench of information and I don't want people to get overwhelmed or confused. What I'm trying to do here is paint a picture of the biology of water, understanding that when you ingest water, drinking it down, or when you breathe water vapors in the steam room or on a humid day, that water is entering your system, it's accessing your cells through these two mechanisms; diffusion across cell membranes or movement through aquaporin channels, and then once inside those cells, it's able to interact with and change the conformation of different proteins and accelerate or slow down different cellular r- reactions. Everything from normal metabolism, to blood pressure, to damaged cells, depending on a number of different features of that water as well as what the cells happen to be doing at any given moment.So with that in mind, I'd like to turn our attention to how water, depending on its temperature, its pH, how much we drink or how little we drink, when we drink that water, et cetera, how that can impact the health, disease, and repair of different cells, tissues, and organs of

Andrew Huberman 1:01:20 our body. I'd like to just take a brief moment and thank one of our podcast sponsors, which is InsideTracker. InsideTracker 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've long been a believer in getting regular blood work done for the simple reason that blood work is the only way that you can monitor the markers such as hormone markers, lipids, metabolic factors, et cetera, that impact your immediate and long-term health. One major challenge with blood work, however, is that most of the time it does not come back with any information about what to do in order to move the values for hormones, metabolic factors, lipids, et cetera, into the ranges that you want. With InsideTracker, changing those values becomes very straightforward because it has a personalized dashboard that you can use to address the nutrition-based, behavior-based, supplement-based approaches that you can use in order to move those values into the ranges that are optimal for you, your vitality, and your longevity. InsideTracker now includes a measurement of apolipoprotein B, so-called apoB, in their ultimate plan. ApoB is a key marker of cardiovascular health, and therefore there's extreme value to knowing your apoB levels. If you'd like to try InsideTracker, you can go to insidetracker.com/huberman to get 20% off any of InsideTracker's plans. Again, that's insidetracker.com/huberman to get 20%

Andrew Huberman 1:02:38 off. Let's talk about how much water, or more generally speaking, how much fluid each and all of us should drink each day and how much fluid to drink depending on our specific activities and environment. Now, this is perhaps the most commonly asked question when the topic of water comes up. How much water do I need to drink? The other thing that comes up is a question, which is, can't we just follow our natural thirst? That is, can't we just pay attention to when we're thirsty and then drink fluids? And then that leads to the other question, which is, does the color of our urine provide any indication as to whether or not we are under-hydrated, over-hydrated, or hydrating correctly? So let me answer each of these things one at a time, and in the backdrop, I want to highlight the fact that there are many, many, if not dozens, hundreds of studies pointing to the fact that when we are dehydrated, our brain doesn't function as well and our body doesn't function as well. So what I'm attempting to do in that statement is throw a net around the enormous number of studies that have shown that even a slight state of dehydration, even 2% dehydration, can lead to a significant and meaningful impact, that is a negative impact, on our ability to, for instance, carry out endurance-type behaviors. So our ability to, uh, run on a treadmill and stop at the point where we feel like we can't continue is going to be negatively impacted. That is, we will be able to perform less work for less period of time when we are even slightly dehydrated. Likewise, our strength is reduced by even slight dehydration. Likewise, our cognitive performance, including memory, focus, creative thinking, flexible thinking of different kinds, are all significantly impaired when we are in states of dehydration. Now, that raises an additional question that deserves attention, which is, how do we actually measure dehydration? You know, you hear different things, like if you pinch the skin on the top of your hand and it takes more than three seconds to, uh, lay down again flat, then you're dehydrated. You hear that. You hear, okay, if you are to, uh, press on your fingernail and see a change in the color of the tissue just belo- below your fingernail, which indeed does happen, and it does not go back to its original color within one to three seconds, then you're dehydrated. You hear things like this. If your ankles are swollen when you're wearing (laughs) socks, you take off the socks and you can see the imprint of the socks on your, uh, lower limbs, that means you're dehydrated. You hear this kind of stuff, and you should probably be wondering, is any of that true? To some extent, it is true, although it can vary (laughs) quite a bit by how old you are, whether or not your, um, skin on the top of your hand tends to be looser or not, depending on whether or not you're leanier or not. So in other words, those are not absolutely objective measures of dehydration. Now, it is true that if normally you can pinch the skin on the top of your hand and it returns to its normal flattened position within about one to two or three seconds, and it does not do that within five or more seconds, there's a decent probability that you're a little bit dehydrated, that you need to ingest some fluid. Or that if you press down on your nail and you see the depression, uh, causes a, uh, transition from kind of a pink color to a white color and then you release and it doesn't go back to its original pinkish color within a few seconds, well, then there's a chance that you're dehydrated. But again, these are not perfect measures of dehydration. You may be surprised to learn, and I was surprised to learn, that most of the basis for these statements, like even a 2% dehydration state can lead to significant reductions in cognitive or physical performance, are based on not direct measures of hydration, but rather on measures of reductions in water intake, which is a different thing, right? It's saying that ordinarily a person of a given body weight needs X amount of fluid per day, and when they get even just 2% less than that amount of fluid, then their cognitive and/or physical performance is impaired, rather than focusing on dehydration of tissues. Okay? Now, that might seem like a, um, subtle distinction, but it's actually a meaningful distinction when you think about it. However, it's a meaningful distinction that we can leverage toward understanding how much water or fluid we need to drink each day. Now, there we can really point to some solid numbers that, believe it or not, are fairly independent of body weight. Now, I say independent of body weight. I'm referring to the amount of fluid that most healthy adults need...... at rest. What do I mean by at rest? I mean when not exercising and when not in extremely hot environments. So I'm leaving aside you, uh, desert ultra-marathoners or people that are doing any kind of movement or living in environments that are very, very hot. Here, I'm mainly referring to people that live most of their daily life in indoor environments, could be air conditioned or not air conditioned, heated or not heated. What we're trying to arrive at here are some numbers that can work across the board, because of course, there are an infinite number of different conditions that each and all of you are existing in. So I am not going to attempt to give you a body weight, by activity, by environment, by humidity (laughs) formula calculation. In fact, no such calculation exists. However, there are formulas that can put you into very stable frameworks, that is levels of water intake for periods of rest when you're not exercising and for when you are exercising that will ensure that you are hydrating, with the one exception being if you are exercising or if you are living in very, very hot conditions and you're not heat adapted to those conditions. So what are those numbers? In other words, what is the answer to the question of how much fluid do we need each day? And here, I'm referring to fluid. I'm not distinguishing between water, caffeinated beverages, soda, tea and so on. I'll discuss that in a moment. We can reasonably say that for every hour that you are awake, in the first 10 hours of your day, this is important, in the first 10 hours of your day, you should consume, on average, eight ounces of fluid. Now, for those of you that are using the metric system, not ounces, eight ounces of fluid is approximately 236 milliliters of water. And for those of you that exist in the metric system and aren't used to thinking about ounces and vice versa, just think about a typical can of soda in the United States, it's 12 ounces. In Europe, sometimes the cans of soda are a little bit smaller, uh, that's a whole 'nother discussion unto itself, but eight ounces of fluid, that is 236, so let's just say 240 milliliters, 'cause we don't need to be too precise here, of fluid, on average, every hour for the first 10 hours of your day, which translates to an average of 80 ounces of fluid for the first 10 hours of your day, or 2,360 milliliters of water. In other words, approximately two liters of water plus a little bit more for the first 10 hours of your day. Now, I want to be very clear that this does not mean that you need to ingest eight ounces or 236 milliliters of fluid on the hour every hour for the first 10 hours of your day. I'm certainly not saying that. And in fact, most people are going to find that they're going to ingest water in boluses, that is they're gonna have, uh, perhaps 16 ounces of water, 500 milliliters of water at one portion of the day, and then maybe a couple hours of later the- they'll drink some more water or some more coffee or soda or some other beverage in another portion of the day. I do think, however, it's important for most of us to take a step back and ask ourselves whether or not independent of any other activity or environmental conditions, whether or not we are in fact ingesting 80 ounces or basically 2.4 liters of water for that 10 hours of the day that spans from the time we wake up until 10 hours later. Now, why am I setting this 10-hour framework? The reason I'm setting this 10-hour framework is that it turns out that your fluid requirements, even just at rest, are vastly different in the time from when you wake up until about 10 hours later as compared to the later evening and nighttime. And here, I'm referring to people that are not doing night shifts, but if you are requesting a number of how much fluid to drink, independent of our needs for fluid for exercise, that's going to be eight ounces of fluid or 240 milliliters of fluid on average for every hour from the time when we wake up until 10 hours later. That's the simple formulation that should basically ensure that you're getting sufficient baseline hydration for the cells and tissues of your body. Now, if you

Andrew Huberman 1:11:35 are engaging in exercise, whether or not it's endurance exercise or whether or not it's resistance training exercise, you are going to need additional fluids in order to maximize the effects of that exercise and to avoid dehydration, and there too we have some excellent numbers that we can look to, excellent because they arrive from research, and this is largely peeled from the episode that I did with Dr. Andy Galpin, Professor of Kinesiology at Cal State Fullerton. We did a six-episode series all about exercise, everything from strength training, hypertrophy, endurance, nutrition, supplementation, recovery, everything related to exercise. You can find all of that at hubermanlab.com, and one of the components of those episodes that was discussed but that some of you may have not heard is that there is a simple formula for how much fluid to ingest on average, keep in mind this is on average, when you are exercising, and I refer to this as the so-called Galpin Equation. The Galpin Equation states that y- you should take your body weight in pounds, divide that by 30, and that will give you the number of ounces of fluid to ingest every 15 to 20 minutes on average while exercising. Okay? Your body weight in pounds divided by 30 equals the number of ounces of fluid to consume on average every 15 to 20 minutes. When I say on average, what I mean is, it is not the case that you need to stop every 15 or 20 minutes and consume that volume of fluid. You could sip it from moment to moment. You could wait half an hour or an hour and then consume a larger bolus of fluid, a larger amount, although it is recommended for f- performance's sake that you sip or consume beverages fairly...... consistently throughout your training. One's ability to do that is going to depend on a number of things like gastric emptying time, whether or not the particular exercise you're doing, whether or not it's running or jumping, is compatible with ingesting fluid on a regular basis, or whether or not you need to do it at different intervals than every 15, 20 minutes, maybe it's every five minutes, maybe it's every half-hour. You have to adjust for you. But if you were to take the hour of exercise or the half-hour of exercise, or the three hours of exercise and ask how much fluid to ingest, it's going to be that Galpin equation of body weight in pounds divided by 30 equals the number of ounces for every 15 or 20 minutes. And of course, I can already hear screaming from the back, "What about for those of us who follow the metric system?" And there, there's a simple translation of the Galpin equation, which is that you need approximately two milliliters of water per kilogram of body weight every 15 to 20 minutes. Again, the Galpin equation converted into the metric system is going to be two milliliters of water per kilogram of body weight every 15 to 20 minutes on average. I'm sure a number of you are asking whether or not hydration prior to exercise is also important. It absolutely is. And if you follow the numbers that I talked about before, approximately eight ounces or 240 milliliters of fluid intake per hour in the first 10 hours of waking, that should establish a good baseline of hydration heading into exercise. Which then prompts the next question I often get, which is, is the amount of water that needs to be consumed according to the Galpin equation during exercise on top of or separate from that- that is, does it replace the amount of fluid that one needs at a basic level, that eight ounces or 240 milliliters? And there, the answer sort of goes both ways. I think if you're going to exercise, then obviously follow the Galpin equation in some way. Again, you don't need to be ultra-specific about this. These are ballpark figures that will ensure hydration, so we've set them a little bit higher perhaps than needed to ensure more hydration rath- rather than less. But basically, the short answer is, if you're exercising for about an hour, most people are exercising for an hour or two, probably not more than that. Most of my, uh, workouts are, certainly the resistance training workouts last about an hour. Well, then you can replace the eight ounces or the 240 milliliters of water that's required at baseline with what you consume according to the Galpin equation during that bout of

Andrew Huberman 1:15:40 exercise. A common question is, if you are exercising in a heated environment, indoor or outdoor, or you are somebody who tends to sweat a lot, and by the way, we can all get better at sweating by sweating more. Sweat is an adaptation. So if you sit in the sauna more, you're going to get better at sweating. If you exercise more, especially if you wear more layers or if you do it in hotter temperatures or more humid temperatures, you're gonna get better at sweating over time, and sweating is an adaptation that helps cool your body. If you are sweating a lot or you're in heat, how much fluid should you ingest? In general, I think it's safe to say that you may want to increase the values on the Galpin equation by about 50 to 100%. So either increase by 50% or double those numbers if you're in a very hot environment or sweating an awful lot. If you are sitting in the sauna, I highly recommend consuming at least eight ounces and probably more like 16 ounces of fluid, so that translates again to about 240 or about 480, let's just round up, 500 milliliters of fluid for every 20 to 30 minutes that you are in a hot sauna. And then of course people ask, "Well, how hot?" And it, okay, that starts getting really detailed and we can't distinguish between dry saunas and wet saunas, and again, too many variables. But I would double your fluid intake for that hot environment exercise or for that hot environment sauna sit. Um, also, if you are feeling dehydrated, okay, what does feeling dehydrated mean? (laughs) That actually has a, a definition that we can get into a little bit later. But what we're really talking about here is if you are feeling as if your throat is dry, you are, quote-unquote, "parched," or you're very thirsty, well then there's absolutely no problem with ingesting more fluids, so 16 ounces of fluid or 500 milliliters of fluid per hour while you're feeling parched. My read of the literature is that thirst is a reasonable guide for when we tend to be dehydrated. However, it is the case that our thirst doesn't really keep up with our body's level of dehydration, and we know that based on some really nice studies that have explored the amount of fluid intake compared to the amount of urination compared to the amount of physical output compared to the environment that one happens to be in. And these are, um, sort of older studies in the realm of physiology. But here's the basic rule of thumb that's gonna work for most people. If you are feeling parched, consume fluids. Ideally, you consume fluids that don't contain caffeine or other diuretics, diuretics being, um, substances that cause the release, the urination of fluid from the body, and/or if you are consuming caffeine either prior to or after bouts of exercise or even just at work or you work in a air conditioned or otherwise dry, cool, or hot environment, that you try and include some sodium, and ideally sodium, potassium, magnesium, the electrolytes in that beverage. So it could be a little pinch of sea salt with some lemon to adjust the taste a little bit, it could be an electrolyte drink, LMNT or some other sort. There are a lot of different types out there. For most people drinking pure water, and I realize that many people do just like the taste of pure water, chances are you're going to have enough electrolytes unless you're sweating quite a bit or you're exercising quite a lot, and under conditions where you are consuming very few carbohydrates, you're going to excrete more fluid. If you are ingesting caffeine, whether or not it's from tea or coffee, I highly recommend increasing your non-caffeine fluid intake about two to one for every volume of caffeine. So, in other words, if you have six ounces or eight ounces of coffee, you're going to want 12 to 16 ounces of fluid, ideally fluid with electrolytes or a little pinch of salt, in order to offset that dehydration.So

Andrew Huberman 1:19:16 hopefully those will provide good rules of thumb for what people want to do when they're just moving about their day. Again, underscored by the fact that even slight levels of dehydration can really impair our cognitive and physical performance, largely by creating fatigue, but more often than not, by creating brain fog. You know, I get so many questions about brain fog. "Why do I have brain fog? Why do I have brain fog?" There is a vast literature showing that quality hydration, meaning hydration that matches the demands of humidity and output as described in the equations be- that we went over a little bit before, really can enhance clarity of focus and overall energy. And we'll talk about why that is, but I'll just allude to it, uh, a little bit here. The reason why ingesting sufficient fluids can enhance our ability to focus and in fact can reduce brain fog and can increase physical vigor and output is not mysterious to us. We know that there are two mechanisms by which fluid intake triggers elevated levels of alertness, and it all has to do with the so-called sympathetic arm of the autonomic nervous system, which is a real mouthful. But basically the sympathetic arm of the autonomic nervous system, as many of you have heard me talk about before, is the aspect of your nervous system that makes you more alert. It has nothing to do with emotional sympathy. It has to do with a bunch of neurons in the middle of your spinal cord called the sympathetic chain ganglia and some other related neural networks in your body, as well as regions of your brain like the locus coeruleus that release things like epinephrine and norepinephrine and make you more alert. And in a kind of magnificent arrangement, or I think magnificent arrangement, when we have fluid in our gut and when our cells are well hydrated, and believe it or not, when our bladder contains fluid within it, there is an elevation in activity of the sympathetic nervous system by way of two pathways. One is mechanical. In fact, we have so-called