#200 - AMA #33: Hydration—electrolytes, supplements, sports drinks, performance effects, and more

Hey everyone. Welcome to a Sneak Peek, Ask Me Anything or AMA episode of the Drive podcast. I'm your host, Peter Attia. At the end of this short episode, I'll explain how you can access the AMA episodes in full, along with a ton of other membership benefits we've created. Or you can learn more now by going to peterattiamd.com subscribe so without further delay, here's today's sneak peek of the Ask Me Anything episode. Welcome to Ask me anything episode 33. I'm joined once again by Nick Stenson. In today's episode we talk about all things related to hydration. So got a lot of questions about hydration and personally this has become something that's a lot more interesting to me in the past couple of months than it had been previously for reasons I'll explain in the podcast. So we kind of do, I think a tour de force on this here. We had actually intended to talk about a few other unrelated topics, but we went so long on hydration that we just decided to make this a dedicated episode to that. So we kind of get into where does water live in our body? You got to start from the standpoint of understanding where are the water compartments of our body. And then you have to get into this idea of tonicity. So it gets a little sciency up there. But then once you understand that, and I think it's pretty straightforward to understand everything, everything that we start to talk about makes sense thereafter. So we get into kind of the difference between dehydration and volume depletion, what the health consequences of that are, how we're actually losing water, how much water we need throughout the day, how much water versus salt you're losing when you sweat, and how that changes under different conditions and therefore what your hydration needs look like under different conditions of temperature and exertion. Talk about how dehydration affects performance, what the signs look like of dehydration, and we even get into what happens when you over hydrate. So that's something that is fortunately rare but unfortunately can be quite catastrophic. And then we kind of get into all of the different ways one can rehydrate. So what's the difference about rehydrating with electrolytes only versus electrolytes plus glucose versus glucose only. We then get into all of the different sports drinks and how they're put together, which ones are based on scientific principles, maybe which one's less so even getting into kind of the nuance around the optimal ratio of glucose to sodium. So if you're a subscriber and you want to watch the full video of the podcast, you'll be able to see it within the show notes. If you're not a subscriber, you can watch a sneak peek of the video on our YouTube page. So without further delay, I hope you enjoy AMA number 33. One addendum to this podcast since it was recorded this AMA was recorded in early January of 2022. At that time, I had no involvement with any company producing any of the hydration products that are discussed here. However, since recording this podcast, I've continued down the rabbit hole of getting deeper and deeper into this. I've become particularly enamored with one of the companies that I mention here, and I am now a small investor in that company. That company is Element lmnt. So understand that while I now have a financial conflict of interest through my investment in Element, I did not have that at the time of this podcast. All right, Nick, we're. We're back for another ama. This is your second one. So you survived the first one, huh?

Yeah, I made it through the first one. So we'll see how this one goes.

All right. I don't know. I think we've got some interesting topics for today. What do we have?

We have a good amount of questions that came through around hydration. All things that relate to that, which I know is a topic you became a little more interested in in the recent weeks and months. I'm sure people, even if they haven't heard the stories, might have seen the scars on your face and some podcasts and things like that, which are healing nicely. So why don't you kind of give people a quick rundown of where this interest came from? Not that you weren't interested before, but where this additional focus.

Yeah, yeah, it's definitely a renewed interest. Actually, the story you're referring to was from the time of this recording several months ago, it was kind of a perfect storm of things. So I, on a Tuesday, gave a lot of blood, about three units of blood, and on the Thursday, so two days later, hopped on a long flight from here down to Brazil for the F1 race. And of course, anybody who's been on an airplane knows how dry they are and how dehydrated anybody gets on an airplane. On top of that, it was like an overnight flight. So you're basically asleep most of the time anyway, get to Brazil. It's Friday morning. I think I woke up in the morning when I was there. So it's between the giving the blood, the being relatively Dehydrated, and then just. I naturally have very low blood pressure anyway, and at least once or twice a month when I stand up from bed, I have to take a knee to just not fall. It's not like I never lose consciousness or anything, but anyway, you can see where this is going. Got up in the morning and this time completely lost consciousness. Have no recollection of how it happened, but just face planted into a table. And the only thing I remember was the sound of my neck cracking and then waking up looking like there was a murder scene in the room. It's funny, at the time, I didn't put two and two together. I didn't understand why I could have such a horrible fall and truly lose consciousness. And then, of course, after the fact, putting two and two together and realizing actually you were profoundly dehydrated. So that kind of got me thinking, well, how can I mitigate this sort of thing from happening again? And what does it say overall about my hydration status? Is that partly what may contribute to why I sometimes feel lightheaded in the mornings? Yeah.

It's kind of funny when you think about it. Your biggest injury from racing in F1 came from travel to a race as opposed to in the race car itself.

That's right. That is, hands down, my biggest injury that involves any racing that I've done.

Or observed, including in a minivan.

Yes, definitely. The biggest challenge is just the family screaming at you when you race.

Well, you just got to enjoy the ride. They just got to sit back and enjoy where they're headed. Getting into this hydration thing, I think one thing that would be interesting is oftentimes people, and I've heard this before, your body's 50% water. Your body's 70% water. Your body's 60% water. You kind of hear over and over, like, your body. Body is so much water. And so when you talk about gaining weight, losing weight, you often hear the term water weight. So just stepping back, what does it even mean that our body makes up anywhere from 50 to 70% of water. Do we know what percentage it is? Where is it located? Maybe you lay the groundwork there.

This is a bit confusing. First of all, it does change a little bit. So infants have a higher percentage of their total body in water than adults. So I think using 60% is a reasonable number because that's about where adults are. So what does that mean? You want to divide that into two categories, broadly. The first is water that is inside of cells, and the second compartment is water that is outside. Of cells. So obviously we're made up of trillions of cells. So the water inside of cells is called, not surprisingly, intracellular fluid. And that accounts for two thirds of your water weight. So if you we're talking about 60% of your weight is water, then 2/3 of that 60% is within the cells themselves, which of course implies that one third of that weight is extracellular fluid or fluid that is outside of cells. Now this is where it gets a little more confusing, because that extracellular fluid resides in different places. Now, one of those places is pretty obvious, which is the vasculature. So you take blood out of the vascular system. Obviously water is a non trivial component of that. And it turns out it's about 25% of the extracellular fluid is the plasma that makes up the blood. Right. So blood is made up of cellular contents, clotting factors, things like that, and then of course, plasma. And you'll notice this anytime you spin blood or see blood spun, the tube, it's red, you spin it and all of a sudden it gets very dark at the bottom. That's like all the cellular contents. Predominantly what you're seeing is of course the platelets and the red blood cells, which dominate everything else. And then you see a clearish yellow fraction, depending on how much lipids are in there. That's the plasma, which is effectively the water. So 25% of the extracellular fluid resides in that space. About 2/3 to 60% of the extracellular fluid resides in what's called the interstitial space. So this is the space that is between cells, but not in plasma. This is very complicated. This is a space that is underappreciated. So when you have a cold or you're really, really sick, some people notice they actually might gain weight. And then they might notice that if they're really paying attention, in the days after they're starting to get better, not only are they losing weight again, but they're peeing like crazy. That's because of the expansion of that interstitial space. So when we're sick, our blood vessels become very leaky. And the reason for that is important. That's where we have all the white blood cells and immune cells do something called extravasate from the vascular system so that they can go and reach the tissues. But that leaking is what leads to this swelling. A more extreme example of this is somebody in the ICU who's very sick. They almost always look like a puffed up Michelin man, and that's the reason why. So the Remaining part of the extracellular fluid basically resides in the digestive tract, the CSF or other small fluid filled areas within epithelial line spaces. So the way you can sort of put a bow on this is about 67% of your total body water is inside cells. About 20% is in the interstitium, this area that exists between everything. And of course that can really expand when you're sick. About 8% is in the vascular system, and about 5% or thereabouts is basically everything else, including CSF and things like that.

Do those percentages, the overall percent of water in someone's weight as well as the breakdown of percent, does that change based on body types? Like if someone's leaning, if someone has more muscle, if someone has more fat, and maybe even a follow up is like, does that even matter if you're 60% compared to 65? It's probably what your baseline is as opposed to where you are compared to someone else.

But it does change for sure. So muscle is far higher water content than fat. So fat tissue is about 10% water by weight. We refer to that as being quote, unquote anhydrous. Without water, muscle is probably 75% water. So right there you can see you take two individuals. One of them is 12% body fat, the other is 35% body fat. There's absolutely going to be a difference in how much water that person is carrying. The more muscular person has a higher amount of their body weight made up in water.

So I mean, Bob Kaplan, he's probably what, 80, 90% water weight then with all the muscles he's rocking.

I think Bob is pure water. Pure water, just pure water.

Who was it, Bruce Lee? Like, this is water just takes it to a new extreme.

That's right. Well, this is water, of course, was David Foster Wallace, but I think Bruce Lee was.

Oh, move like water.

Yeah, taking the form of water.

Yeah, yeah, I got my water mixed up. Another term you hear a lot is tonicity. When talking about hydration, water levels, things of that nature, I thought it may be good to just get an idea of what that is. How does that play into everything here?

Tonicity basically refers to how the concentration of one solution compares to that of another. And the way we think about this in human physiology is all relative to the concentration of a cell because the cell is the dominant source of water. So if you ask the question, I think red blood cells are the easiest way to see this. If you put a bunch of red blood cells into another fluid, how would the water move between Those two. So let's start with the easiest example of this. The easiest example is something that is isotonic. We have a figure that shows this. Right, Nick, you want to whip that up?

I just pulled that figure up so people can see what we're talking about here.

Okay, so what you're looking at are a bunch of red blood cells in a solution where the surrounding solution has a different concentration of solutes in it relative to the red blood cell. So in a moment, I'll tell you what the concentration is of the red blood cell, meaning I'll tell you what the concentration, how much solute, I.e. electrolyte, is dissolved within that. For the purpose of this discussion, you just want to understand that there's an equilibrium. So if you put those red blood cells into a solution that has the same tonicity as them, there's a total balance between how much fluid goes from the outside solution to the cells and how much goes from the cells to the outside solution. So the red blood cells don't really change in shape at all. Now, what happens if you put the red blood cells into a very concentrated solution? So we would call that hypertonic. So if you did that, you would have a net flow of water from the red blood cells into that solution. Why? Because just like water always rolls downhill, water always moves in the direction of the concentration gradient. There's a natural equilibrium that's always trying to happen where water is trying to equate the concentration across the permeable membrane of the cell. So in a hypertonic solution, the cells would shrivel up as they lose water into the more concentrated surrounding solution. And of course, the opposite is true. If you put water into a hypotonic solution, there's going to be an influx of water into the cells, and they'll eventually swell, swell, swell, until they actually would rupture. Does that make sense, the difference between hypertonic, hypotonic, and isotonic? This is important. If we don't get this right, I think a lot of what we talk about today will be harder to follow.

Yeah, I think that does make sense.

And just as an aside, anyone who's been in a hospital has seen someone getting intravenous fluids. You've probably noticed you never give somebody water intravenously. Even sterile water. You couldn't give that intravenously because it doesn't have any tonicity. So the tonicity of pure water is essentially zero. So if you just infused water into somebody's vascular system, you would rupture all the cells in their body that would be a really bad thing to do. So when we give IV fluids, we have to give them relatively close to isotonic solutions. They don't have to be always isotonic, they can be a little hypertonic. And that's something that you typically do with people that have head injuries. As you're trying to reduce the swelling in their brains, you're actually trying to suck fluid out. And then you can also give slightly hypotonic solutions, especially if a person already has too many electrolytes on board, their sodium levels are getting too high and things like that. But as a general rule you're starting from the baseline of giving an isotonic solution which is 0.9% sodium chloride, and then you can adjust up or down with how much sodium chloride is in there and also how much other minerals ions are in there along with things like glucose which contribute to tonicity as well.

Got it? Kind of on that realm then one of the follow up questions we got was what are some of the most important solutes for determining the tonicity of bl? Are there certain things that are more important than others? How do you look at that?

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Sam.