Are Electrolyte Supplements a Scam? Dr. Alan McCubbin Explains

You've been told to take salt tablets. You've been told to stay on top of your sodium. You've been told to match a certain sodium to water ratio or to buy the electrolyte mix with the fancy numbers on the label. But what if most of it is wrong? Are electrolytes actually a scam? Have we been drinking way too much sodium, or have we been thinking about sodium the wrong way the entire time? These questions are popping up everywhere in endurance sport at the moment because the marketing has been outrunning the science, and very few people have. have the evidence and science to give answers to these questions, except for today's guest. Dr. Alan McCubbin did his PhD on sodium in endurance athletes specifically and has spent the last decade and more researching exactly this. That makes him one of the most qualified people on the planet to give you the answers you're looking for. He's a senior lecturer at Monash University. He's a sports dietitian, and he's consulted some of the highest performing endurance athletes in the world on sodium and electrolytes and sports nutrition. We can't wait for you to hear this episode. Enjoy. Dr. Alan McCoven, thank you very much for joining us on the podcast. We can't wait to dive into everything salt and sodium with you.

Not a problem, Jordy. Pleasure to be here.

I want to dive straight into it and ask a pretty broad question, which we might end up taking the whole episode to answer, but are electrolyte supplements a scam and are we completely misguided with sodium recommendations at the moment?

Well, I could say yes, but maybe I'll come up with a bit of a better answer than that. Look, I think there is a place for them and obviously we'll get into, you know, the role of sodium and where it may or may not be useful, you know, before, during, and after exercise. I think the trend that we're seeing at the moment is that everyone should have electrolytes every day, first thing in the morning, no matter whether you're exercising or going into an air-conditioned office and spending the whole day sitting at a computer. That, I think, is the bit that's, uh, very dubious.

Yeah. Yeah, it's a great starting point and we, we really want to, um, throughout the conversation try and separate, you know, what the general population is hearing versus what our audience and, and you guys listening as athletes are hearing. And, and yeah, I guess that leads to the first question that, you know, people will say, okay, maybe the general population doesn't need it, but athletes are exercising for very prolonged periods every single day on repeat. Um, therefore they need higher fluid intake and therefore we all assume higher sodium re-intake. But your research and, and papers, uh, point to pretty clearly that that's, that's kind of not the case and, and, and it doesn't really matter from an external to training point of view.

Yeah. So I think from a, like a day-to-day point of view, Putting aside the, you know, specific scenarios of like immediately before exercise or during exercise or post-exercise, but just in terms of, you know, day to day, that assumption that, oh, because I sweat a lot, because I'm training a lot, therefore I need more sodium than the general population who aren't doing that training. That's where the evidence doesn't really support that. And mechanistically, the reason for that is that we have kidneys and our kidneys are very good at sort of ironing out all the lumps and bumps, both in fluid and sodium intakes. ins and outs. So for example, obviously when we sweat, we're losing water, we're losing electrolytes, primarily sodium, although we actually lose proportionally more water than sodium. And that goes to, you know, what happens to the body during exercise. But as a result of that, our kidneys sort of handle that when we're not exercising and to a small extent when we're exercising, but the sweat glands do that sort of the heavy lifting during exercise. And so once you add a lot of training into the mix, what's going to happen is you're losing a lot of that during exercise. But we've shown, you know, there's a couple of good examples now showing this, and one going all the way back to the 1950s showing that your kidneys are very good at kind of ironing out the lumps and bumps from what the sweat glands are doing during exercise. And I wrote a paper around this called sort of Leaders and Followers, and the fact that the— during exercise, the sweat glands are essentially the leaders. And the reason for that is that we want to sweat To get rid of body heat that we're producing during exercise. And so we don't really want to compromise that ability to get rid of body heat. So the sweat glands will just do what's required for that purpose. That's going to include losing some sodium along the way. There is actually a mechanism in the sweat glands to retain some of that sodium, which is why proportionally the water loss and the sodium loss are different. And then once you stop exercising and sweat, sweating stops, the kidneys are then going to take over as they normally do. And, you know, restore things back to normal. So if you have very large losses, like we did a study where we got people running in the lab at Monash Uni here in Melbourne for 5 hours in the heat, they lost about 5,500 milligrams of sodium over that time. And in one trial, we gave them salt capsules, and in the other, we gave them placebo capsules. And in the group, or in the trials where they had the placebo capsules, we saw very clearly that the kidneys were able to not fully compensate within 24 hours, but Compensate significantly for this large unreplaced sodium loss that happened during exercise. So in the 24 hours afterwards, the amount of sodium that they peed out in their urine reduced by about 2/3. Now that wasn't enough to completely offset the loss, but again, you know, that's an unusual situation where you get someone exercising for 5 hours with literally no sodium. And so, yeah, you could argue that that sodium deficit is a little bit contrived for the purpose of that research study. You probably wouldn't have that large a sodium deficit in, in the real world and certainly not advocating that people avoid electrolytes during exercise. But we'll get into the nuances of that, I'm sure. But definitely the kidneys are very good at ironing out those lumps and bumps. And another study that we've done was deliberately having very high, very low, or normal sodium intakes for the 3 days prior to exercise. Because I think, you know, if you go back 10 or 15 years, there was often this assumption that if I'm a salty sweater, I need to quote unquote load up on sodium in the few days before my Ironman or 70.3 or whatever it is, because I'm going to lose a lot. And we showed that basically if you do that, you actually sweat more sodium out during exercise as a result. That the difference wasn't massive. We're talking sort of 10 to 15% greater, but there is still a difference. And so both the sweat glands and the kidneys are highly adaptable to differences in sodium intakes. And then the kidneys respond to the sodium losses during exercise by adapting to the urine losses that happen after that.

So just a little brief summary. If you think that you're a salty sweater, as the term you used, and some of the examples are if you wear a black uniform, you can see a lot of salt patches on your body, that would be an indication that there's some salt coming out with the sweat. Does that mean that if you actually increased your salt intake prior to the exercise that you could be a salty sweater just because of that action of Increasing the sodium, and you may not be a salty sweater, you, you could have brought that on by overloading with the sodium?

Look, I don't think it's going to be, from what we saw in our study, it probably wasn't enough to, I guess, put someone from quote unquote kind of normal to extremely salty sweat. Again, the difference was maybe a 10 or 15%. So it's probably not going to take you from Mr. Average to the extreme end of the spectrum. It will increase it a little bit, but not that dramatically. And we deliberately did a 3-day intervention because we'd done a survey of athletes and said, well, you know, if you are going to do this practice, how long before an event would you do it for? And most people said around 2 to 3 days before their event. Some people actually doing this up to a week before an event, actually loading up on sodium. Some people are not doing it at all, of course. So we thought that 3 days was a reasonable sort of compromise and sort of hit where a lot of people are at kind of practicing.

So your summary and advice is that it's not that valuable to load up prior? Yeah.

Yeah, no, I don't think so. The reason for that is, again, our kidneys are very good at adjusting to differences in sodium intake. So the vast majority of that sodium you load up on, quote unquote, in the few days before, you're gonna have peed out all that extra sodium before you hit the start line anyway. The one exception is maybe the last few hours before exercise, but you certainly don't need to do it for 2 or 3 days beforehand because you're just, it's just going to go in one end and out the other and you're no better off than when you started.

I want to focus on this point because to me, that study is mind-blowing. It's one of the, it's one of the many points that you're going to make and that I've read from you that kind of really rocked my reality of, of, of sodium and electrolyte replacement because That example, you know, you've literally taken athletes doing 5 hours of intense sweating and the body kind of just, in, in layman's terms, just sorted itself out basically regardless of, of, of what the intervention was. Did that, did that shock you as much as it kind of shocked me hearing it at the time? Um, and then, yeah, go, go, go for that.

Yeah.

Uh, not, not particularly because as I said, there was a study right back in the 1950s. that had kind of come to a similar conclusion. Now, this study was a trial of a single person who I'm pretty sure was the author of the study doing it on themselves. It was sort of self-experimentation. They did 48 trials as part of their PhD thesis back in the 1950s, and they saw a similar effect, obviously using techniques that are quite different to what we'd use probably in the 21st century. So there was that. There was also a PhD thesis from a student at Loughborough University in the UK who had seen something similar. It never ended up getting published. And I believe sort of talking to some of those guys since, there were some issues with calibration of some of their equipment that meant basically their data wasn't publishable in the end. But so for me, it probably wasn't a surprise because I'd seen indications of that previously. But that said, like when we were in the lab, obviously we're blinded to, you know, which trial the participants are on at the time. They're blinded as well. So we're getting these, you know, these bottles with the urine samples and we're measuring the sodium concentration of them. And the first couple, when we started that study, I sort of put them in the machine and the numbers came up. I thought, oh, there's something wrong with the machine. Like, I've got to recalibrate it because these numbers were the lowest I've ever seen, like just ridiculously low. And so we recalibrated it and tried again and they were still really low. And next participant comes through and lo and behold, the same thing. And it kept repeating and that the data was the data. So, yeah, look, I think I kind of had anticipated it, but when I actually saw it, in the lab on the equipment as we were measuring the urine samples, it really struck me how big that difference was or how aggressively the kidneys were able to kind of respond to that sodium deficit.

Yeah.

And so the natural thing that happens with just online information, online media now is, is our brains just want to jump to a conclusion and you hear that and you go, oh, well, the body does its job. You don't need to worry about it. And that is not the conclusion of this. And so can you explain what the conclusion kind of is, but where that doesn't quite fit with, hey, you do need some sort of intervention still, but at the same time, the body is quite good at sorting it out on its own.

Yeah, yeah, correct. So, yeah, so we looked at, um, we, we got the participants in that study to capture all their urine for the 24 hours after they stopped that 5-hour run. And so we could measure all the sodium that, that came out of the body since they stopped. They weren't exercising during that time, so there's no sweat loss. And so we could see that in, in both trials, we were providing all the food, so we knew exactly how much sodium they were consuming as well. So we could measure what we call a sodium balance. So the intake minus the output and see where it got. So obviously in that placebo trial, they had a, as I said, a 5,500 milligram sodium deficit at the end of exercise. And then the next morning, 24 hours after they started the exercise, we got them back in and we could, you know, see how much urine they'd lost in, sorry, how much sodium they'd lost in their urine during that time. how much they'd consumed and whether they were sort of back to square one as they were prior to the previous day's exercise. And they didn't get back to square one within that 24-hour period, but at the same time, we didn't give them a particularly high sodium diet during that period either. So for me, you know, they probably could have consumed a bit more sodium than normal. They probably would have got back there relatively easily. And, and as I said before, you know, that was obviously an extreme example where we got them going for 5 hours and deliberately withheld all sodium intake during exercise. And that's certainly not what I'd actually be advocating in the real world. It's not that you have to replace all the sodium you lose either. You can have some deficit, but the deficit is not normally going to be that big. And so the kidneys will have an easier time or be able to sort of bring you back to balance more quickly. And then I guess the final thing with that is, do you even need to be back to balance? Completely? Does that actually matter? Um, thinking about, you know, multiple hard days of training or a training camp or a multi-day event or something like that. Um, the short answer is we don't know for sure, but as I said, the kidneys and the sweat glands are very adaptable. So we would then expect to see the sweat glands starting to also adapt in the subsequent days of exercise and actually lower the sodium losses in sweat. So, yeah, overall, um, It's not saying, you know, deliberately avoid sodium. I don't think any of this is saying deliberately avoid sodium in that post-exercise period, but it's probably saying you don't need to replace every milligram of deficit that you finish exercise with either.

And what would happen if you attempted to do that? How impactful would that be on your performance?

As in if you did replace everything?

Yep.

Probably unlikely to make a huge difference at all, to be honest. What it may influence is the post-exercise rehydration, so the ability to sort of drink and retain water after exercise to rehydrate. Again, how important that is probably depends on what you've got the next day training-wise, or it's a, you know, multi-day race. And once you add food into the mix, that sort of muddies the waters a little bit as well. And that's pretty normal in the real world after exercise to, to eat solid food as well as take your, your fluid and sodium and things. So, yeah, look, I think at this stage, probably not, not a huge amount. Yeah, but, uh, you know, a clear study to sort of articulate that exact scenario you've described and measure performance at the end of that and definitively say yay or nay, as far as I'm aware, hasn't been done.

It's really great that you've actually, you know, gone into this so deeply because there's just not a lot of literature on this topic. And I'm intrigued as to what led you to this, uh, to this field in the first place, because there's just not a lot of information about it. And your study is one of the the more outstanding pieces of information that we, uh, that we get to, to actually use as an example. Um, yeah, what led you to, to study this in the first place?

Yeah, it was my work as a practitioner with Ironman athletes, actually. So you guys will probably remember back in, was it 2011 or 2012, when Ironman came to Melbourne for the first time? Um, you know, prior to that, obviously, there were plenty of guys, you know, traveling interstate or overseas to do Ironmans, but the number of people that were, you know, stepping up from 70.3 to the full Ironman distance just exploded here in Victoria because of that event. And I remember the first year, I can't remember, was it 2011 or 2012? I've forgotten now.

Yeah. Me too. I've forgotten as well.

One of the, one of them. But I remember that first year, like, the race was in late March. And I remember pretty much just after New Year's Eve, Like, as soon as January started that year, I just kept getting inquiry after inquiry after inquiry, and they were all asking for race nutrition plans for that first Ironman Melbourne. And so I was doing a bunch of them at the time. And at that same time, I'd built this little spreadsheet with sort of all the data from the various nutrition products. And so we could sort of, when we were planning out, okay, what are you having on the bike? We could go, oh, have one of those, 2 of those, and, you know, 3 bottles of that. And it would just calculate on the right you know, all the, the carbs, the fluid, the caffeine, and the sodium, because all that information was available for all the different products. And at that stage, we didn't really have any guidelines for sodium intake. And, you know, I included it in that spreadsheet just because we had the information available. It's like, well, why don't I just put it there? But I wasn't really targeting any specific amount of sodium because there wasn't any guidelines to say what number that should be. But, you know, every maybe 3rd or 4th athlete that I'd run through that process with would say, well, you know, what about this? You know, you've talked about fluid, you've talked about carbohydrate, we've talked about caffeine, but you've got sodium number on the screen there. What's that all about? I said, well, to be honest, we don't really know. Like, it's there, but it's in, you know, maybe it's interesting, but it doesn't, you know, I can't really give you an evidence-based guide around that. So for me, that was sort of a big kind of gap, just as you alluded to before, in our knowledge. And so I thought, well, you know, we need to do something about that. So anyway, fast forward a few years and I sort of left the job I was in at the time and came to Monash University to do a PhD. And unlike a lot of PhDs where the project is kind of funded and mapped out and it's like, okay, this is, you're going there to do this project. This was like an open-ended PhD. So essentially you're going there to do a PhD and do some teaching. But it's totally up to you what you want the PhD to be, which is quite unusual these days.

Right.

And so they said to me, well, you know, what do you wanna do? And I sort of thought back, and this was a, you know, a few years later, and I thought back to that scenario with all those athletes and not being able to give them an answer. And I thought, you know what? It'd be good to start to try to answer some of these questions that I'm seeing, but I'm not seeing anyone sort of try to work on coming up with any answers out there. So For me, it was like, well, there's a gap. No one seems to be filling it, so why don't I try?

Unreal. Who, who else in the world was leading the charge on assisting athletes in their sodium intake? Was there, was there anybody talking about sodium back then?

Not really.

No.

Even now, there's, there's not a huge amount. Obviously, there's a lot of sort of talk and hype, but in, in research terms, not really. It's been me and maybe one or two other people. Look, Gatorade Sports Science Institute had done a fair bit of work historically in that area, But a lot of their work at that time was really around perfecting the sweat testing process and trying to quantify sodium losses. And not to say that they didn't find—

Conflict of interest there as well.

Sorry?

A big conflict of interest there as well.

Yeah. Yeah. But I mean, but I mean, to be fair to them, like that work has been important. It's been really important. And, you know, I've used that in terms of the research methods I've then gone on to using in all of my work. But it was interesting to me that they were spending all this time on trying to quantify the sodium loss and not really putting any time or resources into Okay, once you know that, what do you do with it? And that was the bit that as a practitioner, that's what I wanted to answer. So yeah, I'm not saying that that work was not relevant or didn't contribute. It's contributed enormously and it's been really helpful, but it was only one part of the puzzle, I suppose, and no one was really looking at the other part. So that's where I thought, well, maybe I can have a crack at that and see what we can do.

Are you surprised Then watching endurance performance athletes, and probably we're talking anything over— if we're talking triathlon, anything over 70.3 and above, which is Ironman or Double Ironman. Ultramarathon. So marathons, for some marathon runners, it is 5 hours or, or more.

Mhmm.

So we can't just say it's just ultramarathon. Endurance cycling. We have a lot of endurance cycling events that are over 4 or 5 hours. So the time seems to be quite important for the sodium conversation. So where do you think that line is and how influential should it be under that line? And your comparison about talking about what's needed over that timeline that you think the sodium conversation needs to have a really high place. In your preparation plan for the ultra endurance events that we're talking about? Yeah.

So I'll take a step back to sort of answer that. I guess where I sort of started coming at this from was, why are we taking sodium? Like, what's the actual purpose? If we don't know why we're taking it, then what are we doing? And so the first step was to try and answer that. What are all the different reasons that you, that sodium may theoretically be helpful? And then what is the evidence that that any of those are actually true. And so I sort of started working through those one by one, either from a research point of view or reviewing existing research. But for each of those, also thinking not only is sodium helpful, but how much sodium is helpful and what information do you need to know to figure that out? Do you need to be able to measure your sodium losses to answer that question, or is it based on something else? And so there's a whole bunch of different reasons and we can get into some of those there. Different before and during and after exercise. But the, the during exercise piece, I guess there's probably a couple of main ones where the evidence probably suggests a potential benefit. One is if sodium drives you to voluntarily drink more fluid and you need to drink more fluid because obviously overhydration could be an issue as well. But in situations where you do need to drink more fluid, if consuming sodium drives you to drink more, then that's probably a helpful thing. But the benefit here is not really directly caused by sodium. It's sort of an indirect benefit. The sodium's driving you to drink more and the extra fluid is the thing that's actually helping you. And that probably isn't really driven by a need to measure sweat sodium losses. It's probably a combination of, you know, the saltiness of the drink, how that impacts your sort of thirst perception and just whether it changes the flavor of what you're drinking in a way that you like it. If you don't like it, you're probably not going to drink it as much either. So, you know, drinking is still a behavior. It's not just purely physiology. So that's, that's one part of it. But the bit you're getting at is more around, I guess, managing or trying to maintain stability in your blood sodium concentration. So the extremes of this would happen if we were severely dehydrated on one end of the spectrum. So that comes back to what you're talking about before, Jordy, where as you sweat during exercise, you lose fluid and you lose sodium, but you actually, the sweat glands recapture some of the sodium. And so as a result, your salt, your sweat is always less salty than the fluid that it originated from, which interchanges with the blood. So what happens is as you get dehydrated, your blood actually becomes saltier even though you're losing sweat, losing sodium, because yes, you're losing sodium, but you're losing even more fluid. That tends to make us thirstier. It tends to reduce urine output, et cetera. So that's one end of the spectrum. And I guess the extreme example would be if you went out and exercised and drank nothing. The other end of the spectrum is obviously overhydration where you're drinking too much fluid, more than what you're losing. And pretty much any fluid that's palatable to drink is gonna be less salty than your blood. And so as a result, you know, you're gonna be diluting your blood. So the blood sodium concentration's gonna fall, and that's what we see with hyponatremia. So they're the kind of the two extremes of the scale. But what I was kind of interested in is where's the tipping point between those two extremes? So at what stage does blood sodium stop going up from a fluid deficit and start going down? And then does that happen before you actually overconsume fluid? And, you know, using some mathematical modeling that's been around in sort of clinical medicine for a long time, The answer is yes. It's at about the 70% fluid replacement-ish, a bit lower if you've got very salty sweat and a bit higher if you've got very sort of low sodium sweat. And so from that, you can then kind of model out, well, in what scenarios is this actually likely to happen where you need to replace more than 70% of your fluid losses to prevent dehydration, you know, losing more than about 2 or 3% of your body weight Through fluid during exercise. And that's kind of where that 5-ish hours comes from. So up until that point, it's very unlikely that you're going to need to replace more than 70% of your fluid losses. Or even if you do, because you have a very high sweat rate, you're probably in a scenario where it's not going to be practical or tolerable to actually do so. You think about someone running a, probably a sub 2.5-hour marathon, for example. Well, they might lose 5% of their body weight during that marathon, but there's no way that they're gonna be able to drink enough fluid to stop that from happening realistically in warm conditions. They would lose more time slowing down to consume that fluid or from probably issues with tolerating that fluid than they would gain from actually being better hydrated. And so that, yeah, that's sort of where that 5 hours comes from is sort of, I guess, that theoretical tipping point with blood sodium concentration and then that combining that with the practicalities of, well, how much fluid does that actually take and is that actually feasible in the real world?

So practically, just thinking about this for athletes, 'cause we, we, we tend to think in terms of like, yeah, liters of fluid loss and, and now it's very common to, to, if you were to get a sweat test, um, to get the total fluid loss, but then get the, the salt concentration of that fluid. Let's just say for ease sake, you're losing Um, a liter an hour or so. Um, you're saying that 70% threshold, what is important to replace? So you're replacing, trying to get in 700 mL of water an hour back in if the event is around that 5-hour threshold. Is that the practical kind of takeaway you're saying in line?

Yeah. Yeah. And the longer the event goes, the higher that percentage that you need to replace becomes. It's just the relationship between, because if you think about it, like We talk about whether we use 2% or 3% body weight loss. That's a whole podcast in itself. We won't get into that today. But either way, 2% of your weight at the start is a fixed number, whereas the amount of fluid that you're losing over time obviously continuously increases the longer the exercise goes on for. So the percentage of that that you need to replace to stay within that 2% is going to creep up. over time, or with, you know, greater total fluid loss. So someone doing a 24-hour, you know, 20-hour ultramarathon, they're probably going to have to replace maybe 90 to 95% of their fluid losses to stay within that 2%. Whereas someone doing a, you know, a marathon in 2.5 hours is probably only going to need to replace maybe 40 or 50% of their fluid losses to stay within that, that, that 2% body mass loss. So yeah, the duration has this sort of mathematical impact on, on all of this.

Can I just clarify that, that 2% you're talking about, just, um, is that a number if you lose greater than 2% body mass, you start to see a decline in performance or, or hydration safety? What was that 2% referring to?

Yeah.

Yeah. So that, that's right. So that's the theoretical rationale and there's been guidelines for decades around that, is that once you're sort of, you lose more than 2% of your body weight through fluid losses specifically, um, that's a bit of a caveat, particularly for more ultra distance exercise, cuz some weight loss will come from from other means, is where you may start to see declines in performance. There's been a lot of controversy and debate around that number over the years. Some people say, you know, that's an absolute truth. Some people say it's nonsense. Some people say it's, you know, more like closer to 3% rather than 2%. Some of the interesting stuff recently from a colleague over in the UK, Dr. Lewis James, has suggested that actually maybe in runners, that level, you can afford to lose a bit more compared to cycling. So it may be exercise type dependent a little bit as well. There's also an open question about whether you can build some level of tolerance to that over time as well. So if you repeatedly exercise dehydrated, can you get away with losing a bit more before performance is degraded? These are questions that we don't have good answers to at the moment, unfortunately. But yeah, so that's why I was saying before, you know, you could pick 2%, you can pick 3% depending on your, your, your personal opinion. And it may be different. You might pick a different number in running compared to cycling. But that's kind of where the premise comes from. Yeah.

Got so many questions here. It's hard to queue up, isn't it, Jordan? So, so you're mentioning the duration is a key component of your decision-making about how much to take. So how influential is intensity of the exercise and the temperature of the day contributing to making slight variations in your decision-making?

Yeah. So, I mean, I guess where the duration really has an impact is the total fluid loss. So we're not talking about liters per hour now, we're just talking about the total liters that you've lost. So, you know, going back to Jordy's example before of a liter an hour, over 20 hours, that's 20 liters of fluid loss, whereas in 2 hours, there's only 2 liters of fluid lost. Sweat rate obviously then comes into play here because the total sweat loss is just the sweat rate multiplied by the duration of the exercise. So yes, that will have an impact. But when you sort of look at it practically within the range of sweat rates that are kind of physiologically possible for the kind of exercise that we can actually sustain over a prolonged period of time, you know, you're probably talking anywhere from maybe 200 mL an hour in very cold conditions, sort of low-ish intensity. Up to maybe 2.5, 3 liters an hour at the very top end in very high-performing athletes, probably larger athletes, particularly for running, because, you know, your calorie expenditure, therefore your body heat production is proportional to body weight for running, whereas it's not for cycling. So that is gonna have some impact, but you're only looking at maybe, you know, threefold, fourfold difference, something like that within that range, whereas the duration can extend out a lot more. And so what you tend to see is that, yes, both are important, but the duration tends to predominate just mathematically over time.

And also, the longer the event goes, the intensity can't be the same as a 2-hour event as compared to a 20. So, so the intensity would be kinda moderating itself down. And, and if you're following the TriVelo method, you would be measuring your effort from the start and not spiking yourself so that you're, you're putting yourself in a deficit Anyway, wouldn't you?

Yeah, totally. And I guess the other thing we, you know, we talked about that 70% fluid replacement before. As the intensity creeps up, 70% of 1 liter is 700 mL an hour, but 70% of 2 liters, you're now looking at 1,400 mL an hour. So how many people could actually consume 1,400 mL of fluid an hour, hour after hour after hour during a 70.3 or an Ironman? It's going to be very challenging. And once you get over 2 liters, it's basically impossible.

And so what does that, so in that exact example, what does that mean? Um, if you are a person that, that has that higher fluid loss and you go into race and I'm gonna have 10 hours, is this where you practically go, well, 70% isn't achievable. We, we dial it back to 50% for that person. Is that, is that the conclusion?

Yeah. I mean, there's, there's a couple of things you can do about this, and I think this is where it's important to have some idea going into a race of what you expect your sweat losses might be. You know, even if you're someone who believes, you know, drink to thirst is, is absolutely fine as a, a strategy, if you don't know what, you know, how much fluid thirst is going to dictate you're gonna need, how can you plan for how many bottles you need, whether you need 2 bottle cages or 3 on your bike? You know, how many aid stations do I need to get fluid from and how many bottles, all that kind of stuff? Because it's fine if you're thirsty, but if there's no fluid to drink, you can't drink to thirst anyway. So there's still, in my opinion, still has to be some level of of planning involved. So yeah, I guess understanding that fluid loss is, is going to be really important. And I've forgotten the other part of your question, Jordy. Can you say it again?

Just, do you, do you decrease the ratio, that 70% number for a person that's higher? Yeah, yeah, yeah, yeah, yeah.

So yeah, I mean, I guess the first thing I'd be thinking is, okay, well, if I know roughly how much fluid I would expect to lose over the bike leg of an Ironman or in time marathon or whatever it is. And then I can calculate from that, well, how much fluid theoretically would I ideally want to drink if, you know, in the perfect world to maintain hydration? And then I can look at that number and say, well, does that look realistic or not? So that can be realistic in terms of actually access to fluid along the course and the ability to carry it. It could be realistic in terms of just being able to tolerate it from a gut point of view as well, particularly for higher intensity events like Olympic distance or marathon or something. Can I even like swallow that without choking on it when I'm working that hard? So, you know, there's some practical limits there. And so for me, those practical limits kind of dictate a lot of that. If it's a gut tolerance issue, that is partly trainable for a lot of people. So you can actually get your gut more accustomed to tolerating a larger volume of fluid if that is necessary. So, yeah, there are parts of this that can be worked on. There are other parts, practical limits that are just, they're practical limits. So that kind of dictates to a, to a significant extent, you know, how much fluid you're going to realistically be able to replace in an event regardless of whether it's quote unquote optimal or not.

What's the easiest way to measure your fluid loss rates just in training and, and Basically doing a day's training, whether it's a 5-hour, 3-hour, 7-hour day, and then measuring your weight afterwards. Is that the most correct?

Yeah. Yeah. So, so weighing before and after is still by far the easiest way to do it. A couple of caveats around that. Firstly, if you're eating a whole bunch of solid food, obviously that's weight gain that you need to account for in those calculations. So you've got to measure for that. If you want to measure just purely the sweat loss, urine loss obviously is a weight loss that you've gotta account for that as well. So you gotta account for those other ins and outs of, or, you know, things that will change weight in, in either direction. I guess the other thing that is a bit challenging with that is you can say, oh, I'm doing a, you know, 1-hour run today. I'll measure my sweat rate. But is that sweat rate actually relevant to race day? Well, that depends on the pace that you're running at. It depends on the conditions that you're running in. And so that can become quite challenging. And the example I often use is, you know, training here in Melbourne in the winter for a race in Kona in October. You know, we know that obviously your sweat rate in Kona is gonna be far higher than it is training through the winter here in Melbourne. So how are you actually going to measure your sweat rate and say, that's my sweat rate in Kona? You're probably not going to be able to realistically. That's where Some recent work by some thermal physiologists in Canberra and Sydney at the University of Sydney and the University of Canberra have done some really great work coming up with predictive algorithms to predict someone's sweat rate under different conditions. So you can go to sweatratecalculator.com and plug in your different variables there. And obviously, it's not gonna be perfect, but it's gonna give you a ballpark figure. Particularly, I think that's useful for those times where you can't really get a representative session in training of the sort of the pace, the conditions, etcetera, that you might expect on race day.

So sweat testing in itself, is that, is that something that is better than the, the advice you just gave then? Is it more accurate? And how impactful is it compared to an ultra compared to a 70.3? How useful is it?

Yep. So the sweat testing I think you're referring to is like putting on patches or some of the wearable devices that are now available.

Yeah.

So The idea behind the sweat patches is to collect a sweat sample and measure the sodium concentration. So it's not measuring fluid loss, it's the sodium aspect. And you actually need the other, like the weighing before and after, to combine with that data to actually figure out the sodium loss. The wearable devices is an interesting one. Obviously, just in the last probably 3 years or so, they've sort of come onto the market. I can think of at least 3 that are commercially available now. And so they will give you a number. We'll talk about whether it's accurate or not, but it gives you a number in terms of sweat rate and then sodium concentration. And again, it can combine those 2. So the sweat rate measurement using a wearable device, some of them will do it a little bit differently. It might just be measured based on the flow rate of sweat through the sensor and then using an algorithm to try and approximate what's happening over the whole body from what's happening at that one little site on the body. That is, you know, Gatorade has spent a long time trying to nut this out, and it is problematic to get accurate measures of sweat rate just from a single wearable device at a single site on the body because it is so variable across the body. I know one of the devices has tried to solve this problem by basically using an algorithm similar to the sweat rate calculator I mentioned just before in place of using the wearable device for the sweat rate component, and then they use the device more for the sodium I wanna keep, um, keep taking everything you're saying cuz it's just such brilliant, uh, information and keep trying to apply it practically to, to racing and endurance racing.

Uh, because, um, if I'm an endurance athlete, I'm sort of hearing, okay, well there's some mixed signals going on here compared to what we know. It's what you said before is, is so mind-blowing to me still that your salt concentration is actually rising with exercise.

Yeah.

Which is very different to what we believe. You're losing salt, so you need to replace the salt in. In fact, you're losing less salt than water all the time, and therefore your, your internal salt levels are rising. And so now you've said, okay, well, let's, for, for numbers sake, we've said that that 70% mark is kind of an example of what we use. If I'm an athlete, I'm thinking, okay, well, that's, that's good to know. I'm not trying to replace all my fluid loss all the time. Um, in that 70%, for example. Let's say again, using that practical example of 700 mL an hour, how much of that is just plain water and how much are we diluting that with any sodium and how do we try and get that right?

So yeah, unfortunately the maths isn't simple. So it's like in one of the papers I sort of draw it up as a table so you can kind of just look up the numbers in a table because it's not just a perfect straight line where you just go, you know, 2 times this plus that equals the number of sodium. Unfortunately, it's, it's more complicated than that. But, um, You're basically, once you start to rise above 70% fluid replacement, there's a need or potential need for some sodium replacement as well. Initially that starts off quite low. We're talking like 10 or 15% of the sodium loss being replaced, but as the fluid replacement starts to get higher, sort of up to 90% plus fluid replacement, and that generally tends to only be necessary. It's not to say people won't do it, but it's only really necessary and you're really pure ultra endurance, like probably even beyond Ironman type events. So more like your trail running, your 24-hour races, your Ultraman, that kind of thing. Once you get into that category and you're replacing sort of 90+% of your fluid losses, then you probably need to start to replace a much more substantial amount of your sodium losses. We're probably talking, you know, 60% to 80% or something like that. But, but neither number ever approaches 100%, and there's no literature anywhere that suggests that That anyone should or needs to replace 100% of either your fluid or your sodium losses.

And the, the reason we're doing this is because when you keep rehydrating, you are dilating the sodium level internally, aren't you? So we—

Correct.

Instead of dehydrating yourself dangerously low, you could be doing the reverse, which is flooding the body with too much fluid and getting that balance of sodium and fluid. And that's the key, isn't it? The balance of sodium and fluid. getting that right. And that could be the key to unlock all of the decision-making that you make is how do you work out if I've got that balance right? And I'd love you to talk about that.

Yeah, yeah, you're spot on. So obviously, you know, we said before, as you become dehydrated, your blood sodium starts to rise. But, and obviously if you drink plain water, it's having the opposite effect, it's going to lower it. And it's at that 70%, this kind of that tipping point where the lowering effect of drinking the fluid offsets the rising effect of the dehydration. And it starts to tip in the, in the other direction. And I think in terms of how we sort of think about this during exercise, historically athletes have, and, you know, sports drink companies and that sort of thing, the messaging has been, well, you lose a certain amount of sodium, certain number of milligrams, whatever it might be during exercise. And that's a lot. And if you don't replace it, bad things are going to start to happen. But the implication has sort of been, well, it's the losing the sodium that's important. Like you're getting a sodium deficit, quote unquote, and that, you know, that's going to be problematic. But I think what we've seen from the 5-hour study I mentioned, there are other studies kind of similar, but a little bit shorter than that, is it's the— just as you said, it's the balance between the fluid and the sodium that's important. So this is why the historical way of thinking about sodium replacement was based purely on what you lose. But now what we're saying is it's not only about what you lose, it's also about how much fluid you replace because the sodium and the water interact with each other. It's the concentration of the sodium within the water, the milligrams of sodium per liter of fluid. That's the important factor here. And so if we just replace the sodium, independently of how we think about replacing the fluid, and we're not thinking about the 2 things in tandem, we're completely ignoring this interaction. And that's where things can start to go wrong. Either we're replacing heaps of plain water and not consuming any sodium, and eventually, as I said, you pass that tipping point, the blood sodium will start to fall. And if it falls too much, you end up with hyponatremia. Or, you know, you can take a whole bunch of salt capsules, and if you don't drink enough fluid to balance all that salt you're putting in, you know, the reverse can happen and you make the blood sodium concentration even higher and that is problematic as well. So yeah, absolutely. It's about the balance between the two that we need to get right. And all the, I guess, the things that we can kind of attribute going wrong potentially during exercise, as well as the before and the during and the after, you know, pretty much all of that when we think about how we should think about sodium, it's always in relation to what's going on with the fluid. It's never—

Absolutely.

Mine in isolation from the other.

And it's such a good point. And a lot of the, a lot of the athletes, I feel, I don't know where this noise is coming from, but I've got a fair idea that, you know, social media, you can, you, we're talking here to one of the, the few people in the world who have actually gone into detail and studied this. And it always blows my mind that we're getting advice from people who actually haven't read any of your papers or don't understand any of the trials that you've done and are coming out with advice that's, that's a general, uh, not specific to each individual. And so it frightens me that people are on this bandwagon of, um, you know, it's almost like the carb discussion we've had where, you know, 60 grams was fine. Now 120 grams is seemingly okay. Um, so I worry that That salt, sodium, whatever you want to call it these days, is getting too high a priority when the kidneys does a fantastic job already. And as long as you keep the balance right, I'm trying to summarize here for the person who's listening to this because it is confusing. And it's taken Jordan and I a fair bit of research to get our heads around it. And even now, that's why we're asking you these questions because we're not convinced we understand. And getting that balance right and, and overtaking sodium has, as we know, really catastrophic outcomes for completion of your event because you could end up with a whole lot of issues, gut issues. And, and we've had athletes have that experience. And so getting that balance right is, is almost the key to it and not making it all about sodium, but making it all about getting the hydration so your sodium levels stay balanced and the kidneys not under such stress and trauma that it's lost control of your body. So you end up dehydrated so badly that you can't move, you can't actually continue the event, or being the opposite, which is too much fluid, and you are in a really serious state there as well. Can you just— am I getting that right?

Yeah, yeah, I think so. And as you said, it's tricky because that mathematical model I mentioned before to try and maintain that stability in blood sodium is not a a perfect sort of linear relationship where you can just have this one-size-fits-all rule. It scales depending on the amount of fluid that you've lost. So for longer events, you know, the situation is quite different to the shorter events. I've spent a lot of time trying to think about how we can make this into a simpler, more practical message that you can kind of just pull off the shelf and run with. I can imagine, yeah. I guess the easy part of that for me is if the event is less than 4 or 5 hours, it probably doesn't matter. You don't need a sweat test to tell you what to do because it's not gonna change what you do. And, and even if you do that, it's not really gonna make any sort of meaningful difference in the real world. It's not to say avoid sodium, it's just to say you don't need to be hung up on the specific amount. As the event gets longer, you need to start to think about that more. If you were to put a very rough number around it, and I emphasize that this is extremely rough, you know, that sort of 5 to 10, you know, say 70.3 up to Ironman, you might be thinking, well, you probably, for most people, only need to replace between maybe 20% and 50%. Obviously, that's a very big range of your sodium losses. And once you get beyond that, you're probably thinking, you know, 50% plus. But because it depends on your sweat sodium concentration, it depends on, you know, how much fluid you're losing and how aggressively you're replacing that fluid, it's hard to put an exact number on it. So, That's where, you know, calculators that do those sort of maths for you or that little table in the paper I mentioned before, that can sort of help guide you rather than trying to have this sort of one really easy rule of thumb.

The last 2 explanations are what made it really click for me, you know, in where you just say stop thinking about sodium in isolation and start thinking about sodium in how, what's happening in your blood sodium levels. In the body. And I think that's just been a little bit of a problem. And if you're confused hearing this episode, that's what Dan mentioned before, don't worry. We've, we've been very confused trying to wrap our head around this, this different way of thinking. And it's because the marketing and the messaging that we've had our whole life, basically since Gatorade's been around in the '50s, is you need to replace electrolyte loss and salt loss. And, and yeah, your message, Alan, is, is it's not quite that simple. It's, it's, um, stop thinking about sodium in isolation, but what sodium's role is with its It's, it's, um, balance in the body. And so thinking about, I wanna take it back to the 4 to 5 hour example because coincidentally, you know, a lot of 70.3 athletes at the top level are 3 hours 40, 3 hours 30. A lot of age groupers are between 4 hours and 4 hours 30. So it's right on that tipping point. And then, um, a big chunk are still 5 to 6 hours. So you're kind of saying there, don't worry too much about sodium loss, but these athletes are, at the end of 4 hours, you're bloody thirsty and you're, and you've generally lost a lot of fluid still and a lot of sodium. So yeah, what's, what's the guide there? Is it just kind of a bit more to thirst because it's not as relevant?

Yeah, I mean, it's not to say that you don't need to think carefully about your fluid replacement, but it's probably to say that the sodium replacement is not going to be as vital in that scenario. So yeah, you still want to think about, well, what are my fluid losses? How much should I ideally be replacing to try and stay within that 2, 3% sort of body mass loss, however you wanna kind of define it. But that's probably going to be less than 70% fluid replacement or, or just around that sort of mark. So the amount of sodium that you need to replace is, is quite low. And probably if you're consuming any product other than plain water, it's gonna have some sodium in it anyway. And so it's not like you're gonna be replacing zero. And so you're gonna be replacing some of it regardless. And that's probably all you need to worry about. And I guess if you're gonna manipulate the sodium from there, it may simply be, as I was saying before around taste. So if that, you know, you don't like the product or by adding a bit of extra sodium or electrolytes to something that you like the taste of it, it makes you want to drink more and you, you're someone who tends to underdrink during exercise, that's probably a good thing. It may also help get the carbohydrate in because often that carbohydrate is in the same fluid that you're drinking. So, but again, you don't need a sweat test to tell you what tastes good. So, yeah, from that perspective, it's sort of, you know, Do it based on personal preference. It's not until you get significantly longer that you need to get too worried about it.

Does carbohydrate play a role in impacting the absorption rate of sodium? Too much carbohydrate influence it and not enough carbohydrate allows sodium to be more manageable. Is there, is there any studies done that can link a relationship between them?

Yeah, there's a little bit. Probably the findings would suggest that the, the sort of the interaction between sodium and, and the glucose component of carbs in particular and water and how the 3 of those sort of work together in terms of the absorption is probably more relevant at very low carbohydrate concentrations. So this is probably a bit more important when you're thinking about the sort of the hydrolytes and the things that are used in more the clinical environment, which are quite low carbohydrate It's there simply for the fluid, not for the, the fueling aspect, where having the combination of a little bit of glucose and the, the sodium probably does interact. But once you start to get up to higher concentrations of carbohydrate, that effect kind of washes out and it probably doesn't really make a major impact. So, you know, these days with, you know, your Mortons and your Beta Fuels and things, you're up to 16% carbohydrate rather than your traditional kind of 6 to 8. No, I don't think it's gonna make a huge impact one way or the other.

What's our purpose here? You know, we're, when thinking about fluid replacement and sodium replacement, are we just trying to prevent a negative happening rather than thinking about performance benefit? We're just trying to prevent too much salt, which can cause its own issues, or hyponatremia, which is too much water, just to make sure we're staying in that window that's safe for the body compared to, I know your paper has suggested that, you know, staying in a hydrated range, we don't even know if that actually improves performance. It's just, we're trying to stop something unsafe happening. Is that correct?

Mm-hmm.

Yeah.

So there's probably 2 parts to this. One is sort of a direct effect and one is an indirect effect. I think we've got, I wouldn't say there's heaps of evidence, but we've got reasonable evidence, albeit a small amount of it so far, that sodium doesn't have a direct effect on performance. So from that point of view, you could argue it's, as you said, more around the safety side of things in maintaining a normal sort of blood sodium concentration. If it goes too high, you're going to be terribly thirsty. If it goes really high, you're gonna feel nauseous and stuff. Too low, you've got hyponatremia. If that gets too significant, that can be potentially dangerous. So there, there is the safety aspect. I, I think there's still potentially an indirect effect from sodium. As I said before, you know, if it impacts on how much fluid you drink and that impact is a positive one in terms of ending up with a level of hydration that's more appropriate or more optimal, then that's potentially a good thing. And there are some studies Looking at the effect of sodium on performance, and most of them don't find any positive effect. The one that did was actually during an actual 70.3 in Spain where they gave people, they divided them into 2. So it wasn't a crossover trial, which is more typical of what we do in the lab. So they gave half the people in the study salt capsules and the other half placebo capsules. They did their 70.3 and they just simply looked at the finish times. And they're about, I think, 7 or 8% faster when they took salt capsules, or the group that took the salt capsules were 700% faster than the group that took the placebo capsules. But the one thing that really stands out in that study is the group that took the salt capsules also drank more fluid. And I think if you look at the lab sort of mechanistic studies and how that sort of translates to what we're seeing in the field-based studies, it's almost certainly probably the extra fluid that was consumed that actually improved performance. Whether that extra fluid consumption was coincidental or was driven because they were having the salt capsules, a little bit harder to say. Some studies show an effect, some don't. But if it does drive you to drink more and that's appropriate, then that's potentially an indirect way why sodium could improve performance. But again, you don't need a sweat test to tell you that.

That's a great answer and really helpful. And of course, you would probably not have control over exactly what every piece of fluid that athlete was taking in that race. They could be grabbing stuff from aid stations, which has got a mixture of different things. So that's the difference between a field test, isn't it, and a lab test.

And it's also self-report. So they're asking them at the end, well, how much fluid did you drink, as opposed to how much you spilled or sprayed on yourself or whatever it is, how much carbohydrate you consumed. They also asked them that after the race. And then, you know, in a 70.3, You know, as much as, you know, you're not meant to draft, there's potentially some drafting effects for some people. There's, you know, someone had a bad transition or their shoelace came untied or something like that. You know, so many variables, all of those things affect the finish time, which was the outcome measure in that study that you can't really account for. All you can do is just try and get more and more participants to try and sort of average out the effect to minimize the risk that any of these little variables are influencing the end result.

I wanted to ask a question a little bit about what I've seen in the last, since I've been doing triathlon since my very first one in 1981. And I've really watched with interest how things have come and gone. And this is popular, and now it's not so popular. And sodium seems to be the latest one that I've been really intrigued as to watch as to how and how things are developing in this field. And, and I think a lot of the things that have happened From the early days to now are absolutely brilliant. They're great technological advances, and all the athletes have benefited from really sound advice. The sodium one to me is quite frightening because I see athletes chugging down salt tablets upon salt tablets, and, and I'm asking myself, is there some, some information that I'm actually missing here? That's giving these athletes the, the okay to do this to themselves. And, and then what effect is it having on their performance? And, um, and from my own logical way of thinking, we're just trying to keep our body balanced so that we're not actually inhibited from performing properly, rather than trying to get an advantage. And everything we do these days is, is this an advantage to our performance? And I think Me seeing athletes chugging down these salt tablets every hour for 1,000 milligrams of salt every hour, I'm just, I'm perplexed, bemused, flabbergasted. I, I'm, I'm just so intrigued as to what you think about what you're seeing. Yeah.

No. No. Totally agree with that. You know, all these things tend to be cyclical. They come along and they become popular for a few years, and then they kind of fade away and something else comes along. And You know, when you're around long enough, they eventually come back again. You know, we see that with, you know, low-carb diets and, and all sorts of things. And, you know, the 2010s was all about the, the low-carb diets, and then the 2020s, it's all about the, you know, how, how many carbs can you stuff in during exercise? Um, you know, same, same with supplements that, you know, come and go and things. And I think, you know, electrolytes and sodium specifically is kind of having its moment at the moment. So Certainly not something I anticipated when I started researching in this field 10 years ago, that it will be such a massive topic. I thought if anything, it would probably sort of fade into the background. You're a good forward thinker.

Yeah, yeah, exactly right. What a great selection you've done.

Yeah, yeah, yeah. So yeah, I get a lot of podcast invites and conference invites and things now because of that, which I hadn't seen coming. So yeah.

Nice, Andy.

Yeah, yeah. So yeah, there's certainly that aspect, but you're right, like these things are always kind of cyclical and, you know, a few of them prove their worth and stick around. But if we think about dietary supplements more broadly, you know, the Australian Institute of Sport supplement framework kind of grades the evidence of all different supplements and they have their different categories. And you typically, like consistently over about 30, I think the supplement framework's been going for almost 30 years now, 25 years. And, you know, there's consistently the 4 or 5 that have that, that stay there and the others sort of come and go. And the ones that stay there are like your creatine, beta-alanine, sodium bicarbonate, caffeine.

Beetroot juice.

Beetroot juice there to some extent. But then, you know, a lot of those have very specific use cases as well. So they're not universally applicable to everyone in every situation either. So yeah, there's 4 or 5 that tend to stay there. And when you think about what they're doing, those supplements, they're not necessarily these like pills or potions that act almost like a, you know, with the exception of caffeine, that act like a drug that just miraculously boosts performance. All they're doing is putting in a greater amount of, or boosting up the store of a particular nutrient that is very difficult to get from just eating normal food. Like even creatine, you know, creatine exists in meat, chicken, and things like that, but you just have to eat a huge amount of those things to maximize your muscle store of creatine. Same with something like beta alanine. Well, you could eat 2 kilos of turkey a day for 8 weeks, or you could take it in supplement form. So it's just easier to take it in supplement form, but there's nothing kind of magical about those supplements. They're simply providing things that normally exist in food, just in quantities that are practically challenging to get. And, you know, sodium again is along the same lines. Like it's a nutrient that comes in normal foods. There's an amount that's full, there's an amount that's too much or not enough. Um, but it's certainly not gonna be any sort of magic solution to anything. It's not suddenly unlocking some biological mode that is otherwise switched off or anything like that.

I think, Dad, um, to your point about, you know, seeing the, just the nature of taking salt for sodium's sake, it kind of comes back to the very first point you made of the podcast, Alan, of, of generally day-to-day athletes and general population are getting enough sodium from diet. Um, and then we start to consider it once we've gone through this whole table of exercise intensity, length, et cetera. But it's kind of a bit of Occam's razor, um, with salt where, where we go for a lot of athletes, why are you feeling so sick in, in the Ironman? What's happening? Trying to dissect every, every single thing you're having. And Occam's razor is that the simplest solution is often, or the most obvious solution, or the simplest one is actually the answer. And it's, well, you're feeling sick because you're chugging salt tablets. You know, and we don't have to look any further than that. That's kind of what's happening. And so I wanna ask a question off that in terms of guiding to thirst versus sticking to a plan. Um, and we saw an example with Lucy Charles-Barclay at the World Champs where going off thirst wasn't actually a very good indicator to her, even though we're kind of thinking that that's actually, most of the time it's actually pretty accurate. But in her case, for some reason she came outta the water insanely thirsty and she could just not get enough fluid in. She was going way over what she normally does because in the bike she's going, I'm really thirsty. I think I need more water. She ended up hypernatremic. So, so going off thirst and trusting your body signals versus a plan, where do you try and give some guideline around that?

Yeah, you know, really great point. And I think for me, this is where, you know, even if you prescribe to that kind of drink to thirst notion, you still need to have some level of assessment of where things are at. And, and just as you said, Jory, like There are people that quote unquote drank to thirst and ended up hyponatremic. And there are people who quote unquote drank to thirst and ended up quite significantly dehydrated. So I guess when I'm working with athletes, the thing I'm trying to figure out is, is thirst a good guide for that person? And the way I would normally do that is if we go out and do that sort of fluid balance test where you weigh yourself before and after to work out your sweat losses, there's some additional things that you can add to that that really help answer this question. So one of them is firstly measuring the fluid that you actually consumed. So you're measuring not only what you lost, but what you put back in. But also, you know, rating your sense of thirst on like just a simple 0 to 10 scale. So 0, not thirsty at all, 10, like you've been lost in the desert for a week kind of thing. Yeah, at the end of the session. And also your gut symptoms from, you know, 0, no symptoms at all, to 10, like the worst imaginable sort of gut symptoms. And that additional information of the thirst and the gut symptoms to me, oh, and sorry, the final thing is the fluid that was available versus the fluid that was consumed. Because you can do that sort of fluid balance test and you can do all that and say, oh, this person continuously gets dehydrated. They're not drinking enough fluid. Okay. That's nice. Why are they not drinking enough fluid? And so that extra bit of information starts to help answer that question. So were they not drinking enough fluid because they just weren't organized and they didn't carry enough fluid with them? They didn't realize how much they needed. Well, that's just a logistical issue. You can solve that pretty easily the next session. Or were they not drinking enough because they were getting gut issues and they couldn't tolerate the fluid? Okay. Well, maybe they need to do some gut training. So that's a different solution to the same potential problem. Or the third one is that they just didn't feel thirsty. So they didn't drink much because their sense of thirst didn't tell them they needed to. And so in that situation, you know, it's easy, easier said than done to sort of recalibrate your sense of thirst. Maybe that's possible for some people, but it might be then flagging those people where maybe thirst is not the best indicator because, as you said, it's driving them to overdrink or underdrink during exercise for whatever reason. And so, yeah, those extra bits of contextual information, I think, just give you so much more value from that sort of testing that you're doing and can help answer some of those questions. So when you get into that situation, then you can sort of start to plan for race day and say, okay, well, I'm someone who knows that thirst is probably not a great indicator. It tends to drive me to overdrink or underdrink. So now I need to have a bit more of a plan in terms of, well, how much is about right? Knowing that, you know, every day is going to be different, you know, whether it's a headwind or a tailwind, or whether it's 5 degrees warmer or cooler, or 10% greater or lesser humidity is all going to impact To some extent on, on that equation. And so I can have the perfect plan. It's never gonna end up perfect in reality, but at least it gives me a bit of a starting point. And then from there, I need some sort of way. And I think particularly in ultra endurance stuff, when you get into your ultra trail running and things like that, I think at some stage you kind of have to rely on thirst a bit, cuz you're not gonna whip out a set of scales in T2 and measure your weight and see where you're at. So you're gonna have to use thirst because it's really the only sort of dipstick, if you like, we've got mid-race of, of where you're at. And, yeah, I think all the wearable devices wanna come up to the point where, you know, it's telling you where you're at without actually measuring it. But, again, unless it can measure the fluid inputs, just measuring the outputs is not necessarily that helpful. Yep.

Yep. I don't wanna, we're getting to the end of the podcast and I don't wanna open a, a whole new Pandora's box, but In terms of, we know that heat and thermoregulation has such an impact on performance. So where does that tie into just talking about kind of fluid and sodium, but as you're getting hotter and hotter in an event, how do, how does that tie into fluid re-intake and hydration? And, and we know that that definitely impacts performance, right?

Yeah.

So yeah, obviously as, as conditions get hotter, sweat rate is gonna be generally higher, either because Yeah, you just have more difficulty getting rid of heat to the environment as it gets hotter. If it gets more humid as well, the sweat doesn't evaporate as effectively to cool you down. So generally speaking, the need for fluid will be probably greater in those situations, and most people would kind of know that intuitively. And I guess that, that tips maybe that 70% replacement a little bit for those longer events, that, that may come earlier. If sweat rate is higher, where that 70% mark sort of falls, might be a bit earlier rather than a bit later. And so you might want to be a bit more aggressive. And I guess in terms of the way that fluid impacts on thirst, again, you might be thinking, okay, well, I'm going to struggle to consume enough fluid in this event in those hotter conditions because I know my sweat rate is going to be really high and it's just, it's a challenge for me. So again, maybe using a bit more sodium deliberately to kind of drive thirst and drive that fluid intake may be helpful from a sort of like a behavioral perspective there. So long as that the fluid doesn't get so salty that you're like, ugh, I'm not drinking this because it tastes terrible, then obviously it's having an op— having the opposite effect to what you're, you're trying to achieve.

I just had a super interesting self-anecdote example, which, um, I know is so multifactorial, but spending a lot of time staying and living in Indonesia more, um, when I first started trying to train the same way here, um, I had my own experiences of, of just Post-training feeling horrible, you know, and I, and I was really trying to get a lot of water in and setting myself a little bit hyponatremic because I was so thirsty post ridiculously humid training sessions. I was suddenly drinking 5 liters of water post-session and it was making me worse, you know, until I finally just clicked and went, what am I doing? Like, get electrolytes in. As soon as I did that, the feeling was better. And my amount of fluid post-training dropped of what I needed to feel Just better and actually better. And then I draw the conclusion that, oh, I need that after every session. Um, and then through self-experimentation and more thought process, uh, I kind of thought I got challenged on that thinking, well, is it the, is it the, um, sodium sachet that's actually making it better or is it just the fluid intake? And, and I had my own experimentation of finding, well, actually, yeah, my first signal was wrong after training. I went to 5 liters of water and that was too much. You know, but I actually can get away with, I just have 1 or 2 liters in the kind of 4 to 6 hours post-training. Even if it's not sodium, this shocked me, I feel the same. Because I was convinced that it was the sodium in the sachet that was making me feel better. It was actually, I don't know, and I don't know if that's exactly accurate, but I was kind of finding that if I had sodium, I feel great. But also I experimented not having it, but just drinking less water and not panicking about the thirst. And I actually kind of felt the same a lot of the time as well.

So I think what's happening probably there and this this is the same before and after exercise, basically just at rest, is if you consume a large amount of fluid quickly that, that gets absorbed into the body quickly, that's going to have that similar effect to what we talked about with hyponatremia, just not as extreme. And, and your body's able to offload it so it doesn't become hyponatremic. But basically you've got to dilute your blood sodium concentration and therefore the osmolality, which is— we won't go into that now, but that's going to stimulate your kidneys to produce more urine. And so You know, just drinking a large volume of plain water on an empty stomach in particular tends to result in urine loss where you pee out pretty much everything that you drank and sometimes even a little bit more. And I think this is where a lot of the, the kind of the science-iness behind the daily electrolytes sort of originated from, that once you add the electrolytes, you don't dilute the blood sodium as much. And so you retain more of that fluid that you consume. I think what you then experienced is If you deliver that fluid more slowly to the body, you're not getting that sudden drop and that dumping of the, the excess fluid via the kidneys. A similar effect is achieved when you add solid food into the mix. So not, not every situation, but a lot of situations, people are going to eat directly after training, a meal or snack of some sort. And once you start adding solid food to the mix, it slows down the emptying of everything from the stomach, including the fluid that you drank. And so it's kind of trickling in rather than rushing in, and you achieve the same effect. You actually retain it better whether there's sodium or not. But certainly if you are drinking fluid on an empty stomach, particularly a large amount of fluid, then yes, that's when adding sodium in particular will help with the fluid retention. We see that before exercise with the kind of hyperhydration strategies, but we also see it post-exercise with the rehydration. The concept is the same.

I guess that the takeaway is for the individual, you know, because not everyone feels like eating straight away, even though we know we probably should. But if you can just get a little bit of food in, you're probably getting some salt from there, kind of spacing out your hydration and not just chugging water like I was doing. Um, and then sodium in a drink could definitely help, but it's not necessary is, is what you're saying. Yeah.

Yeah. Yeah. I mean, and the, the faster you drink, the more you drink, the less solid food you've got in that mix, the more important the sodium becomes to help retain that fluid.

Dad, did you have any final questions? Kind of wanted to try and leave it.

I know, but it's probably not for this. I think we've Probably exhausted. Uh, I've got some other questions that are kind of related, and that's what I was kind of thinking about asking, but it, it might not be for this one, might be for another one down the track. But, but so just generally, do you have any, um, evidence to say that overconsuming sodium can lead to the gut intestinal issues, or is that a bit of guesswork and it could be a lot of things that are contributing to it? But Is sodium a culprit for this over, over, over excessive?

Yeah, it can be one of many. There's a whole range of things that can cause gut issues, particularly during exercise. We obviously won't get into all of those, but yeah, certainly dumping a lot of sodium, particularly in the form of sodium chloride, into the stomach quickly and without much fluid. So I'm thinking salt tablets or capsules that are like gelatin capsules that basically dissolve as soon as they touch any kind of water, definitely is a risk. And I'll leave you with a funny story about this. So when I was doing my PhD, we were using salt capsules to blind the study, whether we gave them a high or low salt diet prior to exercise. And I'd had a warning. I used to work in a hospital and one of my colleagues there had done a sodium study in diabetes patients. And she said, oh, you need to be careful with the capsules because they can cause nausea or vomiting if you give too many too quickly. So I thought, oh, I'll try this out. So we had some gelatin capsules lying around at the lab and I made some up with just normal salt and consumed a bunch of them. And 10 minutes later I was vomiting. So yes, certainly if you have a lot of sodium going into particularly an empty stomach with no water to dilute it very quickly, then yes, nausea is very common. And if it's severe enough, can cause vomiting as well. But usually when it's provided as part of food, like salty chips or something like that, you don't normally have a problem with that, even though it's a lot of salt. If it's within a drink, usually you don't have a problem, even if the drink is very salty. So it's typically more your salt capsules or tablets that are taken on an empty stomach where that might be an issue.

Yeah. That's great.

I'd love to finish off, just, just take one last bit of your time and, and kind of just hit you with some, some sort of general conclusions from your paper and you can tell me maybe one or two sentences if you think they're accurate or what still needs, needs research or so. And the first one is we focused on sodium. Uh, are we forgetting the other electrolytes and the role of potassium, magnesium? They're also marketed. Uh, what's, what's the conclusion there?

Yeah, I think the conclusion there is you lose so little of them in sweat that it's not really worth worrying about, particularly magnesium and calcium. Uh, you lose a little bit more potassium, but it's still pretty small. There's not a lot of research on the potassium replacement aspect of all this. It certainly is not going to hurt to have a little bit in your sports drink, but how necessary or not is probably still up for debate. But I think the calcium and the magnesium, like the amounts that you lose in sweat are so, so tiny that, you know, eat a handful of nuts and you probably replace more than the magnesium that you lost, or, you know, drink 100 mL of milk and you probably replace more calcium than you lost.

So, on that says, the conclusion is fair to say that athletes don't need extra supplementation day to day, and buying supplement drinks might be what's been called now expensive salt compared to what you can just get daily in your diet.

Well, there is some suggestion that a reasonable proportion of the population as a whole may be slightly deficient in magnesium, not to the clinical deficiency levels or anything like that, but could benefit from increasing their magnesium intake. Now, whether that comes from supplements Whether that comes from just eating higher quality food, um, you know, it could be either. Uh, but I think in that case, it's more about, it's more thinking about magnesium in the way you would think about maybe iron supplementation, not the way you would think about electrolytes during exercise per se.

Yep. Sodium loading, salt loading, uh, pre-race in the days before the race is pointless?

Yeah, pointless. Uh, unless it's, you know, coming back to what we were just describing before, unless you're trying to re— retain a huge amount of fluid to become hyperhydrated before exercise. And even then it's really only the last sort of 3 or 4 hours before exercise, not 3 or 4 days. Yep.

Yep. So we've spoken about this, but just to conclude, there's no evidence to suggest that sodium itself improves performance in any way.

Correct. Unless it's indirect via improvements in fluid intake.

We've discussed this a lot in our own podcast, but also people still believe that cramping is because of sodium loss and that's That's still a myth as well?

Yeah.

Cramping is incredibly complex. It's probably a syndrome with multiple causes between different people or multiple causes in the same person on different days. Hyponatremia can cause cramping, but there's no evidence that just a sodium deficiency, quote unquote, so the loss of just a certain number of milligrams of sodium over time, regardless of the concentration, has anything to do with cramping unless it became like Ridiculously extreme. And pretty much you couldn't do that unless you deliberately set out to do it. And even then it would be very difficult.

And then sweat testing, uh, does have its place, uh, but it's important to get the context right of, of, of how and, and how, how am I using it?

So sweat sodium testing?

Uh, I guess, you know, a lot of the common, uh, sweat testing people are going into labs to find their fluid loss and their sodium loss. Yeah, yeah, yeah.

Yep. So the fluid loss aspect of the testing, the weighing yourself before and after can be incredibly useful. The sweat sodium testing, where you're actually trying to measure how much sodium is in your sweat, does have a place, but probably only, you know, the more ultra distance stuff. So in triathlon, it's probably Ironman Plus, and then, you know, well over 5, 6 hours of exercise, whether it's cycling, running, whatever it might be.

I hope a lot of those conclusions help the listener and the audience understand now with more context. We've just had an hour 15 minutes worth of context around sodium, and that's why I hope those conclusions now make sense. to the audience. And, and if they don't, if you've got any questions, let us know and maybe we can have Dr. Allen on for a part 2. But thank you very much for your explanations and your thorough research that you've done. You're literally one of the, probably the leading expert on sodium based on the work you've done. And, and, and yeah, in this time of information where, as Dad, you pointed out that it's so popular, this is a very, very helpful voice. So thank you for that. What's next for you in terms of your own research? What do you want to, what are you looking at yourself to try and, what questions are you still trying to answer?

Mm-hmm.

There's probably a couple that I think are kind of unanswered in this space. One is the form of sodium. So traditionally sports drinks were always sodium chloride, so your normal table salt, and that's the majority of sort of sodium that we get in our food and things. But over the last probably 10 years or so, a lot of products have moved towards using sodium citrate instead of sodium chloride, mostly for taste reasons. There may be some differences. So what happens if you replace all of the sodium you lose but none of the chloride you lose once you start to decouple those, because generally they move together in the body, particularly through the sweat glands. So, yeah, that, that's a bit of an unanswered question. I don't expect that there's gonna be anything dramatic to come of that because we haven't heard this sort of epidemic of problems that have occurred in the last 10 years since people have moved to mostly sodium citrate products. But it is sort of an, an unexplored area. So I think that's an interesting one. Both before and, and during exercise. So they're probably one of the main ones. Uh, like a lot of areas of sports science, certainly female athletes are underrepresented in the research in general. So it'd be good to see some more data in, in that context. Uh, and as I said, I think some of these, um, effects of sodium and hydration may be also dependent on the type of exercise. So running versus cycling as well. So a lot of the research is typically done in cycling because it's easy to do in the lab. easier to measure performance in the lab. You know, apart from maybe the, the Wahoo Kickr treadmill is probably the first, you know, like, self-paced treadmill. So we can get genuine sort of self-paced time trial performance measures in a lab. That hasn't really been possible up until this point. And so a lot of the sort of performance-based research has been restricted to cycling. So, yeah, having that in both running and cycling and seeing if there is a difference between the two, I think, will be useful. And just more performance research in general because, yeah, it is quite lacking. I sort of tried to find papers on that towards the end of my PhD. We could only find, I think it was 5 or 6, and a lot of them had sort of methodological problems where you're like, I don't really trust the result of that anyway. So, while there's not great evidence of a performance effect, it'd be good to have some really well-designed studies on that to kind of put that to bed.

Well, thank you very much for your time. It's been incredibly valuable. I know everyone will love Hearing this and just getting this information. So, uh, I know that I just recently found your own podcast, Fueling for Endurance. That's, that's the title, correct?

Or Fueling Endurance?

Yep. Fueling Endurance.

Yep.

Uh, that's going to be one of my new favorite ones, I think. So people can find you there. And then are you working with athletes still, or where else can people potentially find you?

Uh, no, I'm not doing any one-on-one work. I kind of stopped that about a year ago just because of kids and university work and other things like that. So I'm at Monash University. Um, so usually if you just Google my name and Monash, you'll find all the details there and all the publications and bits and bobs. I work with a company called Fuelim that make an app around sort of nutrition planning. So they do some one-on-one work with athletes, but most of my work is more the behind-the-scenes stuff in terms of developing the algorithms and things that sort of build the recommendations behind the app. So doing that space and then the podcast is pretty much the main things. And then my other work is more in the education space for educating dietitians.

Amazing. Well, thank you again for your time. We really, really appreciate it. And, uh, to the audience, thank you for listening, and we'll see you in the next episode.