Episode 14 - Do You Need Salt Tablets? With Alan McCubbin
Do You Need Salt Tablets? With Alan McCubbin
When it comes to talking about sodium, there is no better brains trust than Alan McCubbin.
Alan is also an Advanced Sports Dietitian who has spent hours slaving away in the lab during his PhD in the area of sodium and hydration for endurance sport.
In the latest episode of the podcast, we took a dive into what the research currently shows for sodium replacement during exercise.
- Why do we think sodium is important for endurance sport?
- If there are any guidelines around sodium replacement to guide us?
- Alan’s work in the sodium replacement and hydration space
- What happens if we don’t take on enough sodium?
- What happens if we overdo our sodium replacement?
- Does it matter what form sodium replacement comes in?
- In what situations would he recommend sodium replacement?
- Where does sweat testing fit in with all of this?
Plus so much more! If you are an endurance athlete, this episode is not one to be missed!
If you’re interested in understanding your personal hydration needs, book in for a Sweat Test with an Advanced Sports Dietitian today | Sweat Testing
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Episode 14 – Do You Need Salt Tablets? With Alan McCubbin
Taryn Richardson 00:06
Welcome to the Triathlon Nutrition Academy podcast, the show designed to serve you up evidence-based sports nutrition advice from the experts. Hi, I'm your host Taryn, Accredited Practicing Dietitian, Advanced Sports Dietitian, and founder of Dietitian Approved. Listen as I break down the latest evidence to give you practical, easy to digest strategies to train hard, recover faster and perform at your best. You have so much potential, and I want to help you unlock that with the power of nutrition. Let's get into it.
Taryn Richardson 00:45
Welcome to the Triathlon Nutrition Academy podcast Alan!
Alan McCubbin 00:48
Thank you. Thank you for having me.
Taryn Richardson 00:50
It's so good to have you. I can't think of anyone better to talk about sodium and hydration than you so thank you for joining me.
Alan McCubbin 00:57
Oh, pleasure. It's great to be here. Always good to talk about things that you spent a lot of time researching and things that you spend a lot of time thinking about.
Taryn Richardson 01:05
Yes, yes. Now I wanted you to help me answer the question, do we need to take salt tablets? That's the main thing that I wanted to talk to you about today. But I know we have to kind of take a step back from that, to understand that first. But before we do that, could you introduce yourself for those people that don't have any idea who you are and how you landed into being the sodium master?
Alan McCubbin 01:28
Sure, don't know about sodium master. Sounds like I've put salt on my food or something. Yeah, I've been an Accredited Sports Dietitian for about 17-18 years, something like that. I've worked in a variety of settings; private practice working with a lot of recreational athletes, but also elite and professional level. I've worked in academia. I'm a lecturer now at Monash Uni in Melbourne. I did my PhD there around sodium. So obviously what we're going to get into today.
Alan McCubbin 01:57
I've also worked for Triathlon Australia. So, I'm a consultant for them for their high-performance program. So, for their Melbourne based athletes for one of the Melbourne based coaches Danielle Stefano. So, I've been doing that for about three years now. So, it's good to sort of work through that whole kind of Olympic cycle and try and get those guys and girls to Tokyo for both Olympics and Paralympics.
Taryn Richardson 02:17
And how did you come to do your PhD in sodium?
Alan McCubbin 02:20
It's an interesting question actually. I already had one kid; child number two was not on the way at that stage. But I sort of thought mortgage, kid number one, PhD is probably not going to be financially viable. I sort of thought that opportunity kind of passed me by and I just happened to meet Ricardo Costa at Monash University, who had just moved over from the UK, actually, to set up the sports nutrition program at Monash and he sort of said, well, I need someone to help with the teaching side of things. Do you want to do a PhD along with that, and you can join us and do both? So, I thought, Oh, great, here's a role that's actually going to pay me enough to feed my kid and pay the mortgage and do some really cool research. This is one of the things I've always wanted to do so why not?
Alan McCubbin 03:03
It's often one of those things with a PhD project where the project is already there, and the topic and you come in to do the project, but in this case, I sort of walked in, and it was like, well, what do you want to study? So, it's pretty unusual, you get that kind of blank piece of paper to start with? So, I sort of looked at the literature and said, Well, what are the gaps in research? What are the things that we need to know a bit more about? So, you know, we know a lot about carbohydrates. We know quite a lot about protein. There's a lot of research in those areas, same with fluid to an extent.
Alan McCubbin 03:33
But sodium is one of those areas it’s kind of one of those big rocks of sports nutrition that people are constantly thinking about and testing and measuring. But when you look at the guidelines, there's very little there, and very little evidence to suggest, you know, what we should have in terms of sodium. So, I thought, well, that's kind of an obvious choice, from my perspective, in terms of what we can try and shift the dial on. So, you know, I didn't really have any preconceived ideas behind that. I didn't have a particular interest in sodium prior to that. But you know, six years later here, I am still working in that area.
Taryn Richardson 04:02
And that's why you're the sodium master.
Alan McCubbin 04:04
Something like that. Yeah.
Taryn Richardson 04:06
So, before we get too deep into some of the science, I think we need to set the scene around sodium and why sodium? Why do you think sodium is even important at all?
Alan McCubbin 04:18
It's a good question and I think there's different answers depending on whose perspective you're looking at it from, I guess. A lot of athletes, obviously talk about sodium and they think about sodium in terms of sort of how much seems in their products they're having, you know, drinks, gels, obviously, our question today is around salt tablets or capsules. So why is there sodium in all these products? Well primarily because when we sweat during exercise, sodium is the main mineral that we lose in our sweat during exercise, along with chloride. We lose a small amount of potassium. We lose a tiny amount of calcium, iron, magnesium but tiny amounts for those. So, it's pretty trivial, to be honest.
Alan McCubbin 04:55
So, by far the main one that we lose is sodium. We lose about 40 millimoles of sodium per litre of sweat. In contrast to that, you know potassium is only three or four millimoles per litre and, and you know, things like calcium are down to one or less than one millimoles per litre and the others are even less than that. So you can see how much greater the contribution of sodium is to the overall sort of electrolyte losses in sweat.
Alan McCubbin 05:21
I guess the other reason we tend to think about it is because when we look at what's in our blood floating around, we've obviously got the water component, but then we've got all the different bits and pieces the cells and proteins and enzymes and things, and then we've got the minerals or the electrolytes that are in there, and sodium, again, is the primary one that exists within that. So it has a big influence on the water. So the way the water moves around the body, but also how we either retain or offload excess water. Put all those things together and obviously, you're adding the fact that we're losing a lot of fluid during exercise and drinking a lot to replace. We're losing some sodium during exercise, obviously, and then, you know, potentially replacing that. So that's sort of how it all comes together and why sodium is the important one.
Taryn Richardson 06:05
So people have kind of run away with sodium a little bit. It's advertised really heavily to be in products, you know, certain things are high sodium, or sodium supplemented, but are there any guidelines around sodium replacement? And what we should actually be doing?
Alan McCubbin 06:19
Very little actually. I guess the main guidelines in terms of sports nutrition, there are others, but the main one that people tend to refer to is the American College of Sports Medicine. So their last publication was in 2016 and if you go to those guidelines, I can't remember it word for word, but there's a statement there along the lines of people should replace sodium when large losses occur, but they don't really define what a large loss is. They give a couple of sort of vague examples of that and then even then they don't give a quantified amount that you should replace.
Alan McCubbin 06:48
So you kind of walk away with those guidelines and think, well, I don't know what to actually do from that. I don't know when a large loss has occurred. I don't know how much I should replace. So you know, there's a been a lot said around sodium replacement and numbers bandied around in terms of how much sodium you need or doing the sweat testing process where you might go out and try and quantify that. And so you go out with the intention of replacing that sodium. But even when you do that, how much do you replace? There are currently no guidelines to tell us the answer to that question, even if we do the test.
Taryn Richardson 07:19
What are some of the things that you found in your work? Like, there's obviously no guidelines. That's kind of one of the things you've been working on. What are the main findings that you've discovered over the last 6+ years with your research in this space?
Alan McCubbin 07:32
So yeah, we've sort of looked at it from a few different angles. One of the first things we did is go out and look at what athletes actually think about sodium currently. So what are their current practices and how they think about it. That was interesting in itself. We found that, you know, the majority of endurance athletes tend to think that because they sweat a lot, they need to consume a lot more sodium than the general population on a day-to-day basis, but they had different ideas about how much and how to do that. Quite a few people said they'd deliberately increase their sodium intake, you know, for a few days before a major event, or up to five days, particularly the bigger events like an Ironman or ultra-marathon or something like that.
Alan McCubbin 08:10
The other thing that came from that work was, I guess, the way athletes tend to think that sodium works in the body and that is that they tend to think that we have like this big store of sodium in the body, like a certain amount. And then as we sweat, it depletes and once it depletes to a certain amount, you know, things are going to start to go wrong. Whether it's hypernatremia or cramping or something like that. So, therefore, we need to replace it to stop it getting to this sort of critical level where things are going to start to go wrong.
Alan McCubbin 08:36
Yes, there is a store of sodium in the body, but it doesn't really kind of work in that way. It's kind of similar to, you know, muscle glycogen with carbohydrates but the reality is that sodium is a bit more complex than that. It interacts with water and so we need to think about that interaction. There's a lot more to it than just the store and running out of a certain store. So we looked at that, first of all, to look at what athletes were actually doing.
Alan McCubbin 09:00
One of the things we were interested in was the relationship between how much sodium you eat on a day-to-day basis, and what that may or may not do in terms of the amount of sodium you then lose during exercise. So if you load up on salt for three or four days before a race, like a lot of people do, does that actually impact on the sweat sodium loss during the race? So you go out and do your sweat tests, you know, maybe a couple months earlier, and you come up with a number, whatever that is. Is that number going to be different on race day because you load it up with sodium? In other words, did the sweat glands adapt to that higher sodium intake? We know that definitely happens with urine and through the kidneys, but does that happen through the sweat as well?
Alan McCubbin 09:38
We found that yes, it does, but not as much as we expected, though. We went from a normal sodium intake and effectively doubled it. And yes, the sweat sodium increase did increase, but only by about 10-12% on average. Some people it was more than that, and some people it was less, but the average was sort of 10-12%. Likewise, we went to a really low sodium intake, and it dropped by about the same amount. So yes, you can push it in either direction by changing the amount of sodium in your diet. But it's not that big an effect at least over three days. What we're looking at now is more the sodium during exercise aspect of it. So we've got a study, which, unfortunately, is kind of parked idle because of COVID at the moment, and that's a running study looking over five hours of running and sodium replacement. But in the meantime, I've got on with some sort of mathematical modelling of sodium requirements during exercise, which has been really interesting.
Taryn Richardson 10:28
Yeah wow. So we're on the path to getting some good guidelines, hey Alan. We just need COVID to go away.
Alan McCubbin 10:33
I hope so. Yeah, I think there has been a lot of research in sodium, but a lot of it has been around sort of perfecting the sweat composition testing process. So a lot of the resources and research has gone into that, but much less work has gone into, okay, once you do that sweat test, and you've got your data, what do you actually do with that? Or even if you need the testing in the first place?
Taryn Richardson 10:53
Yeah, I would like to pick your brains on that. Because I think that is really important for people to understand. We haven't talked about this, but I've seen a company doing a sedentary sweat test where you sit down, you're not exercising, and they put a patch on your arm and it heats up, and then it makes you sweat underneath that patch, and they give you your sweat sodium concentration based on that.
Alan McCubbin 11:13
Yeah, that was designed originally for diagnosing people with cystic fibrosis actually. It's been around for several decades, because people with cystic fibrosis have a genetic mutation so their sweat glands don't work in quite the same way. So they get a much higher loss of sodium in their sweat compared to normal people. So yeah, so you do that test, and you will get a higher value compared to people without CF. But in terms of whether that's valid during exercise, I've never actually seen a study that's validated that to show whether the sweat loss from that method reflects what's actually going to happen during exercise.
Alan McCubbin 11:47
I suspect the answer is no, partly because when you do the patch tests sitting around, you apply the pilocarpine, which is the medication you add to make the body sweat, you can actually change the sweat rate by adjusting the amount of pilocarpine you give. And we know that the sweat rate actually affects the sweat sodium concentration. So if you apply more or less pilocarpine, you'll get a different result. But similarly, during exercise, you go out for a ride and depending on the sweat rate that will actually drive the sodium concentration. And that's one of the biggest influences on the sweat sodium concentration itself. The higher the sweat rate, the higher the sweat sodium concentration as a general rule, but as I said, you know, diet will have an impact as well. So you know, if you have a very high or very low salt diet that will change the baseline up or down a bit as well.
Taryn Richardson 12:32
Yeah, awesome. Thank you. So you've done some research in athletes practices and what their current thoughts are and thinking around sodium, and then also your sodium intake in your day-to-day diet and how that affects then your sweat sodium concentration when you do exercise. So in as little as three days it does affect your sweat sodium concentration, but not that much like 10-12%.
Alan McCubbin 12:56
Yeah, exactly. Not enough to really go Oh, jeez it's gone really high, or low. 10% difference is not really going to be that meaningful in the real world.
Taryn Richardson 13:04
What about for an Ironman athlete though that's potentially doing something like Kona? A lot of those guys sodium load once they get to a hot environment, and they increase their urinary output and potentially increase their sweat sodium concentration as well. Would there be many implications for an athlete like that, that's out there for 9-10 hours in the heat?
Alan McCubbin 13:23
On sweat sodium concentration, I'd still suggest no. A 10% difference like Ironman 10 hours plus, you know, is that going to add up over time? Is it going to be important? I'd suggest no, because when you have a day-to-day variance in sweat sodium concentrations that can be over 10% anyway. So yeah, like I don't think that's outside the normal variance you would kind of expect from one session to the next. Kona this year vs Kona the next year. So I don't think that difference is important.
In terms of the loading up on sodium in the days before and what that does. Is it helpful? The vast majority, like 95% plus of the extra sodium you consume is going to be peed out in the days before exercise, because that's what the kidneys are designed to do. So you know, people think about sodium in terms of loading up and yes you will store a little bit, but the amount is pretty small. And to be honest, you can achieve the same thing in the two or three hours before exercise. You don't need to do it, you know, for two or three days to get that same effect.
Taryn Richardson 14:18
Yeah excellent. Is there any other sneaky work you've got underway that we can talk about?
Just the five-hour study, as I said, that sort of halfway through at the moment, which has been sort of COVID interrupted. Probably the mathematical modelling stuff is the stuff that I'm really interested in at the moment. So that's taking some equations that were designed originally for giving intravenous fluids in hospitals to work out, okay, so if someone comes into the hospital and they've got a really high blood sodium concentration, or a really low blood sodium concentration, and that can be for various different reasons that have got nothing to do with exercise. How much fluid do I need to give them? How much salt do I need to put in that IV fluid, to get them back to kind of a normal blood sodium concentration? So it was designed originally for that purpose.
Alan McCubbin 15:04
12 years or so ago, some researchers looked at that in the context of exercise. And they found that, you know, as long as you aren't over drinking during exercise, it is actually a pretty good indicator of what's going to happen during exercise and using sweat sodium losses rather than your urine losses. So what I've been doing now is applying that equation and kind of flipping it around because the original equation says, Well, I'm going to put in what my blood sodium concentration is now, how much water am I drinking? How much am I peeing out? How much sodium and potassium am I consuming? How much of that am I peeing out? And what does my final blood sodium concentration look like?
Alan McCubbin 15:40
So I've kind of flipped that around and said, from an exercise point of view, what we're really aiming for is to have the same blood sodium concentration at the end of exercise as what we had at the start without having to tap into those stores that I talked about earlier. You can rearrange the equation, so you can say, Well, we've got a certain amount of fluid loss from sweat, we're drunk a certain amount with a certain sodium loss, which we work out from a sweat test.
Alan McCubbin 16:04
Then the other part of the equation is the sodium intake. So we can use that to be the part that we want to know. So, you know, we can rearrange the equation and say, well, under the conditions of this scenario, how much sodium do I need to consume or replace, to maintain a stable blood sodium concentration? Because as far as we can tell, really, the only bad things that can happen from a sodium point of view is to do with that concentration, you know, particularly when it goes low in terms of hyponatremia, rather than the body's normal level of sodium depleting per se.
Taryn Richardson 16:35
Wow, that's so exciting. So nerdy and so exciting.
Alan McCubbin 16:39
Yes, yes, ended up creating up all these three-dimensional bar graphs, which are a bit trippy.
Taryn Richardson 16:46
How far away do you think that is? Having that finalised in a way to be able to really sort of give it a good crack?
Alan McCubbin 16:51
Oh, it's ready. So the Sports Dietitian's Australia conference is on a couple of days’ time from the time of this recording. So there's a poster there that looks at a couple of practical examples of that. The more theoretical aspect was published in a review paper a month or two ago. So that's out already. So what it did for that is looked at sort of different scenarios. So different sweat sodium concentrations, different sweat rates, different body weights, different starting blood sodium concentrations, trying to look at what are the things that are important to try and predict, you know, whether you need to consume sodium during exercise or not. Depends on how you phrase, how much sodium you need.
Alan McCubbin 17:33
So in this case, I did it in terms of, you know, what's the percentage of my sweat sodium loss that needs to be replaced? So do I replace 20%, 30%, 60%, whatever it is, and when you do it in percentage terms, you get this really clear model that forms, and you find that a lot of these variables actually don't matter. So the starting body weight doesn't matter. The sweat rate doesn't matter. The duration doesn't matter. The starting sodium concentration doesn't matter. The only things that matter are what is the percentage of your sweat fluid loss that you're replacing? So you know you're drinking 60% of your sweat losses, 70% 80%, and basically, the more you drink, the more sodium you need, and it only really kicks in as an important factor, the sodium, once you get above 80%.
Then the other thing is a sweat sodium concentration. So they're really the only two things that that matter. And I guess when you think about it when you go back to the equation. They're really the only two things. It's the change in total body water and the change in electrolytes so you know, it kind of makes sense that they're the only two variables that will affect things, but you know, when you graph it out, it really becomes clear.
Taryn Richardson 18:35
Okay, I've got some reading to do.
Alan McCubbin 18:36
Yeah, it was a really cool exercise actually. A good thing to do when you can't do any research is to do non-participant based research but yeah, came up with some really interesting answers. And I guess a different way of thinking about it. Some of that was prompted by that study I mentioned before the five-hour study which we're sort of halfway through. Once we started getting results in from that one you know, we were giving people sodium in capsules, and we were sweat testing them first. Working out what their sodium loss was, bringing them back and then running them for five hours in the heat and then giving them capsules to replace exactly the sodium loss that we were predicted from their sweat test prior, and we were replacing 100% of that sodium loss in that study.
Alan McCubbin 19:18
Again, there's no guidelines currently so do you replace 50%, do you replace 100%? We went with 100% because you know a lot of athletes and even some practitioners in the past, that's how they've done it. They've said you know, you lose 1000 milligrams per hour sodium, so you should be taking 1000 milligrams per hour of sodium. So what we realised from that was that, that amount was just simply unnecessary. It wasn't you know, preventing peoples sodium going down if anything it was making their sodium go up more. So that's when we stopped and thought well hang on doing this as like a flat replacement of sodium when you're not drinking to replace every drop of fluid, you know, essentially you over replacing the sodium relative to the water that you're replacing, and it's the balance between the two that's the most important thing. So yeah, that's sort of what prompted me to go back and use these equations to try and model things.
Taryn Richardson 20:05
Yeah, so cool.
Taryn Richardson 20:06
Let me know if this sounds like you. Do you feel exhausted by the end of the training week? Do you crave sweets in the afternoon and feel like you need a nap? Training for three disciplines can be absolutely exhausting if you haven't dialled in your nutrition. It can be frustrating when you can't quite piece together the solid race performance you know you're capable of and confusing when there's so much information out there. But you're not sure what's the right method for you.
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Taryn Richardson 21:10
So what happens if we do over replace sodium? If we overdo how much sodium we're putting into the system?
Alan McCubbin 21:16
So I guess we can think about sodium concentration in the blood. So if we over replace sodium and we go crazy on the capsules or the tablets or whatever, then our blood sodium is going to go up. So our blood sodium concentration will go up when we exercise if we don't drink anything anyway, because no matter how salty our sweat is, it's always less salty than the blood, which basically means that when we sweat, we're losing volume in terms of water, but we're losing some sodium, but we're always losing proportionally more water than we're losing sodium. So your blood sodium concentration, how much sodium compared to water, is always going up. So the only situation where the blood sodium will go down is if you are excessively drinking water. Or if you're exercising for a really prolonged time, you know, 10 hours plus, you've replaced all the water, but none of the sodium and then you might start to get some of that dilution happening to a certain extent. And that's exactly what the model shows as well.
Alan McCubbin 22:12
Yeah, it's really only in those longer durations with that higher fluid turnover where you need to replace that sodium to a significant extent. So having that sodium will do a couple of things, your kidneys will retain more water, but also, you'll have a much greater thirst sensation. So you'll have that drive to drink more fluids. So you know, people intuitively know this, if you have something that's really salty, solid food, you'll get thirsty and you'll want to drink more. The other thing that happens if your osmolality goes really high is that your sweat rate could actually drop a little bit. So while some people might think, Oh, that's a good thing, actually, you're then getting less body cooling going on. And so that affects then your body temperature, and therefore performance.
Alan McCubbin 22:52
If you're having less than 80% of your fluid losses, the model shows us that it's really not going to have any impact. Your sweat sodium will go up anyway if you're drinking less than 80% of your fluid losses. So yeah, from a sodium perspective, not having sodium means it won't go up quite as much, which is probably not a bad thing in that scenario. What it might do, if you are drinking more aggressively during exercise, say 80-90% of your fluid losses or even more and you're not having sodium, then there's a risk that you might have your blood sodium concentration start to go down. And that's when you'd run into the risk of hyponatremia. But yeah, you really only see that over a really long period of time. So things like Ironman, Ultraman, that kind of thing.
Taryn Richardson 23:31
I've had a few clients actually do marathons or long-distance trail runs and have suffered from hyponatremia and they have no idea what it is until afterwards.
Alan McCubbin 23:40
Absolutely. 15 people I think have died since 1980 of hyponatremia. Since people started looking at this, and those numbers are pretty small, granted how many people you see on the start line of every trail run, Ironman, marathon, etc. But it's pretty preventable. The irony is some of those cases now are people that got hyponatremia before they even started exercising. Yeah, they were just drinking copious amounts of water before exercise thinking that they need to be hydrated. There are a couple of American footballers, for example, where the coaches said you need to be hydrated to not cramp during practice. So they went out and drink gallons and gallons of water and ended up with hyponatremia as a result.
Taryn Richardson 24:17
Crazy. So if we don't replace any sodium, nothing's going to happen, unless you're doing events that are maybe sort of 10 plus hours in duration.
Alan McCubbin 24:26
Pretty much. Yeah. And I mean, there's a couple of ways you can think about this. There's the way that we traditionally think about it, that you know, you've got that whole body store of sodium, and if you lose too much of that, you know, something bad is going to happen. Up to 10 hours of exercise, realistically, you're never going to lose more than about five to maybe 8% of your total sodium source like it just can't happen realistically. So it's very unlikely that you're going to see any problem in that context. 10 hours plus, again, it's more to do with the water turnover than it is the sodium depletion as far as we know. I guess it's more the fact you're replacing or turning over water that you're losing over that period of time, and then you're not replacing the sodium, that's when you might run into trouble. Basically means that, you know, to prevent hyponatremia, you have to basically have a lower blood volume, you can't replace the sodium. So yes, you can get away with not having hyponatremia. But you're going to have to have a smaller and smaller blood volume to be able to achieve that. And so that's not great from a body temperature and a performance perspective over time.
Taryn Richardson 25:23
So what advice would you have for all the Ironman athletes that suck back multiple salt tablets, salt capsules every hour, just because their mates told them that they should? Or they do it because they cramp?
Alan McCubbin 25:34
I guess the first thing would be, do we need sodium in triathlon? I'd suggest anything shorter than Ironman, probably not. It's not to say, you know, get rid of sodium completely, like take it out all of your drinks and your food and that kind of thing. I think it's still fine from a taste perspective and the psychological impact it has, and it might encourage us to drink a little bit more, which in some situations might be appropriate. But I guess in those contexts, we don't have to go out to consume a specific amount of sodium, it's more, I guess, I call it sort of season to taste.
Alan McCubbin 26:03
I guess for Ironman or longer, that's when I would say that there might be a role for targeted sodium replacement for people. So again, it depends on their fluid intake. And also, if they have a higher sweat sodium concentration and how are you going to know that? Well sweat testing really is the only way to find out. So I think there is a role for sweat testing, but I think it's more only in that ultra-endurance space. And then I guess you get that sweat test result. And yeah, what do you do with that? So you can stick it into this mathematical model that I've been talking about. But the long story short, even if you stick it in that model, the most sodium you need across any of the scenarios that I looked at less than 70% of your losses need replacing, but in the majority of cases, it's more like you know, 20% to maybe 50-55%. So again, it's not replacing every gram of salt you lose, it's probably somewhere between a quarter and a half is all you need to replace.
Taryn Richardson 26:53
Yeah, wow, much less than what athletes are doing in practice.
So you'd recommend things like salt tablets, or capsules for endurance stuff, sort of 10 plus hours. I'm also thinking some crazy trail runners, you know, I've just had a client do 160km trail run.
Alan McCubbin 27:09
It doesn't necessarily have to be capsules or tablets like it can still be food and drinks and gels and that kind of thing. But sometimes those things might be easier in terms of having more of that control of how much you're getting. But I guess in that context, though, you have to know what's in your capsules and how many you need to take. So you're not just popping them for the sake of popping them because you think you need them you going in there with a specific plan of, I need 600mg/hr or whatever it is, and then that works out to be you know, one capsule every 45 minutes or one capsule an hour or you know, whatever it works out to be. So there's plenty of times that I've used them for ultra-endurance athletes, but it's been more planned rather than just popping capsules for the sake of it.
Taryn Richardson 27:48
Is there any difference between the absorption of a tablet versus a capsule?
Alan McCubbin 27:52
It's a funny story, actually. So during my PhD, we used capsules, I mentioned the high versus low sodium diet. So what we did was gave them all their food and we made it really low in sodium and then we gave them salt capsules to have a really high sodium diet on top of the food or placebo capsule. So they were getting no extra sodium and that kept the overall sodium in the diet really low. And so I started experimenting around with the same capsules and I knew from a colleague of mine I used to work with at a hospital that she'd done some research in a clinical setting using sodium capsules and she said, just be careful because a lot of people get quite nauseated from the salt capsules.
Alan McCubbin 28:26
So I thought, well, you know, how many am I going to need for this study to have in a single meal. I thought four capsules about the most, so I had some leftover capsules from another study took four of those and yeah, within 10 minutes I was in the bathroom, vomiting it up. So yeah, if you dump a big load of salt into your stomach, in a short space of time, you'll get either very nauseated or be actually vomiting.
Alan McCubbin 28:48
So I learnt very, very quickly that you need to slow down the release of sodium. From food, it's fine because it's sort of padded out with all the other bits and pieces in the food and it's not that concentrated, so it's not just dumping as much in your stomach. But yeah, with the gelatine capsules, as soon as they touched liquid, they just completely dissolve and release the contents. But a lot of the commercial salt capsules on the market don't use gelatine, they use cellulose casing, and that does break down more slowly and therefore releases the sodium a bit more slowly. That's generally better tolerated.
Alan McCubbin 29:19
So for my participants where we had to have quite a few in one hit, they would do that. But they would take it with meals, tried to dilute it into the food and fluids they were having as well as the cellulose. But during exercise, you're generally not going to take four in one hit. So generally it's not as much of an issue, but the tablets that don't have any coating might increase the risk a little bit more compared to the capsules. For that reason, that quick dump of salt.
Taryn Richardson 29:41
I love how most researchers test things out on themselves first before giving it to participants.
Alan McCubbin 29:46
I remember reading a study that was around the interactions between sweat glands and the kidneys. So this was 1957. There's only one author in the study. It turns out that the author basically studied themselves 48 times, so they were 48 results, but it was all the one person. So I'm pretty sure it was the author themselves that did that.
Taryn Richardson 30:05
Oh no. Okay, so it doesn't necessarily matter what form we do replace sodium in, as long as it's controlled, and is not necessarily warranted for shorter events.
Alan McCubbin 30:17
Yeah, the other thing I'd say about the form of sodium, and this is the big unknown really, is when we lose sodium from the body, whether it's from our kidneys, in urine, or through our sweat glands, as sweat, the chloride and the sodium always pair up. They always leave the body together. So if you have a low sweat sodium, you'll always have a low sweat chloride and vice versa. So if you're taking salt during exercise, sodium chloride, you're kind of replacing it as it's lost, so to speak. But a lot of the sports nutrition products on the market now are using sodium citrate rather than sodium chloride, mainly because it tastes better.
Alan McCubbin 30:50
But the million-dollar question here, which no one's really answered is, okay, so you're going for 10 or 15 or 20 hours of exercise, you've lost a whole bunch of sodium and you've lost a whole bunch of chloride. So you've replaced all of the sodium but none of the chloride, what does that do? The answer is we don't really know, it's never been studied. What I would say is, it's probably nothing too bad, because we don't have this, you know, epidemic of problems that have occurred, since a lot of companies started making their products with sodium citrate, rather than sodium chloride.
Taryn Richardson 31:21
Do you know how long ago they made that switch?
Alan McCubbin 31:23
Probably the last 10 years, you've started to see more products using sodium citrate rather than sodium chloride. I mean, I guess a lot of the traditional brands of sports drink still use salt, sodium chloride, but a lot of the newer ones that are often marketed at niche areas like ultra-distance events, triathlons, those kinds of things, they're the ones where more often you're starting to see the use of sodium citrate in them instead.
Taryn Richardson 31:45
So check your label people.
So we've mentioned sweat testing a couple of times, is there a benefit to doing sweat testing and how do you go about doing it properly?
Alan McCubbin 31:55
So I think my conclusion from this, and this is one of the main reasons I did the PhD was to look at the whole role of sweat testing in all this and also, you know, sodium guidelines for during exercise. But I think from that, and from the mathematical modelling, I've done since my opinion on the sweat testing is that anything less than Ironman distance for triathlon is probably unnecessary cause you're unlikely to replace fluid to the extent where a significant amount of sodium is going to be necessarily that helpful for you. For me, it's really those longer events where you have to replace closer to 100% of your sweat fluid losses because the deficits going to accumulate over time. So you're going to get closer to that 80% fluid replacement and your thirst is going to dictate that to a degree. So that's where I see the value potentially in sweat testing.
Alan McCubbin 32:42
In terms of the method aspect of sweat testing. Yeah, it's really important one because there's some, you know, pretty dodgy sweat testing practices out there unfortunately. The key thing to realize is sweat sodium losses during exercise vary quite a bit. The second thing to realize is that the sweat, sodium loss at one site of the body doesn't necessarily reflect what's going over the whole body. So in the perfect world, what you'd do to capture sweat is to capture sweat from the whole body at the same time. There is a technique in research for that, which basically amounts to exercising in a giant plastic bag, and all the sweat falls to the bottom or sticks to your skin and when you finish, they basically douse you in a whole bunch of either deionized, water or a chemical of some sort to wash all the sweat off. The bike is still sitting inside the plastic bag. So you've got the bike doused in chemicals, you've got this lovely soup of sweat and chemicals and dirty clothes at the bottom of the bag. And then they basically swish it all around, mix it up, and then take a sample of this lovely soup at the bottom of the bag and then analyse that and obviously have to account for the volume of the chemical that has been added.
Alan McCubbin 33:48
So there's a whole bunch of problems as you can imagine with this for a practical perspective, but also in a plastic bag, you can't replicate the normal airflow you get outdoors, so the sweat rates completely unrealistic. And therefore the sweat sodium concentration is unrealistic as well. So it's only really a useful technique to compare mechanistically that versus what you could do outside. So what we normally do is stick on absorbent patch on a site of the body or more, and then collect the sweat, wring it out in one way or another and then analyse the sweat that comes out of it. But taking sweat from one side of the body doesn't necessarily represent what's happening over the whole body. So there's some standard sites that are used across the body, the forearm, the forehead, the upper chest, or maybe the shoulder blade area, the ones that are commonly used, but they will all have a higher sweat sodium concentration than the whole body.
Alan McCubbin 34:37
The one that probably gives the closest result of the commonly used ones is the one that's halfway up your thigh, but even that's not perfect. So what we do is plug those numbers into an equation that's been devised from that research to compare the whole body via that plastic bag to the patches and then you can plug in the values we get from the patches to estimate the whole-body amount. So a lot of people just think that you just stick a patch on an arm and get a result back from that and then that's your result. But yeah, if it's 40 millimoles per litre at your arm, the whole-body value is significantly less than that. So you need to make sure when you get your result back, is the result calculated for the whole body, or is it just calculated for that particular site?
Taryn Richardson 35:16
Yeah, perfect. Thank you for clarifying that. I've seen a number of reports come from athletes that have had a test and have asked me to decipher it. I think one of the challenges with sweat testing is you get a number, just like doing a body composition scan, like a BIA scan, you get data, but it's what you actually do with that data that's the most important step. That's often missing with a lot of sweat tests, and, you know, stick a patch on, post it out and do it yourself at home. What do you then do with that information, so that we are replacing what we need or don't need and doing that with your hydration as well?
Alan McCubbin 35:52
Completely, you know, just because you get a number, don't hold on too closely to that number, because we suspect it probably varies at least 15%, day to day. So you do that test three times in three weeks, you'll probably get three different numbers that are up to 15% different from each other, even under identical conditions. So don't hold on to that number too tightly. The second thing is that on any given day, you go out and do three different marathons, you'll have three different sweat rates, and therefore, even if the test was consistent every time, in the real world, you're going to get three different results. So I guess the point there is that the sweat test gives you a ballpark figure, but it's not a perfect number that you have to hit exactly, you know, it's only giving you that ballpark.
Alan McCubbin 36:34
I think that mathematical modelling as I was saying before, the biggest driver of the need to replace sodium is how aggressively you replace your fluid losses. Yes, the sweat, sodium concentration does come into that so it's useful information. So it's good to know if you're at the higher or the lower end. But you don't need to know whether it's 45 versus 48 millimoles per litre, it's really just about saying am I at the higher end or the lower end or somewhere in the middle. For me, I think that's the value in sweat testing, just to work that out. Then you're putting that together with your fluid replacement strategy, which really should come first, because that's the part that affects hydration and impacts on performance and then the sodium really comes along and complements the fluid replacement rather than the other way around.
Taryn Richardson 37:15
One of the biggest reasons I love doing sweat testing with people is to do the hydration component because they often turn up already dehydrated and have no concept of what type of sweater they are. Often the ones that are having issues are the ones that are really heavy sweaters, they're sweating, like upwards of three plus litres an hour and they've come because they want to know exactly how much sodium to have. But really the intervention is you need to drink a whole heap more, because you're already dehydrated before you even got here.
Alan McCubbin 37:44
Yeah, absolutely. I've seen some examples where they've had a whole bunch of different issues, and they couldn't figure out what it was and, in the end, it turned out that they did have a very high sweat sodium concentration, far higher than normal. They were replacing the fluid but not the sodium and as a result of that, they were just peeing it out, like that fluid was just a siphon it was going in one ended out the other. It wasn't really benefiting them, and they weren't able to hold on to that fluid. So adding sodium was helpful for them. But for a lot of people, that's not so much the issue. So it's obviously horses for courses.
Alan McCubbin 38:13
But one thing I've started doing over the years, when I look at sweat testing in terms of the sweat rate is not only what is that number, and again, that can vary day to day by at least 10% and more depending on weather and pacing, and so on. But look at what they're actually drinking. So you know, what's the fluid behaviour that's sitting alongside that sweat rate, because that tells you I guess what the problem potentially is. So you know, some people might have a really high sweat rate and they're trying their hardest to drink that amount, but they just can't do it because their gut tolerance won't allowance. So in that case, they need to go out and put some strategies in place to improve their gut tolerance.
Alan McCubbin 38:49
For other people, they're just not getting an adequate thirst sensation, it's just not driving them to where they need to go. So they might need to drink a little bit ahead of thirst. Whereas for other people, they're just not organized to carry enough fluid. So they just don't have access to the fluid when they need it. They need to change their strategy in terms of the logistical side of things. So I think having that information about, you know, what's your sensation of thirst, what’s your gut tolerance, and how much did you drink versus how much you lost, by adding those things into the mix, I think adds a lot to your assessment and really adds value in terms of not just what is the sweat rate, but what's the narrative here and what can we learn from that?
Taryn Richardson 39:26
Perfect. So drinking to thirst. We haven't talked about that much, but it is the sexy term of the era. What sort of distances of triathlon do you think that's useful as a strategy versus what is that's a terrible idea?
Alan McCubbin 39:41
It's very controversial area. I'll start with that. I would start by saying it's gone around in circles. I think we're I've come to with this. In the real world, thirst is a reasonable guide of what to drink or the need to drink more. That's certainly true in most cases, but again, you don't want to take that for granted and that's where testing and including measurement of thirst perception is useful for that. It's one thing to say I'm just going to drink to thirst. But you know what happens if you get halfway through the bike leg, 20kms from the next aid station, you're really thirsty and you don't have any fluid available? Well drink to thirst isn't going to help you, is it?
Alan McCubbin 40:15
So you still need to have some idea of how much fluid is that actually going to be? How much fluid do I need access to be able to satisfy my thirst? That's where I think there's still value. A lot of people just go oh, you know, just drink to thirst like that. Sweat testing is all just a lot of garbage. It's just a conspiracy to sell more Gatorade. But I think at the end of the day, if you don't know roughly what your sweat rate is going to be, then you don't even know how much fluid to carry with you, regardless of whether you're thirsty or not.
Alan McCubbin 40:40
I think in the longer distance events, if we're eight hours into an Ironman, something like that, and we're going well, I don't know where my fluid balance is, whether I've drunk enough or not. I'm not going to pull out the scales and stop at the side of the road and go measure it and see what our full balance has done.
It’s useless anyway because you’ve lost all of your glycogen
So really, the only indication I've got of whether I've drunk enough or not is thirst like it's the only dipstick we can use on the fly in real-time during a race to say where we're at. So ignoring thirst completely is fraught with danger. But at the same time, just going into a race saying I'm just going to drink to thirst with nothing else around that is fraught with danger as well.
Taryn Richardson 41:19
Okay, perfect. So we should be doing sweat testing, but we need to make sure that we are getting it done from a qualified practitioner that can do a test accurately and can use those regression equations to actually measure a whole-body sodium rather than just one site. But then somebody that has the experience to then apply that number in that environmental condition or level of fitness or whatever it is that you're doing, there's a benefit to doing it that way, if we kind of control all of those measures, heading in and heading out of a sweat test?
Alan McCubbin 41:50
Yeah, certainly that modelling shows that the majority of people need very little, if any sodium during exercise, even in Ironman, most people need virtually none. But I guess the problem is, you don't know which camp you're in. Like, you might have a sense of that in terms of sweat sodium, but you're never going to know fully until you test so some people might get disappointed and say, well, the test said I don't need any sodium but until you test, you're not going to know necessarily.
Taryn Richardson 42:14
Now we haven't talked about cramping, and I don't want to open that can of worms too much. But do you have any brief thoughts on sodium replacement for preventing cramping?
Alan McCubbin 42:25
I think athletes have that mindset of sodium is this fixed store in the body and you know, when it drops to a certain level cramping is going to happen. But there's really no scientific evidence that that is the case. People have tried to say, well, you know, is it lack of water, is it too much water? Or is it lack of sodium? What we can probably say from the literature is firstly, cramping is probably a syndrome and what I mean by that is there's probably multiple things that can happen during exercise that result in cramping. So cramping is potentially an outcome of multiple problems that arrive at the same sort of outcomes.
Alan McCubbin 42:58
So we know there's a whole bunch of other risk factors, things like pre-existing medical conditions, certain prescription medications can increase your risk of cramping. We know people that push themselves harder in a race than in training or you know, go out and do a 10-hour race, but have never trained more than five hours. They've all got an increased risk of cramping as well. So there's a fatigue element to it as well. There's a couple of studies that are quite interesting that have looked at Ironman in Busselton, where someone had cramped, but also developed hyponatremia.
Alan McCubbin 43:26
So these guys wrote up that case study and tried to go back into the lab and figure out what was going on. What they showed was that the risk of cramping was probably related to becoming dehydrated first. So when I say dehydrated, loss of fluid, so blood sodium concentration has gone up, and then they suddenly drank a whole lot of pure water very quickly. And if they did that, compared to drinking water with quite a bit of sodium in it, the pure water tended to increase their cramping risk. So for me, this is not a lack of salt per se, or lack of sodium, it's probably the sudden dilution of the blood with the water and so what happens if you suddenly dilute the blood like that what you're going to see is a shift of water into the cells. So it might be this rapid movement of water into the cells that is increasing the risk of cramping rather than lack of salt or sodium per se.
Alan McCubbin 44:16
If you go back to you know, the 1920s and 30s, when some of the first sort of descriptions of hyponatremia and cramping happened in miners, a lot of the cramping was happening in miners that drank huge amounts of water without any sodium in it. So again, it was probably the dilution of sodium from the water rather than a lack of sodium intake causing the problem. So you often see that cramping as well in people that do get hyponatremia in a race or after a race when people stop and then they suddenly chug down a whole bunch of water. But ultimately, cramping is really hard to study. You know, you can't just bring people into the lab and say, Okay, we're going to count to five, I'll just get you to cramp for me and then I'll do some measurements. It's unpredictable, so it's hard to study. So, unfortunately, we still don't know that much about it.
Taryn Richardson 44:57
And multifactorial, like you said. Is there anything that we haven't talked about sodium that you wanted to cover?
Alan McCubbin 45:05
Probably the only thing that we haven't covered, would be sort of sodium over days, weeks, or months of training, as opposed to, you know, just a one-off day of a race. What we see from the sodium study that I mentioned in my PhD, and you see it in countless other studies as well is that your sweat glands will adapt to some extent, but your kidneys adapt within hours of changing sort of your day-to-day sodium intake. If you go really low sodium, you just pee out a lot less sodium.
Alan McCubbin 45:32
So really, your kidneys and sweat glands are going to outsmart you. So there's probably no point deliberately upping the sodium just because you're doing exercise, because your kidneys are going to take care of that, and to some extent, the sweat glands. You can shift that balance out of whack in a single dose of exercise. But over 2,3,4,5 days of training, your kidneys and your sweat glands are going to adapt to their day-to-day level of sodium intake and the deficit you've had. So at this stage, I don't think there's any real scientific evidence that we need to deliberately increase the sodium we eat on a day to day basis.
Taryn Richardson 46:05
So if somebody is a heavy sweater, would it be beneficial for them to start to lower their day-to-day sodium intake to lower their sweat sodium concentration?
Alan McCubbin 46:15
Possibly. As I said, the drivers of sweat sodium concentration are the fluid intake and the sweat sodium concentration, so they're going to vary depending on the weather and the intensity and that kind of thing. So if you're going to do a test, should you go on a low sodium diet to reduce it? Maybe? It's hard to say, I mean, no one's really done that over long term as a deliberate strategy, as far as I'm aware, and then sort of tested again, you know, followed that up to see what impact it has had. Theoretically, it should have some effect, but how much, how prolonged the effect is, how useful it is I guess we just don't know.
Taryn Richardson 46:50
There are a few good topic ideas if anyone listening wants to do their PhD in sodium.
Alan McCubbin 46:54
Yeah, I've probably got another five PhDs lined up if anyone wants to do one.
Taryn Richardson 46:58
We'll put the call out for you. I've got one final question for you, Alan. If you could go for a long ride with anyone dead or alive, doesn't matter, who would it be?
Alan McCubbin 47:07
Oh, that's a good question. I haven't thought of that. Nathan Vanderpol, maybe Tadej Pogačar. I just missed out on working with him actually. By about six months. The team I used to work for they folded and then all the sponsors and some of the riders merged across to another team based in Slovenia, and Toadej was an under 23 riding there at the time, but my PhD was going, I had two kids at that stage, and I wasn't going to come across and work with them. But had I'd done that I would have been a sports dietitian as an under 23. So yeah, maybe him.
Taryn Richardson 47:46
Yeah, cool. You want to ride with like, really epic cyclists.
Alright, awesome. Thank you so much, Alan, sodium master. See, you've definitely earnt that term. I think you should claim it. You can call yourself that at our sports dietitian conference in a few days.
Alan McCubbin 47:59
I'll have to change the title of my email signature.
Taryn Richardson 48:01
Yeah, Alan McCubbin, sodium master. If people want to find you, how do they find you?
Alan McCubbin 48:05
So yeah, a couple of different ways. So I do a little bit of private consulting not very much these days, two kids and an academic job and a podcast makes it pretty time poor. Next Level Nutrition is the business, so if people want to contact me that way they can or through Monash Uni. So you just Google my name and Monash Uni, you should find my email address. The other one will be Twitter. Nextlvlnut is the Twitter handle.
Taryn Richardson 48:33
I'll put that link in the show notes for you so people can click on it and go check you out. Thank you so much Alan, and I'll see you in a couple of days at the conference.
Thanks for joining me for this episode of the Triathlon Nutrition Academy podcast. I would love to hear from you. If you have any questions or want to share with me what you've learned. Email me at [email protected] You could also spread the word by leaving me a review and taking a screenshot of you listening to the show. Don't forget to tag me on social media at @dietitian.approved so I can give you a shout out too. If you want to learn more about what we do, head to dietitianapproved.com. And if you want to learn more about the Triathlon Nutrition Academy program, head to www.dietitianapproved.com/academy. Thanks for joining me and I look forward to helping you smash it in the fourth leg - nutrition!