Oct. 1, 2022

"Sport Supplements and the Athlete's Gut" with Dr Patrick Wilson PhD

Episode 176 of the Institute of Performance Nutrition's "We Do Science" podcast! In this episode, I (Laurent Bannock) discuss "Sport Supplements and the Athlete's Gut" with Dr Patrick Wilson RD PhD (Old Dominion University, Norfolk, USA).

Discussion Topics Include:

  • Why a well-functioning gut is a key, albeit sometimes overlooked, contributor to athlete performance and health
  • Supplements purported to enhance gut function with exercise (probiotics, glutamine, bovine colostrum, other potential GI barrier enhancers, ginger)
  • Supplements that cause gut symptoms (carbohydrate, caffeine, sodium bicarbonate, exogenous ketones)
  • The evidence and effectiveness of supplements vs marketing and hype

Podcast Episode Transcript: Download PDF Copy

Key Paper(s) Discussed / Referred to:

Related Podcast Episodes:

Check out our other podcasts, publications, events, and professional education programs for current and aspiring sports nutritionists at www.TheIOPN.com and follow our social media outputs via @TheIOPN






[00:00:00] LB: Welcome back to the Institute of Performance Nutrition’s We Do Science podcast. This is episode 176. I am Laurent Bannock. And my guest today was Dr. Patrick Wilson, who some of you will know because he's been on the podcast before, where we talked about the athlete's gut. He's a well-known expert in this area. Has written a book on this topic, which we did happen to discuss again today, which I highly recommend. But also, lots of peer-reviewed scientific articles around this topic. 


But specifically, today, we had a conversation based off a new review that he's published on sports supplements and the athlete’s gut. And as it was, in our last conversation, today ended up being a really interesting conversation around this concept of the athlete's gut and the various problems that can occur as a result two different kinds of exercise and performance related activities on gut function itself. And also, the consequence of taking certain types of supplements, like certain ergogenic aids, like sodium bicarbonate, for example, are known to cause gastric distress or gut issues in some people. And there are a number of supplements potentially, that could help with that. 


And of course, in the wider commercial environment, there are all sorts of products out there promoted to support gut function in general population, of course, but also now in athletes, things like probiotics, glutamine, bovine colostrum, and various other substances. However, the evidence may not match the enthusiasm that the commercial noises will promote. So, we get into that, and we talk about the evidence and unpack the evidence into a variety of applied context. But we generally discuss why you should or should not be using these supplements or recommending them to your clients or your patients. And for researchers, maybe where we could develop some really useful research to impact this topic to help inform our decision making as sports nutrition practitioners. 


So anyway, before you get to listen in on that really interesting conversation I had earlier, do go to our website, www.theiopn.com, where you can find all our podcasts, the back catalogue, and access links to papers, that sort of thing, that we discuss. Whilst you there, please check out our brand-new Advanced Professional Diploma in Performance Nutrition. Every few years, we rewrite our program and upgrade it to the next level based on our experiences of delivering this program over the years, but also to our evolving understanding of the needs of effective, successful, highly impactful practitioners working in private practice, working in group coaching sessions. And of course, in elite or professional team settings. These are the interests that we are addressing in our Advanced Professional Diploma in Sports Nutrition Program. So, you can check that out. It's all new. So, go check that out. And whilst you there, also have a look at SENpro, our software platform that, again, is something that adapts and evolves based on everything that we do and the feedback that we get. And also, our own uses working with private clients and elite athletes, including myself, of course. I'm a big fan of SENPro. And I don't mean that just to be biased. I really do find it an integral part of my practice to support my clients to help work with their habit and behavior coaching that I do with them. And in the teams working with large groups of athletes is all where I find SENpro particularly useful. As I'm sure you will. But anyway, go check it out, www.theiopn.com


And now, here's my conversation with Dr. Patrick Wilson about sports supplements and the athlete’s gut. Enjoy. 




[00:04:08] LB: Hi, and welcome to the Institute of Performance Nutrition’s We Do Science Podcast. I am Laurent Bannock. And today, I'm very pleased to welcome back Dr. Patrick Wilson. Patrick, how are you sir?


[00:04:20] PW: I'm doing well. Thanks again for having me back on the show. It's the first conversation we had must have been a year or two ago, I think.


[00:04:27] LB: Yeah, you know, it's all a blur. 


[00:04:29] PW: Yeah. Yeah. 


[00:04:30] LB: It's all been a blur. It's all been a blur.


[00:04:31] PW: The fun that you get in your life, everything becomes more and more of a blur. So, it's sometimes hard to pinpoint exactly when things happen. But yeah, it's great to be back on the show.


[00:04:40] LB: Yeah. Well, the reason why I wanted you back is that I read one of your new reviews on sports supplements and the athlete’s gut in frontiers. I'll add a link to that in the show notes. Of course, when we last spoke, we talked about the athlete's gut, which, amongst other things, you've published a book on. But also, lots of publications. And you're well-known as an expert in this field, both as an academic, as a practitioner, which we'll come back into in a second. 


Now, look, I've had these podcasts with yourself and others on topics that relate to the gut supplements, probiotics, that sort of thing, the microbiome. It's such a massive topic, and it's expanding rapidly. And I would definitely say it's an area that continues to grow both in terms of sort of interest and, dare I say, sex appeal, if one could even use that phrase, in sports nutrition. It is just a really great, great topic. And no pun intended, but I've got a gut feeling. See what I did there? That we're going to have a really interesting chat today. But this time, more about supplements, rather than just about the gut. But we'll link it all as we go. 


But Patrick, just in case people haven't listened to our previous podcast, which you must listen to, folks. You'll make more sense out of this chat today having listened to that podcast. But tell us about who you are and your journey to where you've been now as an academic and as a practitioner.


[00:06:11] PW: Yeah. So, I'm at the Old Dominion University in Norfolk, Virginia. I've got a background in nutrition dietetics, and then exercise physiology, sports nutrition. I grew up in the state of Minnesota. Went to school in a few different places there for my undergraduate and graduate studies. Ended up at the University of Minnesota to do my PhD there, and kind of focused on sports nutrition related topics. But more specifically, it was on the issue of multiple transportable carbohydrates. So, that's kind of what I did my dissertation work on. 


And then just fast-forward roughly seven to 10 years later, I’m now, again, at Old Dominion University. And for the last several years, I've spent a good amount of my research time looking at issues related to gut function with exercise and sport and athletes. Decided to write a book a few years ago, The Athlete’s Gut, which came out, I think, in spring of 2020. 


I really wanted to kind of write a very evidence-based, science-based book, but also that was relatively accessible to people. You have to have, I think, some bit of science background to really get the most out of it. But I tried to make it as digestible, if you want to use another pun, as possible. And also, comprehensive. Just there's a lot of books out there that talk about the gut in a chapter or in a couple of chapters, but not really focused on it as the sole topic. And I feel like there's enough information from nutrition, to psychology, to supplements, to the environmental conditions, to personal factors that influence whether or not someone has gut dysfunction or gut problems during exercise. So, that was kind of the impetus for writing the book. 


And this paper actually was one of my former professors at the University of Minnesota reached out to me and asked me to do an invited review. Obviously, still underwent peer review and everything. But that was kind of actually the reason that I ended up writing this particular paper on supplements, specifically, since that is an area where there's a lot of marketing for supplements to help gut function. 


And then beyond those supplements, there's a bunch of other supplements that people take that might impact the gut in terms of side effects. So, that's kind of the overarching kind of organization of the paper, is that the first part is supplements that people take or marketed as gut enhancers. And then the other part of the paper is things like carbohydrate, caffeine, sodium bicarbonate, things that are performance enhancers that have gut side effects. And what do you do to manage those gut side effects? So yeah, that's kind of where the paper is coming from and the origins of it.


[00:08:57] LB: No. That's great. And listen, there's all sorts of things I've sort of penned that I want to get into. And hopefully we'll have time to cover some of those areas. But just to sort of knock out a couple of comments that I typically make in almost every podcast, or at least a lot of them, it seems, is things like we talk about athletes. We talk about sports. And of course, there's many different variations there. But a common denominator there, of course, is the human being that's involved. And they're not just athletes. They're not just soccer players, or weight lifters, or endurance people. They're regular people for the most part. And they've all got guts in some format or another, which we can explore. 


But again, in sports science, we tend to talk about things in terms of things like calories, and macros, and protein, and stuff like that. And even when we do talk about the gut, we talk about things that cause gastric distress. We talk about the various benefits for example of say probiotics in that regard, which of course, we have talked about, and we'll talk about and some other novel food and/or supplement compounds. 


But at the very beginning of this review paper, you've got a – The very first sentence actually, for me, I think was one of the most important things that we actually need to expand upon just to make it absolutely clear why the gut is so important. And that is that a well-functioning gut, not just a gut, not just a functioning gut, but a well-functioning gut, is key to contributing to athlete performance and health.


And as I said, an athlete is not just there to perform. They have to maintain their health over a protracted period of time in order to get to the best version of themselves. So, why – Just bring us back. With your clinical background as well. I think this is where this is useful. Why do we need to think about the gut beyond just performance, for example? Or why the gut actually is more directly linked to performance than we otherwise might think, particularly when the over-arching theme here is nutrition, of course?


[00:11:04] PW: Yeah. I mean, I think is your maybe pointing to that sometimes papers that are focused on gut issues in athletes, it's kind of isolated to before, during, and after a competition or exercise. And of course, that's important. Like, if you are experiencing major gut symptoms or dysfunction while you're competing, that's a big problem that any number of things might be contributing to, from nutrition, to the environmental conditions, to personal factors. 


But the broader point, you're bringing up that day-to-day health. How an athlete feels? How they're sleeping? How they're eating day-to-day? Those sorts of things play a larger role over-time whether or not they're able to train as much as they want, as hard as they want, have a life outside of sport. And the gut is a big part of our overall bodily function. 


I mean, people just will sometimes think it's the tube that helps you digest food, which is true, of course, but it's an interface with the larger outside world. It's a surface area that interacts with trillions of bacteria, viruses, other microorganisms. And if you've got some issue that is impacting the way you feel subjectively, whether that’d be IBS, or dyspepsia, or some unidentified issue, or if it's actually manifesting as malabsorption. Like, you've got some issue where you're not absorbing nutrients, then of course, it's going to impact things like your immune function. It's going to impact your ability to just handle training and to consume enough food and energy to really match the demands of what you're doing from day to day. 


So overall athlete health, I think, is obviously a very important piece of the puzzle and not just what's happening during competition. I think with, as you mentioned, kind of the good stuff, sometimes a lot of the focus is just on what is happening when they start exercising to the gut or shortly thereafter? And then there's not as much attention maybe on the broader picture outside of the context of training or competition.


[00:13:15] LB: Sure, yeah. And of course, depending on which perspective you've focused on, that one will have an impact on the other, of course. Whether it's the acute or more chronic impact of training, and lifestyle, and supplements, and so on, on the gut. Either which way, we want it to be, as you stated, a well-functioning gut, which is why I just wanted you to help clarify what that term meant. 


Also, because there's a lot of terms that get used in sports science, sports nutrition, and so on. And when we get into the gut, as we do when we talk about immune function, terms and phrases come up that might be less familiar to sports scientists, strength conditioning coaches, that sort of thing. When you say gut, that makes you think of something. But also, you'll then see commonly things like gastrointestinal tract. Broadly, we might refer to the digestive system. Maybe you could centralize this for us. 


[00:14:08] PW: Sure. That's a good point. I mean, I think as writers, we oftentimes will switch the terms just to make it sound interesting. Because if you keep using the same term over and over and over and over again, it gets monotonous. But yeah, usually when I say the guts or gastrointestinal tract, generally, most of the time we're referring to is this tube that runs kind of through you from your mouth to your anus that is very simplistically a kind of a tube. But it's obviously much more complicated than that in terms of the way that it looks changes throughout that whatever it is 25 to 30 feet. Whereas you go from the mouth, to the esophagus, to the stomach, to the intestines, to the large intestine, if you look at the lining of those different parts of the GI tract microscopically, they look different, because they have different functions. 


The easiest example of that is in the intestines where you have all these like finger-like projections and hair-like microvilli that help to increase surface area for the purpose of absorbing more nutrients. And that's a physical feature of the intestines that helps carry out its function. But yeah, the gut is not only the tube, but also the things that are secreted into it. The enzymes that help break down foods that help you absorb those nutrients. And then also, the accessory organs that are involved. You can include the pancreas, the liver, because they're secreting things into the gut. 


You can also kind of think of the nervous system that's embedded in the gut, that is also a part of it. Your intestinal wall is contracting throughout most of the day to keep stuff moving through. And a lot of that is done reflexively based on feedback that those neurons in the intestinal tube itself are sensing. 


So yeah, it's very sophisticated, actually, in terms of all the number of parts and pieces. But generally, that's what we're kind of thinking about is from your mouth to the back end, all the organs that are involved in that process of breaking down and absorbing nutrients. And then also, sensing the environment, right? That's the other piece that people forget about, is that it's a sensory organ. It is kind of trying to keep track of what's going on in that external environment from the composition of bacteria, to the nutrients that are going through. It needs to be aware of what's in there, so that it can defend itself and also absorb the things that it needs to absorb. 


So, it's a very sophisticated system that I think I've said this many times, is that it gets underappreciated until something goes wrong. And then you're very aware that there's a problem with the GI tract. It becomes very apparent when you've got a major issue.


[00:16:56] LB: Yeah, and we'll discuss this further and a bit later. But it's not something that under the radar just functions like many parts of the body. Generally speaking, they're just not aware of them doing anything. As that phrase, a gut feeling, we can become acutely aware of what's going on in our guts. And the body has numerous attractive ways of displaying symptoms that can indicate that there might be some problems in the gut area. Of course, some of which might be due to illness, infections, that sort of thing. But also, it might be due to some of the challenges that are placed upon it by the various things that acute and prolonged exercise can do to the gut, and/or the timing of the ingestion of foods. And I'm thinking even something like just a pre-match meal that's consumed at the wrong time proximal to a kickoff all the wrong constituents in that meal that take considerably longer to digest, fats, and certain kinds of carbohydrate, and so on. So, there's quite a lot there. And I know that the review is particularly focused on the impacts of vigorous and prolonged exercise, which we're going to get into. But I didn't want to pass by the overall complexity of the gut, and also the influence and the overall impact, our day-to-day choices of food, and exercise, and so on, can have on it, which of course, we talked about in a previous podcast in great detail. 


So, if we fast forward them to this situation where, over and above just regular people walking around and their guts are doing what they do, and yes, they might have issues here and there. But specifically, as just referenced, is athletes or exercises in general do put themselves into a situation that may bring about a number of issues, which sedentary people, let's say, are unlikely to experience, which I'd love to have you take us through in terms of sort of types of exercise. And maybe even I'm thinking triathlete jumping into an open water swim and accidentally swallowing water from the lake. That's another interesting byproduct of their exercise. But what sort of issues is the athlete’s gut likely to be exposed to as a result of exercise?


[00:19:21] PW: Yeah, as you kind of alluded to, it depends on the nature of the exercise, for sure. So, we think about duration, intensity, and environmental conditions is probably being the primary factors. Modality of exercise probably also plays a bit of a role. Those would be kind of the four key things that I would look at in terms of what's the likelihood of GI issues and what's the magnitude of those issues. So, the longer the exercise, the higher the rate of symptoms you see, usually. 


So ultra-marathons, for example, are kind of notorious for having lots of nausea and vomiting. I mean, you might see upwards of 50% of competitors in those races saying they've got some level of nausea, substantial proportion that have pretty severe nausea that it impacts their performance. So, duration is a big one for sure. 


Intensity certainly can be another. So, even something that's super short, done at a high intensity, can also increase the likelihood of certain issues. Now, the types of issues might be different. Again, nausea is one that will come up with really high intensity exercise. Done repeatedly, it can be problematic, especially like if you do it on an empty stomach. People sometimes will hear that fasted training is good for them, which may be the case in some scenarios, but they decide to get up in the morning, not really eat much, they drink caffeine from coffee or some other source, and then they do an interval workout, and they're ready to throw up. And they don't really know why. They're kind of combining a bunch of different things that stimulate stress response, and that can trigger nausea, for example. 


So, intensities are another one. So, beyond that would be environmental conditions. Definitely, studies would suggest that the hotter it gets, the more difficult your body's going to have distributing that blood flow equally to places that need it. So, you think you're working in a hot environment, and beyond the blood demand of the muscles just to work, you also have to supply enough to the skin in the periphery to cool yourself off. And that's going to deprioritize the gastrointestinal tract in terms of blood flow. 


So, lack of blood flow to the gastrointestinal tract will manifest as symptoms. But physiologically, you might see some kind of weakening of these tight junctions that hold some of those intestinal cells together. You get some gut leakiness. So, that's been shown in a number of studies that stressful exercise under hot conditions can make GI symptoms worse. 


And then modality, that one's a little bit trickier to study. There's been, I think, a couple of studies that have tried to more directly look at whether or not running, for example, causes more issues. Most of the data is just kind of observational and saying that runners tend to experience more issues than cyclists. But it might be that there's just certain types of GI symptoms that runners experience more of. 


Lower symptoms might be more problematic, like diarrhea, cramping, loose stools, the runner's trots, that term has been around forever. Whereas cyclists, maybe in some cases might be experiencing more reflux, regurgitation. Stomach fullness especially if they're trying to eat a lot on the bike. So yeah, it's a bit tough to universally say that running causes more issues than cycling. I don't necessarily think that's the case. I think it depends a bit on the situation. 


So, those would be the main factors, I think, that are going to dictate a lot of the variability you see from sport to sport, or race to race, event to event why there's differences and how common and severe these problems are. Those factors play a big role.


[00:22:57] LB: Yeah. And of course, I guess what makes this interesting is just the individual variation that exists from person to person, sport to sport. And it's like most things in sports nutrition, you're going to have to learn to individualize everything that you do, which is what makes this complicated, of course. Because you mentioned the commercial sort of side of things right at the beginning. That is an issue, particularly when we talk about functional foods and supplements that in some form or another are supposed to support gut function, digestive function, the microbiome. It's a big business. It's a big thing. It's not just sports nutrition. It's nutrition, which is even bigger than the sports nutrition market. It’s just absolutely vast. 


But we'll do our best to have a look at some of these areas. But of course, we're not just talking about the impact that exercise can have on the gut. As I mentioned, there are factors like the consumption of certain foods or meals or supplements that can result in issues as well. And therefore, you're looking to find ways of dealing with those. And you talk about that in the paper, of course. For example, supplements that cause gut symptoms. Maybe you could just give us just an overview on that also.


[00:24:14] PW: Yeah, some of the supplements that I kind of decided to focus on some more of the evidence-based ones that actually have a benefit that I actually use fairly often. Because there's definitely some obscure supplements we could kind of talk about causing GI issues potentially. But I wanted to focus mostly on the ones that are either commonly used or have a good evidence base behind them. So, that would be carbohydrate, caffeine, sodium bicarbonate. 


I also talked a bit about hydrogels, since they're becoming pretty popular in the last few years. Yeah, those are the main ones that I think I focused on the paper. So, carbohydrate obviously is a nutrient that is a focal point. For athletes that are doing extended exercise, anything more than 60 minutes, and you get into that territory where it might be worthwhile to start ingesting something during the exercise. 


But there's tradeoffs, right? I mean, it's difficult to digest and absorb foods while you're working hard especially and for long periods of time. So, it's kind of a delicate balance to figure out how to do that. Well. So, the recommendations that I talked about around carbohydrates revolve around basically the amount and then the form that you're going to ingest. 


So, for example, including a mix of glucose and fructose, if you're going to be ingesting a large amount, or a high rate. And then that there is some limited evidence to suggest that solid forms, like bars and things like that, may in some cases cause more problems if that's the majority of what you're consuming. And that's probably going to be most relevant for like an ultra-athlete. Like, a high-level marathoner isn't going to be queuing bars during a race anyways. So, they're going to be sticking to beverages and gels. So, I don't know that it's super relevant for most of those athletes. 


But for an ultra-runner who might be out there for 15 hours, you've already got some gut compromise. Stuff may not be emptying from your stomach as fast as you want it to. But late in the race, to chew whole foods, and if you just are trying to get it down, you don’t chew it all that well. But at least in theory, that could cause some problems. 


And couple of studies have shown that bars, if ingested at a high rate, might cause more symptoms than liquid formats or gels. So, that's something that kind of keep in mind for an ultrarunner, is if you're going to eat solid foods, or bars, or things that haven't already been kind of processed, you kind of have to probably think about the amounts. And then perhaps how long you chew that food may make a difference. 


That hasn't been directly studied in terms of how much you chew or food versus its impact on digestion and performance. I've got a master's student who's hoping to do study on that. But we'll see what turns out from that. So, carbohydrate, that's basically kind of where I hit on in terms of the things to look at to manage GI issues.


[00:27:09] LB: Yeah. And, look, this is –I mean, this expands into topics that goes well beyond the time that we have available today. And of course, I've had some of these discussions. You mentioned carbohydrate format. I did a podcast not so long ago with Dr. Mark Hearris all about that carbohydrate format supplement thing. And Mark is one of our senior tutors on our team here at the IOPN. Proud to say that. 


But everything that there is about these topics is a – I mean, it's a PhD in itself. It's a paper, a group of papers. And it's certainly been a podcast on most of these topics. What I'm interested, particularly here, though, is something you hinted at before. You focused on just those that has a bit more of the evidence-based. 


Now, the evidence-based bits quite interesting. Because, as we've discussed, there's a lot of products out there, a lot of commercial interest in this that doesn't necessarily have the evidence to support it. But of course, whether people are aware of that or not, and that might be down to lack of training or their ability to critically appraise the products, or indeed the science, because something I want to talk about in a minute is sort of the quality and the quantity of science that's in this area. And most importantly that, which is actually relevant, particularly to athletes, where maybe some of this information is coming from a different community of people as opposed to specifically athletes. Or the types of studies themselves aren't necessarily done in a way that you would consider, which you have mentioned in this paper actually. 


Let's just quickly talk about that. Because, of course, we are talking about what we know, what we don't know, what we think. Since you have spent an enormous amount of time in this particular area, what are your thoughts on that specific topic?


[00:28:55] PW: Yeah, specifically for the supplements that are marketed as gut enhancers, I don't think that the evidence is particularly strong related to practical impacts for athletes. That's the kind of caveat there, is that – or the key point, is that most of the studies that I kind of talked about in this review, focused on physiological markers, like gastrointestinal permeability, evidence of endotoxemia, which these are established markers that should be collected, can be collected, or good scientific outcomes to look at, or done in rigorous ways.


But with that said, there's a debate about how much those markers really translate to more practical, tangible things for an actual athlete. Meaning, like, does it actually reduce gut perceptions or problems? So, nausea, cramping, loose stools. Like, does it actually manifest in a material way for most athletes? 


And then for most of these supplements, it's not clear that they do. So, the only ones that really have shown any reductions in symptoms, for example, would be probiotics. And even that, it's a pretty mixed bag. Like, some studies don't show any improvements. Some studies show modest improvement. And then there's a couple that show maybe a little bit of an increase in certain symptoms. 


There’s no`– by no means, is there a universal improvement in symptoms, even with probiotics. And the other supplements that I've looked at, glutamine, bovine colostrum, and other supplements that are supposed to enhance sort of the gut barrier, there's evidence that they do that. Meaning, you see that, functionally, it seems like the gut is less leaky during or after exercise. But either the studies did not assess any subjective symptoms. Or when they did, there was no clear benefit. 


Now, it doesn't mean that there wouldn't be benefit, let's say, three or four more hours into exercise, because that's possible. Most of these studies are asking people to exercise for 60 minutes or something like that. Because just, realistically, to recruit enough people, to ask them to exercise for three or four hours at a time multiple times is just not possible. But it's rare to be able to achieve that. 


So honestly, I think there's possibility of a benefit for some of these supplements like glutamine and bovine colostrum as got barrier enhancers. It's going to be very difficult to show that conclusively, given the limitations of what we can do with the amount of time that people are willing to devote to a scientific study. So, I don't know if there's ever going to be complete clarity on a lot of these supplements. 


So, that's probably advantageous for supplement makers, and that they can kind of point to some of these studies and say, “Hey, there's a benefit here. It improves gut barrier integrity. But we really don't honestly know all that well what it does more materially for athletes from day to day.” 


I'm somewhat skeptical that like glutamine, for example, really is all that beneficial. Even though it has been shown in a few studies to improve gut barrier integrity. Symptoms either were not improved or not collected. And then another example is the placebos and those studies were just no calories. So, most runners are going to ingest carbohydrate. And we know that carbohydrate reduces gut barrier issues. 


So, glutamine is an example of one, right? There's a lot of interest. And I understand the interests and the studies that have been done have been well done from a number of perspectives. This isn't like a criticism of those particular studies. It's just the context is they can't really tell us what a lot of people think they can tell us.


[00:32:29] LB: Yeah. I mean, that's why I was saying that a lot of people, they don't realize the challenges that there are in actually taking a look at the evidence, and actually still trying to whittle that down to how actually useful is this as it relates to me as a practitioner wanting to consider whatever it is that I can do to help my athlete get the greatest possible result on the day. 


And there are way too many options across the spectrum of not just nutrition, but training modalities. And should you get that extra hour of sleep? And, well, what about the mindset and everything else? I mean, there's just a lot of things. So, I think one needs to understand that most of these things aren't magic bullets. And like you've said, actually, in the scheme of things, it's a bit questionable for reasons you've just pointed out. The thing about scientific studies is it has to reduce things down so that we can try and understand what's going on. But of course, that isn't what happens in the real world necessarily at least. 


And you talk about this in the paper. And there's some useful shots in here where you, for example, figure one here. You list probiotics, glutamine, bovine colostrum and numerous other supplements, and the various things that they may or may not do as it relates to the strength of the evidence that's associated with it. 


And even on reading that, you're left with the idea of, “Hmm, there's not a lot here to convince me that there's an overwhelming argument that I should be spending a lot of time focusing on these things.” But with that said, they are options, Patrick. So, let's maybe go through some of these things. You've just mentioned probiotics. I've done a lot of podcasts on probiotics, personally interesting, because I've helped contribute to various papers on that topic. But for you, what are the main key takeaways from the evidence-based perspective that you think we should be bearing in mind as it relates to probiotics? What are the key factors there?


[00:34:37] PW: Yeah, I think as you hit on the evidence base is challenging to interpret in a lot of these areas. I think that's especially true for probiotics just because of the number of variables you can kind of manipulate from strange species to format of delivery. That makes it, I think, especially difficult to give really evidence-based recommendations for probiotics. 


That being said, if an athlete decides that they want to try probiotics, even if there's mixed evidence, most of the studies that I've seen are kind of either using bifidobacteria, or lactobacillus bacteria, multi strain species products with dosages that range from maybe 1 billion to 100 billion colony forming units. And taking that for at least a couple of weeks. In those cases, you might see some benefits with respect to certain types of GI symptoms. 


I think the caveat is that most of the time, these are not dramatic improvements. It's not going to take somebody who has severe GI symptoms daily and during their training and get rid of that. I think that's a – If we can say one thing about these supplements, is that, as you mentioned, they're not magic bullets. There might be modest improvements for most people. A very small number of people might have more substantial improvements. But I don't think most athletes should expect to resolve their gut problems by taking a probiotic, or really any other supplement. 


But yeah, if you decide you want to try probiotic despite the lack of evidence of the benefit for GI symptoms specifically, that's probably what I would do, is find a product that has a dosage of at least 1 billion colony forming units per day. Maybe a multi strain product. Dose it for at least a couple of weeks and see what happens. Relatively safe for most people. I don't think there's a huge amount of safety concern there. But there's no guarantee that it's going to be all that helpful. So yeah, I don't know. I mean, what's your perspective on it? Because I know you’re an author, a coauthor on that.


[00:36:38] LB: Yeah. I was on the same consensus statement. I mean, I'm looking out my window, not out of rudeness, Patrick, but it's because I have a constant challenge with my lawn, partly because my dog destroys a lot of my lawn. So, what happens is, is I'm constantly throwing grass seed out there. And one realizes that, depending on the time of year, depending on the conditions, whether it's rain, whether there's soil for the grass seeds to actually go into, or is it just going on top of dead grass, all these sorts of things, are a bit like, for me, like taking probiotics. Unless you've got a lot of the right conditions, particularly the right foods traveling through the digestive system. And I'm thinking things like fibrous foods, vegetables, and so on. 


I did a podcast a while ago all about the microbiome and what's described as the fiber gap, and just how important fiber is and other substances that pass through that environment is just like my lawn, basically. It's far more complicated than just banging grass seeds onto it. And I think that's what happens with probiotics, is, as you've already made clear, people take the pills, and they think that's it. Job done. No, not at all. 


And it could be a waste of time. But at least it's a relatively safe waste of time. But as with all things, it's a combination of factors that influences health and performance, isn't it? Rather than just this one specific area? So, I can see that that probably drives you nuts when people talk about probiotics all the time? Because, of course, it's so closely linked to the gut, but not necessarily in the right ways. 


I mean, in terms of flipping it actually, flipping the coin onto the other side of the coin, do you feel that too much attention and focus is given to supplements where other things actually are far more influential, I propose, to the gut and how it functions?


[00:38:43] PW: Yeah, I think that's probably true. I mean, there's other more consistent predictors of GI issues in athletes in the general population, then what supplements are going to be able to do for you in terms of resolving those issues? 


So, examples certainly would be continued psychological issues, anxiety, stress, consistently linked to a higher prevalence or severity of a host of gastrointestinal symptoms. And that's both in nonathletes and athletes. I mean, it's pretty consistent in studies that I've done. And these are observational studies. They're correlative. They're not experimental at this stage. But we generally see that there's a modest correlation between the severity of anxiety that people are experiencing and the severity of symptoms that they say they have during exercise. 


So, getting, if you can – and some of that is obviously personality and life circumstance. And sometimes there's not really a whole lot you might be able to do about it. But there are things you could probably do to reduce the severity of the day-to-day anxiety that you might be experiencing, whether it’d be through medications, cognitive behavior therapy, working with therapists, those types of things. That might translate to fewer, fewer gut symptoms. 


The day-to-day input of what you're eating is going to make a big difference, obviously. And then there's other factors that are going to play a role as well. I mean, sleep actually is one that I've done a couple of studies that have shown correlations between chronic sleep issues and GI dysfunction. And the reason why that might be is I don't know that it necessarily directly impacts the functionality of the gut, but perceptions of pain in discomforts. We take this to the context of other medical conditions, whether it’d be arthritis or something else. Lack of sleep seems to exacerbate people's feelings of pain and discomfort. And that could also be true for gut issues. If you're not sleeping well and not doing that regularly, that could potentially translate to more GI issues. 


So, in most cases, I think it is multifactorial. It's not one thing. It might be that there's one thing. Someone's making an incredibly unwise nutritional choice before exercise or during it, and you’d fix that, and it's all good. But I think in most cases, there's a combination of things that's contributing to somebody who's experiencing moderate to severe gastrointestinal problems. I think that's more common than the reverse, which is it's just one thing that you have to figure out and then you fix it. I don't think that's the norm.


[00:41:21] LB: I think a lot of people will approach this by virtue of supplements being pills, primarily, with the mindset that it's like aspirin, ibuprofen, whatever. I've got a problem. I take the pill. And then the problem goes away. At least the perception of that problem goes away. But of course, that's not how these things work, generally speaking, is it? So, therein lies a bit of an issue. But then of course, you've got the anxiety that sets in if you feel that you haven't tried to do something to solve these problems. And then, particularly very elite athletes, the ones that I've worked with, they are of a mindset that they will be worried if they feel they haven't done everything that they can. And maybe that is a situation that the supplement industry takes advantage of that potentially. We don't know. 


But bring it back then to the other one, which is very common, which is glutamine. Of course, if you look at the ingredients of a lot of supplements that a lot of athletes take, like protein powders, and so on, particularly animal-based products, you're going to find glutamine on there. But why all the rage about glutamine? And why all the concern about the rage about glutamine? What's your perspective on that?


[00:42:37] PW: I mean, there's a lot of history of interest in glutamine as a supplement just for exercise in general in terms of maybe the immune aspects of post-exercise, athletes having issues with getting sick. And that's not uncommon especially during heavy training periods. 


So, glutamine is an amino acid that circulates in high levels in the blood, and it can sometimes decrease after exercise. And there's concern that maybe there's some immune implications for that. For the gut specifically, though, it does seem to be an amino acid that the gut prefers to use as a fuel. So, like tracer studies will have individuals ingest a certain amount of glutamine. And a good chunk of it never actually ends up into systemic circulation or the blood. It's kind of gobbled up by the gut tissue. And a lot of that is probably used for energy by gut cells. 


On that basis, there's some theory that, especially during times of stress, physical stress, that supplying glutamine to the gut might help prevent some of those issues with cell dysfunction that tends to happen. When the blood flow to the gut starts to decline, part of it might be a lack of energy that the gut has available to it to keep the cells working the way that they need to. And supplying glutamine before the exercise may allow an extra source of fuel for those gut cells to kind of rely on and survive on under those stressful conditions. 


I mean, I think there's certainly justifiable reasons to look at glutamine as a gut enhancer with exercise. I think it's problematic in terms of where we're at right now if a company's marketing glutamine is a gut enhancer with exercise, it kind of goes back to what I was mentioning earlier, and that most of the studies to date have kind of looked at these physiological markers, which are very interesting and something you should understand, the physiology of what happens. But the practical implications are still kind of yet to be determined. 


And I guess moving forward, the one other thing I mentioned I'd like to see with studies in glutamine is to actually use a realistic placebo. I guess I wouldn't call it a placebo necessarily, but a comparison intervention that we know already probably helped to enhance that gut barrier integrity. And that's just carbohydrate ingestion. 


If you have someone who exercises fasted and somebody who exercises with carbohydrate ingestion, when they ingest that carbohydrate, it does help to maintain some blood flow to the guts and does help to maintain some of that gut barrier integrity. To me, that's a more fair comparison, is just carbohydrate. And to see, does glutamine outperform that? If glutamine outperforms that, then, yeah, we're on more of a track to say that glutamine is something that possibly would be a supplement that during exercise enhances gut function. But if it doesn't do it better than carbohydrate, which most athletes are going to be consuming anyways, then I don't know that there's a real strong rationale to use it on top of carbohydrate. So yeah, it's got to yet to be determined. 


And again, all the studies that have been done, I understand the reason for using like a noncaloric placebo. It's not really a criticism directly of the studies. It's just It limits what we can say about the practical use of glutamine.


[00:46:02] LB: Yeah, I'm pleased use the word practical, because many reasons why the practicality of a given intervention is a value, of course. And that will also segue into the reasons why somebody needs to supplement. And by that, I mean, by actually understanding what the word supplement actually means. Or at least it should be interpreted. Whereby, for example, you might have a vegan who may not have a source of foods that are rich in glutamine, which may or may not be relevant, as you've just pointed out. But one area, which of course, is a big issue that I find myself having to wrestle with quite a bit is those athletes that go out of their way to avoid carbohydrate in the belief that it's bad for them, particularly will impact their body composition negatively, which is usually madness as it relates to the types of athletes I usually work with. 


Maybe we just quickly talk about that from your perspective and why carbohydrate might also actually be important for the gut, not necessarily just for performance. But what are the implications of that from your perspective in terms of carbohydrates in the gut?


[00:47:13] PW: Yeah, I think what can happen sometimes is an athlete might be restricting food intake. As you mentioned, a lot of times they will restrict carbohydrate, with the idea that that's going to help maybe maintain their weight or help them lose weight. They want to also make sure they're getting enough protein, which is great. That's something that I think should be the focal point, especially if you're trying to lose weight. But carbohydrate a lot of times takes the brunt of that.


And you can kind of tie it into degree to the energy deficit in sport concept in some ways. And that if an athlete is under feeling, a lot of times they're under fueling carbohydrate. And it can be counterproductive to gut health and function. When you don't feed the gut, it adapts. It starts to slow down. So, when you do want to eat, let's say, during exercise, if you're a marathoner, for example, and you want to feel during a race, but you've been restricting carbohydrate, you've been restricting overall energy intake, stuff is just going to probably stick in your stomach longer than it normally would. 


There is a study I saw a couple years ago where they just surveyed high-level cross-country athletes and asked them how many times did they pass a stool per day, per week, and it was like twice a week with the average of something – don't quote me on the exact statistic, but it was something shockingly low. 


And there's certain athletes, understandably, are concerned about their weight management and body composition. But if you're restricting so much to the point where it's starting to impact your gut function, that can be certainly counterproductive to fueling especially during exercise and competition when you might want to try and consume some carbohydrate. Because your gut, it really hasn't been exposed to as much as it should. And the gut adapts to what you put in it. So, if it hasn't been getting a lot of carbohydrate, and then you all of a sudden trying to ingest a fair amount of it, it's probably not going to go all that well. So yeah, certainly, you could tie it to a little bit of an energy deficit in sport under fueling, because a lot of times it is under fueling of carbohydrate. That is the main problem.


[00:49:21] LB: You used the word adapt. And I'm aware that we've got very little time here. And of course, I want people to read your review. That's where they'll get the main points about specific supplements and so on, on this topic, and our previous podcast, and your book, and other papers, and so on. But that word adapt, I guess, there's two things in my head that I don't want to end this podcast without having gotten into, is this concept of how the gut adapts and potentially how we can train the gut to adapt, particularly as it relates to carbohydrate issues. But also, aligned to adapting is the concept of a gut reaction to something, which you of course is something that that can happen. You've pointed out, the gut is a sensory organ, and it can be very sensitive to certain things. So, you can help me make sure we don't forget those two topics.


But on the concept of adapting – because with athletes, we're very used to the idea of training adaptations to one's physiological systems, cardiovascular system, strength, power, and so on. But we don't always necessarily think so much about training metabolism, or training the gut in particular. What are your perspectives on working on adaptations of the gut and how that actually can be a strategy?


[00:50:37] PW: Yeah, it's an area that is getting more attention. And I've got mixed feelings about who and when it's useful to really purposefully train the gut. Because when you use the word train, and when I use the word train, it really is intentional. You've got some sort of goals in mind. You actually have a strategy in mind. So, that sort of rigorous form of eating I think is really probably only useful for certain set of athletes during their actual training. 


So, if we focus in on what are you eating during exercise to make your gut more accustomed to fueling? The degree to which you're going to actually practice that, train that, is dependent on a lot on how much you expect you're going to be consuming during competition. In some athletes, their sports just don't demand that they consume all that much. So, I don't know that they need to really spend a whole lot of time thinking about it, honestly. 


Sure, you want to practice like what you're going to do. I think that's true of anybody. But actually, like intentionally training the gut to handle more food, for example, or more carbohydrate, or fluid, really is probably for a subset of athletes that are doing more longer duration things that they're pushing the boundaries of how much fluid and carbohydrate they can really ingest. And modern marathon, the Tour de France, those situations, those are examples of athletes who might be eating 90, to 100, to 120 grams of carbohydrate per hour. And if you're going to do that, you probably want to actually spend some time specifically training your body to handle that. 


But outside of those like really specific situations, where you are feeling at that level of aggressiveness, I would just say practice what you're going to do. Practice and use the products you think you're going to use. Make sure you don't react to them negatively. Make sure you feel like you can actually ingest them at the exercise intensities that you're going to be competing at. Because sometimes people try these things, but it's at a low intensity. And that doesn't necessarily mean you're going to be able to handle that at a game intensity. 


But in those other situations where it's just lower amounts, I think, yeah, you want to try it out. But you don't need to go crazy with an actual gut training protocol. I think that's should be reserved for probably, again, a smaller subset of athletes who are really trying to push the boundaries of feeling.


[00:53:04] LB: Yeah, great. And this idea then of a reaction. You mentioned trots. Of course, runner's trots. I've been to many lectures where they've actually gotten the photos. Or if you YouTube this stuff, you can see some pretty horrified athletes go through that experience. But it is a real thing. But the reactions aren't necessarily as extreme as that. But nonetheless, there can be reactions to nutritional interventions, and strategies, and so on. If you could just quickly tell us about that and what we should bear in mind as far as the evidence is concerned.


[00:53:40] PW: Yeah, I mean, reactions could be any number of things, I guess. I mean, it could be ingesting a product that has a sugar in it or something that maybe you don't absorb particularly well. That could be athletes who are maybe ingesting a lot of lactose close to exercise. Because athletes have to, number one, a lot of times, fuel more than the average person. Eat more than average person. And sometimes the products that you might be eating like milk, or yogurt, or other supplements that might have lactose in it, or certain sugars that, at least in large amounts, your gut might have a little bit of a hard time actually digesting. That can be an example of kind of “a reaction”.


So lower FODMAP intake close to exercise would be a way to maybe deal with that. FODMAPs are the sort of short chain carbohydrates like lactose and fructose that, at least in large amounts, some people don't absorb all that well. So, that would be one example of a reaction. I mean, otherwise, it could be just a reaction to the consistency, the flavor, the texture of whatever product that you're ingesting. I mean, there are literally thousands of sports products out there. And when people asked me like, “What about this one and this very specific brand?” And it’s, “You got to try it out? I don't know.” I mean, you got to try it on yourself. There's no way for me to know really how you're going to respond to it. As much as I think someone wants just like a very simplistic, “Yes, this is a good product.” You got to really trial it out because of all the combinations of flavors, product consistencies, other ingredients that are added in. So, there is a chance that someone might have a reaction to a product, whether it’d be the sugar in there, or something else. Could be the osmolality, or the concentration of the product, any number of things that could lead to some GI issues. So, that’s the thing, of using those products beforehand and testing them out.


[00:55:35] LB: Yeah. And that's where I was sort of going to bring this end, is the triggering of GI symptoms by ergogenic aids. We're talking about supplements anyway. But ergogenic aids are – There are various kinds of ergogenic aids, which you can tell us about. You've covered a number of them in your review here. What are going to be the main sort of products that athletes are likely to take as ergogenic aids that could trigger GI symptoms? And what would be your main takeaways from that as far as the evidence is concerned?


[00:56:04] PW: Yeah, the carbohydrate one we talked about already fairly extensively. The other ones would be caffeine, sodium bicarbonate. And for those two – caffeine, of the two, is obviously much more commonly used. And usually, it's a problem of dosage or sensitivity, individual sensitivity, or the situation in which an athlete is deciding to use caffeine. 


So, doses above 500 milligrams more consistently produce GI issues, especially nausea. If you are going to be doing a workout or you're competing, I would take a look at the dose. Make sure that you're not overdoing it. And look at the other factors that could also be worsening the stress response. So, are you fasted? 


And by stress response, I’m kind of meaning like the stress hormone release. So, catecholamines, adrenaline. When you fast and you don't eat, those hormones are secreted to release fatty acids so that you can use fatty acids, and release glucose from your liver so that you can have a fuel source since you haven't eaten in a while. So, if you fast for a while, you ingest a bunch of caffeine, and then you try and go do something hard, it's more likely you're going to have symptoms like nausea. 


So, especially if you're combining caffeine sources, like you drink coffee in the morning, and then two hours later, you're ingesting an energy drink, you didn't really eat honestly all that much food. And then you go and work out, and you're experiencing these GI symptoms. That's probably a potential culprit you want to look at, is the amount of caffeine that you're ingesting. 


Beyond the dosage, there is, like any other supplement, individual responsiveness. And I think that's especially true of caffeine. People have wildly different responses to how well they tolerate caffeine. I'm a type of person that has to moderate caffeine intake, because it makes me anxious if I ingest too much a bit, especially in the morning. I wake up. I've already got like a general baseline of morning anxiety that tends to dampen over the day. But I don't need full strength coffee, two cups in the morning, on top of that. I will tend to drink some caffeine in the afternoon for a pick me up. But it's usually like tea. 


So, personally, I avoid high caffeine doses on like the morning of a race, because I know it doesn't really work well for me, despite all the evidence that says caffeine is supposed to be an ergogenic aid. So, yeah, I think individual responsiveness is a big piece. My guess is there's some genetic genes that dictate how much GI issues people have with caffeine. But those haven't really been identified yet. But that would be my guess, is that there are some genes related to how well people respond to caffeine. 


Sodium bicarbonate, also very evidence-based. But it's a very small percentage of athletes that ever really even use it, in part because of the side effects. I recently decided to supplement with sodium bicarbonate just to see what it would do for me personally. And then just had to have more of a first-hand experience that I could talk about with my students and with others. So, I ended up using enteric coated capsules. There's been a few studies in the last few years here that looked at using those types of capsules as a way to mitigate some of the GI symptoms. And overall, it worked pretty well in that regard. Like, I didn't have many GI symptoms. 


The downside is it's a lot of capsule. Like, relative to taking a powder and dumping it into some fluid, I'd have to go back and look at the number of capsules. But it was a lot. And I did a chronic loading regimen where I did for a few days kind of spread the dosages out over the whole day. And I think it ended up being like 20 capsules a day or something like that. 


Now, if you're going to do that acutely, you'd have to ingests 15 to 20 capsules a few hours before exercise. So, that's why I chose to do it over multiple days, is I'm like, “This is not realistic for me to actually ingest these many capsules two hours before my event or whatever.” So, that's one approach. 


But there are not a huge number of companies that make that. There's one in the US. I think it's called Bicarbi is the name of the product. I'm not affiliated with them or anything, but that's one that I used. And then beyond that, doing the chronic multiple day thing. Instead of taking one dose, let's say, a few hours before exercise, you spread it out in smaller dosages over several days leading up to the competition, and then stop maybe a few hours beforehand. And doing that chronically, you can usually maintain a good level of bicarbonate in the blood that'll help you perform. 


And then eating some carbohydrate with it if you're going to use the acute dosing protocol might help. I think there are enough ways to really mitigate the GI symptoms that I think it's an underutilized supplement to degree. But I understand the hesitancy of athletes to not use it because of the worry of if it does go wrong, it can go wrong horribly. So, I think you can mitigate it pretty well. But you would want to trial this out to make sure that whatever protocol you're using works for you.


[01:01:12] LB: So, look, we've talked a lot about these things, supplements, the gut, some went down a few rabbit holes, which I always love to do in these podcasts. But all in all, it's been a really fascinating conversation. Patrick, as always, you clearly know your stuff. And it's refreshing to hear your skepticism in certain areas, but also where you're clearly openminded enough. Also, I think it'd be interesting to know what your thoughts are about the future perspectives on this topic. Where you're going, but where you think as a whole, we should be going with this?


[01:01:47] PW: Yeah, there's a lot of areas that can be looked at. I mean, one of the caffeine ones, since we're just talking about that a couple of minutes ago, is maybe using alternate delivery formats instead of ingesting the caffeine. There're options to chew caffeinated gum. Caffeine mouth rinsing. I had a PhD student do a systematic review on that topic a few years ago. And there's not overwhelming evidence that it's helpful. But I think for people who are sensitive to caffeine, are there other ways we can deliver it that have less GI side effects implications? So, I'll be interested to see where that goes. 


Along the lines of some of these other supplements, for example, sodium bicarbonate. Just trying to honestly figure out a way to get athletes to be more willing to use it. I mean, I don't know if – that's not exactly studying the efficacy. But it seems like a supplement that a fair amount of athletes could have some modest benefit from. Not overwhelming. But how to translate that to actually more real-world use. And to understand what are the hesitancies? Is it just they don't know it that's a supplement you can use? Or is it they actively are avoiding it because of the side effect profile? 


And I don't honestly know the answer to that. I think it's probably a mix of both. I think a lot of athletes just don't even really know. They think, “What? Baking soda? Why am I ingesting baking soda?” But part of it might be they've heard that it has nasty side effects. So, if we think that it's a worthwhile supplement to use, how would we potentially get athletes to use it more often? For those who are interested. Not pushing supplements on individuals who don't have any interest in using them. But for those who are looking for some sort of edge and want to try something, that is an option.


[01:03:30] LB: Well, at the end of the day, you have to dig into all of the knowledge, the evidence and try and get the perspectives from the right sources, which for me is things like, on this topic, your review paper. And actually, having a conversation with people like yourself who have spent a hell of a lot of time trying to tease out the actual answers to these really quite difficult to answer questions. 


But I am sure that the audience have found this of great value. I will link in the notes to this review and some of the other relevant papers, etc., that you and colleagues have written to, written about. And of course, your book, which is still absolutely a must have, as far as I'm concerned, is on my shelf right behind me, as you can see. 


But I just like to thank you for your time once again, Patrick. And I look forward to bringing you back at some point when we have some other things to talk about.


[01:04:22] PW: Yeah, it's been a pleasure, again, to be on the We Do Science podcast. And I really appreciate the invite.


[01:04:28] LB: Thank you very much, Patrick. 


[01:04:29] PW: Thank you.