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Training the Gut, with Asker Jeukendrup

Pioneering sports nutritionist Asker Jeukendrup joins us for a discussion on how in-race nutrition is trainable and why you should be training your gut.

WorldTour peloton racing

Just ask any Tour de France rider who’s frequently burning 5000 calories or more per day about in-race nutrition and they’ll tell you that it’s both critical and tricky to get right.

You can spend months getting your legs ready for your target event, you can be putting out the best numbers of your life, and that can all be wiped away by a poorly timed bonk or intestinal cramping. You have to consume enough carbohydrates to keep the legs ticking over when the race gets hard, but at the same time you need to make sure they are well tolerated and you’re able to absorb them.

It’s a tricky balance and it’s highly individual. Simply buying the newest, coolest sports nutrition product isn’t going to get you there. You have to find what works for you.

But just as importantly, you have to remember that in-race nutrition, just like almost all things, is trainable and while you’re out three doing your big weekend ride, or hard hill repeats, you need to dedicate some time to training the gut.

So, today we’ll dive into nutritional training and talk about:

  • Applying a scientific approach to figuring out your carbohydrate needs and whether you are a fat burner or a carbohydrate burner.
  • Second, G.I. distress. Some thoughts on what causes it and why intestinal permeability may be a factor.
  • Next, we’ll discuss race nutrition and why changing up what you eat on race day may not be your best strategy.
  • Fourth, why most people can only absorb 60g of carbohydrates per hour but we’re still recommending trying to get 90g. That sounds like a lot, but it’s actually only about 360 calories which is still less than what you’re going to burn in an hour during a big race.
  • The best mix of carbohydrates to improve absorption
  • Why you need to dedicate time every week to training your gut – no different from the time and energy you invest in training your legs.
  • Finally, we’ll talk about any potential health concerns with focused race nutrition and briefly touch both on the microbiome and l-glutamine

Our primary guest today is none other than Dr. Asker Jeukendrup, one of the most renowned sports nutrition researchers in the world. He was editor-in-chief of the European Journal of Sport Science. He ran the Gatorade Sports Science Institute back when it was the center coaches and team managers were looking to for the leading hydration research. Now, Dr. Jeukendrup has his own company, Mysportscience, and works with Team Jumbo Visma.

Along with Dr. Jeukendrup, we talked with Katie Compton, the winner of 15 consecutive national cyclocross titles, and a four-time silver medalist at ‘cross worlds. She’s familiar with G.I. problems during races and shared with Chris some of her thoughts.

Next, we checked in with Colby Pearce, at this point our unofficial third regular on Fast Talk. He had some warnings about getting too caught up in traditional sports nutrition products and emphasized the importance of also considering health.

Finally, we touched base with Ryan Kohler, the head coach at the University of Colorado Sports Medicine and Performance Center. Ryan frequently works with athletes on training their guts for their target events and shared some of his strategies.

Primary Guest Dr. Asker Jeukendrup: One of the most renowned sports nutrition researchers in the world
Secondary Guests Katie Compton: 15-time cyclocross national champion Colby Pearce: Coach and bike fitter Ryan Kohler: The head coach at the University of Colorado Sports Medicine and Performance Center

Episode Transcript

Intro  00:00

Welcome to Fast Talk, the VeloNews podcast, and everything you need to know to ride like a pro.


Introduction to Training the Gut

Trevor Connor  00:13

Hello, and welcome to Fast Talk. I’m your host, Trevor Connor, along with my co-host the Italian Stallion, VeloNews. Managing Editor Chris Case. This is an episode that Chris has been excited to put together for a long time. Since he’s leading a tour in Italy right now, you are stuck with me doing the intro. Just ask any tour rider who’s frequently burning 5000 calories or more per day about in-race nutrition, and they’ll tell you that it’s both critical and tricky to get right. You can spend months getting your legs ready for your target event, you can be putting out the best numbers of your life, and that can all be wiped away by a poorly timed bonk or intestinal cramping during the race. You have to consume enough carbohydrates to keep the legs ticking over when the race gets hard, but at the same time, you need to make sure that they are well tolerated and you’re able to absorb them. It’s a tricky balance, and it’s highly individual. Simply buying the newest, coolest sports nutrition product isn’t going to get you there, you have to find what works for you. But just as importantly, you have to remember that in-race nutrition, just like almost all things is trainable, and while you’re out there doing your big weekend ride or hard hill repeats, you need to dedicate some time to train in the gut. So, today we’ll dive into nutritional training and talk about applying a scientific approach to figuring out your carbohydrate needs and whether you’re a fat burner or a carbohydrate burner. Second, GI distress, some thoughts on what causes it and why intestinal permeability may be a factor. Next, we’ll discuss race nutrition and why changing up what you eat on race day may not be your best strategy. Four, why most people can only absorb 60 grams carbohydrates per hour, but we’re still recommending trying to get 90 grams. That sounds like a lot but it’s actually only 360 calories, which is still less than what you’re going to burn in an hour during a big race. Fifth, the best mix of carbohydrates to improve absorption. Why you need to dedicate time every week to train your gut? No different from the time and energy you invest in training your legs. Finally, we’ll talk about any potential health concerns with focus race nutrition and briefly touch on both the microbiome and glutamine. Our primary guest today is none other than Dr. Asker Jeukendrup. Doctor Jeukendrup is one of the most renowned sports nutrition researchers in the world, he was editor in chief of the European Journal of Sports Science. He ran the Gatorade Sports Science Institute back when it was the center coaches and his managers were looking to for the leading hydration research. Doctor Jeukendrup now has his own company, My Sports Science, and works with Team Lotto NL Jumbo. Along with Dr. Jeukendrup, we talked to Katie Compton, the winner of 15 consecutive national titles and a fourth time silver medalist at Cross Worlds. She’s familiar with GI problems during races and shared with Chris some of her thoughts. Next, we checked in with Colby Pearce, at this point, our unofficial third regular on Fast Talk. He has some warnings about getting too caught up in traditional sports nutrition products and emphasized the importance of also considering help. Finally, we touch base with Ryan Koehler, the head coach at the University of Colorado Sports Medicine and Performance Center. Ryan frequently works with athletes in training their guts for the target events and shared some of his strategies. All right, pull out your Swedish Fish, throw them in the trash, and get some real sports nutrition, and let’s make you fast.


Trevor Connor  03:48

This episode of Fast Talk is sponsored by WHOOP. The thing I found really interesting with this is 90% of the time that WHOOP strap gets you right, and certainly with me, I average four to five hours of sleep a night, so just every morning would say you’re an idiot. I guess. But there’s that that 10% of the time where it tells you something different from what you’re feeling.


Chris Case  04:11



Trevor Connor  04:12

So, my initial reaction is I really know myself, so the WHOOP strap is wrong, but I actually was surprised how many times I then went through the day and when actually,


Chris Case  04:21

It’s right,


Trevor Connor  04:22

It might have been right there. WHOOP is the performance tool that is changing the way people optimize their training recovery. WHOOP provides a wrist-worn heart rate monitor that features detailed app-based analytics, and insights on recovery, strain, and sleep. WHOOP tracks sleep quality and heart rate variability 100 times per second, 24-hours per day, to help you know when your body is recovered or when it needs rest. You could also use the strap to track workouts and get strain score, so that you know how strenuous the training was on your body. WHOOP helps you optimize your sleep based on how fatiguing your day was and track sleep performance with insights into sleep quality, stages of sleep, and consistency. To make things better, WHOOP just released a new WHOOP strap 3.0, which includes a suite of new hardware and app features. The WHOOP strap 3.0 now has five-day battery life, an approved strap, and live heartrate monitor. A handful of new in-app features including the new strain coach, improve the way you track and plan your training and recovery. WHOOP provided an offer for Fast Talk listeners to get 15% off their purchase with the code “fasttalk,” just go to, and use the code “fasttalk” at checkout to save 15% off and optimize the way you train.


Trevor Connor  05:53

So, Chris, I can tell you I’ve had a bunch of listeners contact us with questions and I keep hearing the, love listening to your show while I’m out on a ride.


Chris Case  06:01



Trevor Connor  06:02

Which actually admittedly had me a little bit concerned, and so I actually reached out to AfterShokz because of this, because I feel I need to promote safe riding.


Chris Case  06:11

Yeah. And you’ve been using them for years.


Trevor Connor  06:13

I’ve had them for four years, and I love them because they actually sit outside of your ear so you can listen to music, you can listen to Fast Talk,


Chris Case  06:22

You can listen to what, Mariah Carey is your favorite, right? Celine Dion?


Trevor Connor  06:28

Why? Pick? Thank you. We have so many good Canadian beheads, why do you always go that?


Chris Case  06:36

Dave Coulier?


Trevor Connor  06:37

I don’t know who that is.


Chris Case  06:39

Cut it out.


Trevor Connor  06:40



Chris Case  06:42



Trevor Connor  06:44

The point being, you can make your Canadian music playlist which there is some good stuff out there, and you can listen on your ride and still hear your surroundings. These headphones don’t go in your ears, so you could hear the cars, you could hear what’s going on around you which for safety reasons, is something we really want to promote here at Fast Talk.


Chris Case  07:08

And there are the little buttons on there. So, you can mute, and pause, and fast forward, and rewind, very quickly.


Trevor Connor  07:14

That’s right, you don’t have to stop and pull over and grab your phone out of your pocket.


Chris Case  07:18

All Bluetooth.


Chris Case  07:20

This episode was sponsored by AfterShokz, the award-winning headphone brand best known for its open ear listening experience. Powered by Patented, best in class bone conduction technology. AfterShokz headphones sit outside your ear so you can hear your music and your surroundings. AfterShokz is a must-have headphone for cyclists providing the ultimate level of safety and comfort, without compromising sound quality. To learn more and save 50 bucks on AfterShokz bundles, visit, and use code “fasttalk.”


Introduction Dr. Jeukendrup

Chris Case  08:06

So, our guest today, Dr. Asker Jeukendrup is world-renowned for his sports nutrition sciences, his website that has a lot of great content on it, but he’s also a professor, he’s consulting with a lot of professional teams around the world. It’s a pleasure to have you on the show, we’ve been hoping to get you on for quite a while now, so I’m happy to have you finally on the show with us. Thanks for joining us, Dr. Jeukendrup.


Asker Jeukendrup  08:33

Thanks very much for having me. I’m glad it finally worked.


Chris Case  08:37



Trevor Connor  08:38

It’s an honor to have you on the show, so thank you.


Dr. Jeukendrup Background in Cycling

Chris Case  08:40

Could you give us just a little bit of a taste of your background, both your education and some of the work that you’ve done to get you where you are today?


Asker Jeukendrup  08:51

Sure. Yeah. I mean, I started this many, many years ago as a as a young kid who is interested in cycling, also a little bit of running, but mostly cycling, that was my favorite sport and I wanted to do something with it. I was a decent cyclist but not the best cyclist. But at one point I had to decide whether to go and try to become a professional cyclist or do something else with my career. I ended up at University, studying movement sciences, exercise physiology, really, and this was based on something that I’ve seen on TV, I’d seen a professional like speedskater, big sport in Holland where I’m from, and this world champion speedskating was also a professor in exercise physiology at the Maastricht University. This is when I knew that’s what I wanted to do. So, I went to that university, I ended up working with that Professor, and initially I worked on projects around overtraining. Then I stayed at that university did a Ph.D. in the department that had a very strong nutrition background with some big names in the field of sports nutrition. So, I learned from some of these, some of these big names, spend quite a bit of time and quite a few studies we did at Maastricht University, and then I spent a year at the University of Texas in Austin.


Chris Case  10:25

Yeah, that’s where I went my graduate degree in journalism, not in science, but I was down there for a while.


Asker Jeukendrup  10:31

Ah, right, maybe at the same time.


Chris Case  10:33



Asker Jeukendrup  10:35

And I think this is 97.


Chris Case  10:38

I was just a little bit after that. Yeah. 2003


Asker Jeukendrup  10:41

Yeah. So after, after that I am, I went to Birmingham, and Birmingham was a really good university, they didn’t have a huge sports science department, but I joined that, that department to set up something in sports nutrition. We started really small, we didn’t really have a lot of lab space or not any lab space when they started, and over the years this, the lab grew, and I had more and more people in my team, and we started to pursue some really good questions that a lot to do with carbohydrate delivery during exercise, GI problems, and those are some of the core topics that we worked on. So, then I became a full professor at the University of Birmingham, was in charge of the human performance lab there for many years, and then I tried something else after that, after that career, we’ve published many, many studies, and I just wanted to try something different. So, I worked as the head of the Gatorade Sports Science Institute for a little while, based in Barrington, Illinois, and we have labs in different places, also labs in Europe, labs in Mexico, but also lab, of course, in the in the US at various places.


Trevor Connor  12:05

What years were you running the Gatorade Sports Science Center?


Asker Jeukendrup  12:08

2011 to 2014.


Trevor Connor  12:11

Great research that has come out of there.


Asker Jeukendrup  12:14

Yeah. Well, one of the things I think that they do really well try to communicate the science, and work together with the scientists, and then in the form of their sports science exchange articles, make the information accessible for most people, and quite readable, shorter articles with good scientific and neutral information. Now after that, I started my own company, My Sports Science, and that’s consulting mostly with, with teams, athletes, organizations, companies sometimes, and it’s advising them mostly, mostly on performance, and many of the questions I get are around nutrition.


Chris Case  13:02

Jumbo Visma Included in that now?


Working With Team Jumbo-Visma

Asker Jeukendrup  13:04

Yes, yeah, they’re doing fairly well. So yes, they’re definitely part of this. On the nutrition front, we’ve done a lot of really, really cool work, I think it’s I think part of the team’s success is because they’ve been able to incorporate science at a really high level, they’ve found a way to really like translate it and get the whole team behind it. This is why in a lot of sports, it doesn’t quite work, even though the ideas are great, it’s the execution is usually very problematic, because you have to deal with a lot of people who actually make this thing happen. So, in cycling as the, is this one yours, and everyone around the team and the chefs or whoever liaises with the hotels, if they are not behind the ideas, or if they don’t really understand it, then you can have all the ideas in the world, but it never happens. So, we really started a couple of years ago, and we try to kind of approach nutrition from scratch, just starting to build from science rather than from what people were used to do. We just evaluate it, what are really the important the key things that we need to address? And how can we make it easier and how can we help the riders to do this? And so, we had a whole bunch of ideas and started to develop something in one of the sort of major stage races, and we tried to feed them according to a plan, according to what they would actually need. So, in theory, we calculated what they would burn during a stage in terms of calories, but also in terms of carbohydrate, and then we had a nutrition plan that aimed to replace that carbohydrate, make sure that they were an energy balance, and not gaining weight or losing weight, and we planned nutrition 40 stage races, maybe a couple of months in advance, we started to work with a company that prepared the food company in Holland, and the food was and shipped to the races. And of course, every rider then is an individual, everyone has a different energy expenditure, everyone uses a different amount of carbohydrate, and you really only know how much someone has burned once they’ve crossed the finish line and press the button on their computer. So, at that time, when they pressed the button, I would receive a message on my computer that they had finished, I could see the power files, and I could do a calculation manually, initially, on how much carbohydrate they had used. Then I would call back to the team and let them know how the estimation that we did, like months before how it needed to be adjusted, because maybe the stage was a little bit harder or maybe a little bit easier, and then they made the final adjustments in the evening meal. That was sort of the start, and the first time it is really wasn’t perfect, it was also a lot of work, a lot of people involved. So, then we started to do this in a little bit more detail with two riders in the Giro, and quite successfully, and the riders really liked it, they never felt hungry, they always felt felt strong. So, for them, this approach really worked, and they started to trust the system, the other riders soon followed. So, in some of the next race, we tried it with a larger group, and now we just do it with a whole team. We also work with a supermarket in Holland, which actually a sponsor of the team Jumbo, and they are developing some software that’s called, Food Coach. So, all the work that I was doing manually is now part of that software, and the software does all the calculations. So, as soon as the rider sort of press the button, there’s still a little manual stamp that we’ll fix as well, but as soon as we know the data from the day, we can then adjust the nutrition plans of the software then calculates exactly how much the riders need to eat. So, you can often find the riders with their mobile phones in their hands with the app open and the app just tells them how much they are supposed to eat of everything. It really seems to work and the riders really believe in it, and also the results are there I think.


Trevor Connor  17:54

So, got a question. I’m sure the listeners are wondering about is this the sort of app that’s going to be available to everybody? Or is this really just for the pro teams, top riders?


Asker Jeukendrup  18:04

Well, my question would be, is this something that everyone would need? And I don’t think it is. To be honest, I think this is something if you’re riding the Tour de France, it’s worth going into that much detail counting the calories, but to be honest, for the vast majority, even really good riders, I am not a huge fan of them counting calories, or maybe do it for short periods of time, so you get a good understanding of how much you’re eating or not eating. I’m definitely not a fan normally, of calorie counting, in big stage races is a little bit different, because there’s so much exhaustion, that hunger feelings are completely suppressed, and at the same time, you got to eat an average 6000 calories a day, and that that’s a really difficult task, and if your hunger feelings cannot guide you anymore, then you need some other help, and this is where the app can actually really make a difference.


Chris Case  19:08

Are these meals prepared and then like, are they frozen and then shipped? What are we talking about?


Asker Jeukendrup  19:16

So, the app is now developed that it works for meals in races where chefs travel with the team and they will actually prepare the food. So, the food is shipped to the races. So, we take our own food from the supermarket to these races, and then we have the chef’s that actually prepared according to the app


Chris Case  19:38

I see.


Asker Jeukendrup  19:40

It also works in the home situation, and then it just tells the riders what to cook and they can choose recipes, whatever they want to be on the menu they can select from a number of meals that fit in with what they need that day, and then yeah, they can select this and pick up the groceries at the supermarket or even have it delivered.


Chris Case  20:04

Yeah, I can imagine that not long from now there will be a drone flying to all the team member houses with the meal and all the ingredients they need to cook their meal, just landing right at their front door.


Asker Jeukendrup  20:17

We’re not quite that far yet. But that would be the next step, yes.


Trevor Connor  20:20

Yes. Amazon Prime delivery.


Asker Jeukendrup  20:28

Okay, but when you when you think about these things, you have to you have to think big, and you have to think a little bit outside the box and think too much about the restraints and all the things that make it really difficult to do, because if you get a good group of people together, you can actually make things work, and that’s one of the things that has definitely happened here.


Trevor Connor  20:51

So, when you’re individualizing, this, I’m assuming with all these athletes, you’ve got them in the lab before the race, and you’ve done the test on them to see what their fat and carbohydrate ratios are at increasing intensities, you’re using that to analyze their file each day?


Asker Jeukendrup  21:09

Yeah, I mean, that’s sort of the logical way to do this. Although, even if you do a lab test of say, one hour, that sort of data is very difficult to extrapolate to a five-hour stage in the Tour de France, of course. So, all the tests would give you is a pretty rough estimate, and probably a very good starting point. What you end up doing is probably a little bit trial and error, and this is something that we’ve learned we. We got right the first time for a number of riders, but a number of riders also were very hungry when we used the same equations for them. So, these equations of what they need really need to be adjusted to the person and some of it, you can maybe based on signs or try to based on signs, but some of it is just simply trial and error, and once you’ve sort of nailed the algorithm, it’ll just always work on that person, I think


Trevor Connor  22:09

I’ve never seen a study on this, but I have to believe that at an event like the tour, over the course of the event, these athletes are just going to become fat-burning animals, because it’s just so hard to keep the glycogen stocked up.


Asker Jeukendrup  22:23

Yeah, I mean, I haven’t seen that study either. So, I can’t really base this on any scientific evidence, but I would actually expect that whether someone is a fat burner or not, is is largely genetic. From my experience, I’ve seen that people are either good fat burners, or they’re either really good carbohydrate burners, and there are also some people who sit somewhere in between, but usually they fit into one of these two categories, and clearly, they’re all riding together in the pro peloton. So, it’s not directly affecting performance, but it may affect what they actually need to fuel with, and I think, and this is also again, it’s not based on a lot of science, but it’s more experiences, it appears that if you measure the fat-burning guys, those are the ones that don’t really know what the hunger knock is, but the ones that are really good at burning carbohydrates, they know that feeling really well, and exactly what that is, I don’t know, it may relate partly to fiber type, although I wouldn’t expect a large difference in fiber type in, in a group of professional cyclists. So, there’s still a lot of questions that I also have about, why is it that the metabolism is so different? And and also, why is it that even though it is that different, they’re all riding together, and their performance is very similar?


Trevor Connor  23:59

The immediate reaction I had is when we talk about the differences within humans, at the end of the day, or we’re all aerobic animals, none of us are prepared to do what you see in the wild, true strength, pure anaerobic beasts. So, I guess it’s all relative.


Asker Jeukendrup  24:18

And then we are talking about professional cyclists, and they are really all at one end, or the extreme end of that spectrum. So, even if you have this, like a group of kind of aerobic animals, right? Like the professional cyclists will all sit at the very far end of that of the spectrum.


Trevor Connor  24:38

Yeah, which is kind of what I was getting at. You can talk about the difference between the tour sprinter and tour time trialist, but you compare him to 100-meter sprinter on the track, and it’s those two cyclists really aren’t that different.


Asker Jeukendrup  24:50

Yeah, correct.


Causes of GI Distress

Chris Case  24:51

Let’s dive into that big topic of GI distress. Can you give us a Starting point of the causes of GI distress?


Asker Jeukendrup  25:03

Yes, although that’s actually a very difficult question, because I don’t think we actually know a lot about the causes, we know a lot of factors that increase the risk of getting GI distress, and some of those factors are nutritional, but actually, most of those factors are non-nutritional. We know for example, that runners suffer more than cyclists. So, and we think that that has something to do with the up and down movement, which means that also the GI system will move up, and maybe somehow that causes some GI distress. We know that women have more GI problems and men, for reasons we don’t really understand. We know that the food intake, the days before races seems to have an effect on whether people develop GI problems or not. So, there’s a number of factors that we know relate to GI problems, but in terms of the actual causes, why do we get GI problems when we start to exercise? And why don’t we get it in training? Because a lot of people have no problems and training, but then they go to races, and suddenly they have all of these problems. There are also people who have this every long training. Why is that? So, the only like real theory that has developed is around blood supply to the GI system. There is of course, a redistribution of blood flow, as soon as you start exercising, where skin and muscle will get more blood, and there will be less blood, therefore available for the GI system, and maybe that causes suboptimal performance of the GI system. That is one theory. But to be honest, there is not a huge amount of evidence that that actually happens, there are maybe two or three studies that I’m aware of that have measured something in that direction, but it’s also really difficult to measure. Like everyone seems to have their own pattern of problems, and that pattern is fairly reproducible, but it’s really different from one person to the next. Why? I’m not sure. So, yes, and it’s a real problem, because I mean, maybe in cycling a little bit less so than in running and in triathlon, it’s extremely prevalent. If we look at the studies, then we can find anything between 30 and 93% of prevalence. So, there are races where 93% of the people report some sort of problem.


Chris Case  27:48



Asker Jeukendrup  27:50

This is probably because of the way these studies are set up, and the questions are asked, right? Because not all of these, and I think if it’s 93%, then the question was probably did you have any GI problems? Or did you have any of the following issues? And some of those issues are really non-severe, but they could be classified as GI issues. What we’re really interested in those issues, of course, that that affect performance and have a negative effect on performance or even health.


Trevor Connor  28:24

He brought up that 93%, and so that’s actually from your 2000 study, and it touched on something that I personally found really interesting, which was there does seem to be some sort of correlation with endotoxemia.


Asker Jeukendrup  28:40



Trevor Connor  28:41

Basically, the symptoms that these athletes are seeing are somewhat similar to sepsis.


Asker Jeukendrup  28:46



Trevor Connor  28:46

So, Chris endotoxemia is when you see some of the contents of the gut. So, particularly something called like lipopolysaccharide (LPS), which is on the bad bacteria in your gut gets into circulation.


Asker Jeukendrup  28:58



Trevor Connor  28:59

That causes a reaction that causes a lot of these symptoms that you see. If it gets really bad that leads to sepsis, and when you look at the symptoms of sepsis, and you look at the symptoms that these athletes were reporting, they’re very, very similar. I noticed your study showed that 79% of the people who were reporting GI problems also had elevated LPS in their in their bloodstream, but you didn’t see that even though there was a correlation, the symptoms didn’t come on with the elevated LPS. Is that right?


Asker Jeukendrup  29:31

Yeah, that’s right. So, I mean, maybe should go one little step back is that this is all measured during an Ironman distance triathlon. So, if a long-distance event where the finishers were between 11 hours and 16, if I remember correctly, or 15 hours, so it’s a very long-distance event in really extreme conditions. So, this is in the, there’s a huge of altitude difference and in race, and the conditions are extremely hot. We’ve picked that on purpose because we wanted to measure in the most extreme situation, and in that most extreme situation, the theory was exactly what you described, right? So, the guts stops to function normally, it normally has a very important barrier function, if that barrier function does not work appropriately, it means that bacteria could enter the body with all sorts of negative consequences. We did see some elevations, but nothing that anyone in a clinic would actually be alarmed from. So, I think the main conclusion of the study was that maybe like, even in that really extreme situation, it probably is not bacterial translocation that causes all these problems that people have, but it’s still one of the theories that’s out there. We were triggered by another study, where they showed, like very large amounts of bacterial translocation in runners. So, we like that the first or maybe the most important conclusion was that we couldn’t confirm those results from that study, and what we think is that I see the experts that we worked with, on bacterial translocation, they believe in that study there, because there’s a field study, it’s very difficult to not contaminate your samples, and the slightest contamination can give the results that they had, and we were really careful not to contaminate the samples and, therefore, didn’t see like the same magnitude of response that they had. So, personally, I think it can happen, I think it will happen in really extreme situations, but I don’t think that this is the reason why people have GI problems. Also, because a lot of the GI problems happen well before any bacterial translocation would occur.


Trevor Connor  32:24

Well, it’s interesting, because like you said, it’s something that people are still researching. I don’t know if you saw, so just this January, a study in PLOS that looked at at triathletes, and it was actually looking more at intestinal permeability. So, they were measuring a marker permeability called zonulin, and Chris has given me that look.


Chris Case  32:44

I love it, nerd bombs.


Trevor Connor  32:46

You get excited when I search around these terms out? So, they did find a correlation between intestinal permeability or the zonulin levels, and they found that correlated with muscle damage. So, you know, there wasn’t a home run study of here’s the cause of all the GI stress, you know, they saw some of the same things as you, certain markers that they expected to elevate, didn’t elevate. But they certainly did see that correlation with intestinal permeability.


Asker Jeukendrup  33:17

It is, of course, important to realize that correlation doesn’t mean causation, right? So, sometimes you find correlations, but the two things have very little to do with each other, other than in this case, maybe like hard exercise cause both. But the two don’t necessarily need to be correlated.


Chris Case  33:39

If you were asked to speculate, I’m going to ask you to speculate, with the absence of concrete evidence what do you think is the mechanism here that causes this? Is it a host of things?


Asker Jeukendrup  33:54

I think it’s a host of things, and this is the reason why there’s such a wide variety of symptoms. I think the main cause, must have to do something with the sort of the innovation of the GI system. So, it’s, in terms of neuro innovation, it’s one of the most dense tissues, there’s a lot of neurons in the in the GI area, and this is probably why in stressful situations, races, for example, we see some of these problems much more profound, in training situations you don’t see them at all. So, I think the fact that there are so many neurons, that has something to do with it, it also makes it really difficult to address it because training stress or race stress is raised stress. Not only easy to reduce. So, I think that is one of the main reasons, especially if people have these problems with races, but not in training.


Chris Case  35:12



Asker Jeukendrup  35:13

In other cases, I think it is related to nutrition, just like sometimes just poor nutrition choices, sometimes it is, yeah, just not knowing, not knowing that for you, maybe fiber intake the days before can have an effect on GI problems, and this is a very common factor. Another one and this one is also not well described in the literature, is lactose intolerance. Some people are lactose intolerant, they usually know it, and they avoid dairy products, but other people never see the symptoms of a very mild lactose intolerance, or maybe that lactose intolerance actually becomes a little bit more severe during exercise. So, those are the people that would benefit from reducing or removing dairy products days before the race. This is not very well described in the literature, but it’s certainly my experience that if you just for some people reduce dairy products days before, it can completely solve their GI problems, and the same is true for fiber. So, some people if they just remove fibers from the diet two days before the race, sometimes that completely solves their GI problems.


Trevor Connor  36:34

Katie Compton is arguably one of America’s greatest cyclists, having won the National cyclocross championships 15 years in a row. Like many cyclists, she hasn’t been able to escape GI issues. Chris talked to her about this, and just how individual nutrition and gut issues really are.


Katie Compton: Individual Nutrition and Gut Issues

Chris Case  36:50

So, I don’t know if this is a rabbit hole that we want to go down, But


Katie Compton  36:55

It’s a deep rabbit hole, if you really want to go down that one.


Chris Case  36:59

No offense, but you’re a-typical, I think.


Katie Compton  37:02

I am. Yeah, and I’ve read a lot about nutrition, I’ve also tried quite a few things from my own personal just interest, and to see what works, also through coaching a lot of people for a long time, every single person is different, and one nutrition program that works for one athlete doesn’t work for the other. I’ve also found that to and some athletes can eat a ton of carbohydrates and digest it and I have an issue, some people can, you know, eat massive quantities of fructose and digest it just fine and not have any stomach cramping. But the majority of people can’t actually get away with it, and so I feel like each athlete needs to figure out what works for them, and it’s a lot of trial and error and a lot of looking at research and like, well, let’s try this, let’s try that and see what works. If it doesn’t work, let’s move on to something else until you can dial in what works for you as an athlete. Also knowing that what works for you when you’re 20 doesn’t work with you when you’re 30, and when you’re 40, it’s going to constantly change and food allergies develop over time, seasonal allergies get kind of worse over time. So, it’s definitely something that’s dynamic, I feel like you need to listen to the body and see what it needs. If you’re having food issues, digestive issues, why what have you been eating that might be different, or might just all of a sudden start affecting you? Because I didn’t have any allergies until I 30, my mid-early 30s or early, mid-early 30s, I think it’s when I first start having issues, before that I could eat whatever I wanted, it didn’t matter, minus folic acid, but like, it was great when I could eat whatever, and now I’m just like, ah, why does this bother me too?


Chris Case  38:34

Yeah, I bet it is frustrating.


Katie Compton  38:37

Yeah. But like now I dial it in, and I actually feel really good. I eat a variety of foods and foods that work with me, and I don’t have any issues anymore. But that’s also taken a lot of trial and error and figuring out what works for me. But yeah, I have heard the carbs, especially like, the Dutch have an uncanny ability to absorb and metabolize carbohydrates more than a lot of cultures in the world. So, yeah, and I read David Epstein’s, The Sports Gene, and I think that’s where because he went through all the cultures in the world and the nutrition and different cultures, and how some individuals can digest certain foods better than others. I remember that the Dutch could digest carbohydrates better than most any other culture. So, yeah it depends on where you’re from and what your genetics are.


Chris Case  39:25



Katie Compton  39:26

Realize necessarily.


Nutrition and Races

Trevor Connor  39:29

Let’s get back to the show and talk about nutrition and races.


Trevor Connor  39:33

So, this is a fairly old and simple explanation, but certainly one that’s been proposed before is that you have athletes when they get to race day, they change how they eat, you know, they have that philosophy of well, you know, the group ride on Saturday is one thing, but the race is another thing, and suddenly in the race, they’re over-focused on getting every gel into their system that they can get into their system, meanwhile, at the same time, as he said, because it’s very intense there’s less blood flow to the gut. So, you essentially have more carbohydrates, more fuel, hitting their gut when their gut isn’t functioning well than they’re used to. So, you start having some fermentation issues potentially, you particularly have an issue of that highly concentrated, probably sodium and carbohydrate mix in the gut is drawing fluid into the gut out of circulation, and I know this is a very that Dr. Stacey Sims is promoted, and those two things are causing some of the bloating and gas that people experience. Is there any validity to that in your opinion?


Nutrition Mistakes

Asker Jeukendrup  40:38

Yeah, absolutely. I think this is what I was referring to as nutrition mistakes, especially during races or during training. This is, this can be a real cause. But I think it’s got to be extreme, and with extreme, I mean, it’s got to be extremely different from what you normally do. Now, if someone always trains with just water, never takes any gels, never takes any carbohydrate on board, then it is pretty quickly extreme, your gut is not used to seeing gels. So, it’s yeah, it’s not surprising, I think that if you then suddenly start to take large amounts of gels, and especially if you don’t take a lot of water with that, then that can easily cause GI problems. This actually has been discussed in the literature, so there is a clear correlation between high carbohydrate intake, high carbohydrate drinks, with like really concentrated drinks, or gels, and GI problems. But usually, these are problems of the upper GI tract. So, it’s usually stomach related stomach cramping, bloating, and usually a little bit less sort of diarrhea, and these problems are also usually a little bit more acute, and it’s simply because if the carbohydrate concentration in your gut is too high, then your body will start to dilute that content and keeps it in the stomach for a little bit longer, until it is actually diluted. So, you’re just slowing things down if you take too much carbohydrates too soon, with too little water. Now, having said that, there are situations I think where it is really appropriate to do that if we’re looking at colder conditions where the carbohydrate need is quite high, in those conditions, it is I think, appropriate to take more carbohydrate and less water on board. As a guide, we developed a piece of software for people to use. I hope that’s okay to mention, the software is called, The Core, it can be found on It’s free to use, but we use the scientific evidence that is in the literature and came up with nutrition advice where we separate more or less the fluid advice from the carbohydrate advice and then put the two together. So, the fluid advice is based on sweat rates, and it is also based on a certain amount of fluid that is okay to lose, there is no need to drink as much as you sweat, it is okay to lose some body weight. But there is a point where you’ve lost so much body weight and you’ve lost so much fluid that it’s going to impair performance. So, it’s finding that balance, and a lot depends on the duration of the event and sweat rate. So, that’s the fluid side. The carbohydrate side, and this is something that we’ve shown in many studies, your carbohydrate needs are really dependent, mostly on the duration of the event. If the event is shorter, you need less carbohydrate, if the event is longer, you also need a higher carbohydrate intake per hour. In events over two and a half or suddenly over three hours, we would recommend 90 grams of carbohydrate per hour, and that’s quite a lot.


Trevor Connor  44:29

We need to ask you about that, because in your research talking about gut training, you pointed out that our, we can get into the glucose-fructose mix in a second, but he said maximum absorption rates tend to be right around 60 grams per hour, and there doesn’t seem to be a ton that we can do to increase that. So, how come you’re recommending 90 grams if that’s beyond what anybody can absorb?


Asker Jeukendrup  44:57

Yeah, so, I have to take you back a little bit in some of the studies that we did. So, initially, I was interested in this finding from all of our studies, but also many other studies that, whatever you did, we never saw absorption rates, or I should actually say oxidation rates because that’s really what we measure, of more than 60 grams per hour. So, even when we gave people 180 grams of carbohydrate per hour, ridiculous amount, they were still only using 60 grams per hour, and other studies found the same. So, gradually, you see an increase in exogenous carbohydrate oxidation, if you go from very small intake to 60 grams per hour, if you go over 60 grams per hour, it doesn’t really change your oxidation rates, it stays at around 60 grams per hour. So, I was kind of fascinated by that, by that finding. I thought, well, if we could find a way to increase carbohydrate oxidation, then maybe that can also affect performance, but how do we do that? So, we had to find a limitation to this. Why is it that you can only oxidize 60 grams per hour, and so we looked at gastric emptying and found, well, the stomach can empty much more than 60 grams of carbohydrate per hour, so that wasn’t the reason. We looked at uptake of carbohydrate by the muscle, and when we infused glucose directly into the blood, we saw that the muscle can take up much more than 60 grams per hour, so that wasn’t the limiting factor. In the end, we ended up with only one possible explanation, and that was the absorption. But if we picked up a textbook, then the textbooks would actually show us that well, the capacity for the guts to absorb carbohydrate is virtually unlimited. So, this, this idea wins all of the textbooks. So, we designed a study because glucose is normally transported through a transporter called SGLT1, as sodium-coupled glucose transport, and we believe that maybe that transport was limiting. So, if you give more than 60 grams of carbohydrate per hour, you saturate the transport and you just cannot get more carbohydrate into the body, a little bit comparable if you have a number of people in a room, and you open a door and you tell those people to leave the room as quickly as possible, it just depends on how wide the door is, how many people can leave the room, and it is the same I think with glucose.


Chris Case  48:00

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Trevor Connor  49:19

This is probably where it’s worth mentioning that fructose actually uses a different transporter, it GLUT5, so that’s one of the ways you can increase a little bit of your carbohydrate absorption.


Asker Jeukendrup  49:31

Yeah, that’s right. So, that would be opening a second door basically, and so that’s where we started to do experiments with combinations of glucose and fructose, where we gave enough glucose to saturate the SGLT1 transporter, and then we gave fructose on top of that, hoping that that would get across through the blood drive transporter. And in the first study, we confirmed Immediately, that was the case, and in that first study, we saw oxidation rates were about 30% higher than with a mix of glucose and fructose and with just glucose, and that was just the first study of a whole series where we tried to figure out, how can we optimize carbohydrate delivery? In the latest studies there, we found that we can even deliver carbohydrate at a rate that was 70% higher than we thought was initially the maximum that you could possibly achieve.


Trevor Connor  50:33

What’s sort of race? What’s their absolute quantities where you saw when you were increasing that much?


Asker Jeukendrup  50:39

In grams per minute, we found 1.75 grams per minute. So, that’s yeah, 75% more than one gram per minute that we thought was maximum.


Trevor Connor  50:50



Asker Jeukendrup  50:52

So, yeah, huge, huge differences simply by using a combination of different carbohydrates. We used glucose and fructose in the first study, we also tried different combinations, we tried glucose, sucrose, and fructose, we tried maltodextrins and fructose, which is actually what I would recommend because fructose is extremely sweet, glucose is really sweet, so the combination doesn’t give you a very palatable solution, even though it may be effective. But if you combine fructose with maltodextrins, then the taste is a little bit more tolerable. So, that’s a sort of practical solution, and we’ve also seen really good results in terms of oxidation with mixtures of maltodextrins and fructose.


Trevor Connor  51:41

So, I’m just going to do a quick health aside here, fructose in combination, when you’re exercising is fantastic, but it’s not something that you want to over-consume at rest, because first of all, fructose is actually processed by the liver, and it isn’t great limited. When you consume fructose, you maximally oxidize it. So, if your body doesn’t have a use for it, you’re going to start seeing big buildups of lactate and other issues that are going to cause health concerns. There is a belief that it’s what causing fatty liver disease in children.


Asker Jeukendrup  52:17

Yeah, that’s true. But we’re really talking about overfeeding with fructose here, and so I think eating fructose in moderate amounts, I don’t think we need to, we need to panic about that. But it’s, if we’re talking, overfeeding and definitely overfeeding large, really large amounts, which is how many of these studies are done, then you’re absolutely right. That’s something we should avoid, especially if you’re not exercising.


Trevor Connor  52:45

So, an apple is not going to kill you, but if you’re counting tons of soda, and tons of sports drinks when you’re just sitting around, you might have concerns.


Training the Gut

Asker Jeukendrup  52:53

Yeah, definitely like the rates at which we advise to take it here, that’s not something that of 90 grams of carbohydrate per hour, and then of the 90, 30 grams per hour would be fructose. Those are definitely not amounts that I would recommend for someone who just sits watching TV, even if it’s watching the Tour de France. Yes, so we found really high oxidation rates of 1.75 grams per minute with a mixture of glucose and fructose, it was actually a one-to-one ratio in that. But in that particular study, we gave carbohydrates at 2.4 grams per minute, that’s a very large amount, 144 grams per hour, and certainly not something that I would recommend in a practical setting. We did this study because we wanted to find out, what is the maximum? Because every time we did a study, we saw higher oxidation rates, and so we just wanted to push the system and see where we could take it, 1.75 grams per minute is still the highest value reported in the literature. But in terms of practical amounts, we think 90 grams per hour is practical, it can be tolerated, maybe not by everyone, certainly not the first time, but by most athletes. I think the advice that we always give if we recommend these, these larger amounts of carbohydrate, is that people should train it. It’s not something that you just decide, oh, I have a race next week, I’m gonna just take 90 grams of carbohydrate per hour. I mean, that’s a recipe for disaster, of course. So, you need to, we call a train the gut, unfortunately, the gut is extremely trainable. Just like we can train our muscles, we can train the gut. We don’t have a huge amount of human studies to base this on, but there’s very convincing animal work and some human studies.


Trevor Connor  55:07

I just want to ask you about, that because in your review of all this research, you said that it is very trainable. So, these transporters, or glucose can be increased quite rapidly, like you can see changes in three days, but then towards the end of the review, you said, you still didn’t see rates of glucose oxidization going much over 60 grams per hour.


Asker Jeukendrup  55:31

Yeah, this is based on one human study, where they tried to train the gut over a period of 28 days. They gave extra carbohydrate before, during, and after training, and they compared it to a normal situation where that extra carbohydrate was not provided. So, in both situations, carbohydrate intake was fairly high, but one was even higher, because they took the carbohydrate around the exercise, at the end of that study, after 28 days, they saw that carbohydrate absorption was increased, as evidenced by increased oxidation rates. But yeah, they were not like dramatic changes, but I think they’re very significant changes, because small improvements in oxidation can really make a difference. I also think that’s only one aspect of it. So, they looked at the transport of carbohydrate and the oxidation. But training the gut means also training the stomach, and that is something that your stomach would feel much more comfortable because you’ve trained this several times. There is another human study that shows that effect after just a few days of training. So, if you take a certain amount of fluid, fairly large amount of fluid the first time during exercise you feel bloated and it’s really uncomfortable, but after doing that a few days it’s not uncomfortable anymore, or at least it feels a lot more comfortable than it did before. Then those are really important adaptations as well I think because that feeling of discomfort can actually hold people back taken on fluids, taken on carbohydrates, that they would actually need.


Trevor Connor  57:35

I love the analogy you used in that review where you compared it to professional eaters, people you see eating hotdogs in 10 minutes, and said what was it? They wouldn’t feel bloated?


Asker Jeukendrup  57:50

Oh, I’m not sure they will feel bloated after eating that many dogs, but I think yeah, we see this training the guy does something new, but for those guys that’s what they do. I mean, that’s definitely not news for them that you can train the gut, because they do this preparing for their competitions. They have an on-season and an off-season, and in the off-season, they can’t eat that many burgers or hot dogs, it’s yeah, it’s incredible. So, it’s extremely trainable.


Trevor Connor  58:27

Now obviously, we don’t want to tell our listeners to go eat a bunch of hotdogs on a regular basis.


Chris Case  58:34

I can’t even watch that stuff. It’s so gross to me. It’s unbelievable what they’re shoving in their faces. They’re usually like, isn’t the grand champion of this a small guy from Japan?


Trevor Connor  58:48

They’re not usually big guys.


Chris Case  58:50

Yeah, oh man, that stuff.


Asker Jeukendrup  58:55

The message that people take away from this, that’s what I’m promoting.


Trevor Connor  59:00

Please don’t. The other message I’m going to give, which we’re also not promoting is train your gut with Swedish Fish. I think I was consuming 200 grams of Swedish Fish per hour, and I was tolerating and absorbing all of it, because it’s Swedish Fish


Chris Case  59:19

That is Trevor’s go to food. Maybe you guys could have a whole conversation about that offline sometime, it’s pretty funny.


Trevor Connor  59:27

I actually looked at the sugar ratios in Swedish Fish and it’s completely wrong, but I am a strong believer that once they put it in the form of Swedish Fish and my body absorbs it all.


Chris Case  59:41

Asker, are you familiar with the candy, Nerds?


Asker Jeukendrup  59:44

No, no, no.


Chris Case  59:47

There is an American and I don’t know if it’s only in America, but they are called Nerds, and they’re hard little candies that are packed with you know, sugar, of course. Honestly, I think you really should switch it up, and that should be your go-to ride food is Nerds, because you know, nerd bombs. You are a nerd.


Trevor Connor  1:00:06

Or one of these days I could actually bring along something healthy.


Chris Case  1:00:10

That’s true. That is true.


Trevor Connor  1:00:13

One thing we love to do on the show is use the side interviews to present contrasting opinions. This one may take the cake, both metaphorically and literally. So, after my somewhat embarrassing discussion of Swedish Fish, let’s get a reality check from Colby Pearce. So, I’m sure this is something you’ve had to deal with yourself and had to deal with a lot of athletes. So yeah, what are your thoughts?


Colby Pearce: Opinions on Training the Gut

Colby Pearce  1:00:37

Eat. Real. Food.


Colby Pearce  1:00:43

I think cycling sports in general have a massive double standard, that is astoundingly hypocritical, and it kind of pisses me off a little bit. If I went into a 7/11, and I was just a, quote, normal human, because I’m gonna be noticed, because I’m a superhero because I wear spandex. But if I was a normal person who had you know, job, work in a cubicle, that kind of thing, and I went to 7/11 and came out with a box of cake frosting, and three Gatorades, and a Snickers bar, and a KitKat, you’d be like, why are you eating that crap? But for some reason, it’s acceptable for us to eat these in the middle of a 50-mile ride. I should back up, if you were a conscientious person who believed in whole food diets, you know, eating things that you could find on a forest floor or on a farm, you would be like that is the worst food you can possibly eat, it’s hyper-processed. Bike racers, triathletes, sportsman, all the foods come in plastic wrappers, they’re all hyper- processed, I mean, some less than more, whenever I eat a bar or convenience food, which is what it is, realistically, you got to be honest, it’s a convenience food, I search for the foods that are the least processed. Allies Bars were a great example when they existed, side by line. But I always searched for whole foods, I mean, eat a freaking banana. But for some reason, it’s acceptable for us to eat gels, gels, or cake frosting, let’s be real, like they’re just straight-up sugar, you can put fancy, expensive amino acids in them, and a few other things, but those are cake frosting man, and that is not healthy, it’s not healthy for your teeth, and yes, the insulin responses curd when you’re three hours into a hard bike race, but that doesn’t excuse all the other problems that eating concentrated packets of sugar cause you. Now ultimately, you got to put fuel in the tank to run the drag racer, I get that. But they make things like purple potatoes and basmati rice. Alan published a whole cookbook on delicious real food alternatives you can put in your pocket. So, I think if you’re talking about training the gut to handle things like 74 grams of refined table sugar, then have fun with that. I don’t think that’s I think that’s a fool’s errand to be brutally honest, anyone who thinks that they need to do that for sport is, even if you’re making a lot of money as a professional triathlete or cyclist, kind of doing it wrong, in my opinion, there will be a cost for that, the human body is not a machine, we don’t pour sugar down a hole endlessly and not expect consequences. Now, I sound like a total soapbox preacher here, I was a pro cyclist, air quotes, for years, and I ate lots of gels and lots of bars. So, I get it. Now, just to be clear, like I still race my bike, I still ride my bike quite a bit for someone who, you know, isn’t paid to do it. That’s 8 to 12 hours a week, plus some gym, and occasional big weeks on top of that. Unless I’m literally dying, I will not eat a gel for the rest of my life. I will never have another highly processed energy bar again, period. I don’t put sugar mix in my bottles, even if I’m doing over which is 35 hours riding in one week. I’m just done with that stuff. Higher priority is my health.


Chris Case  1:03:37

What about training the gut to process a larger quantity of calories,


Colby Pearce  1:03:44

Meaning that they’re from healthy source. I mean, I’ll say this, it’s a really simple rule, you go out and you train long and hard, you eat what you’re going to eat on race day, and you try to consume it in the same volume. I’m also really struggling with, and this will be a bit of an unpopular opinion probably in the modern sports world, I really struggle with things like calculators that try to tell you how many grams of carbohydrate you should have per hour, how many liters of fluid, and what solution you should have per hour, man. There’s so many confounding variables just like there are in almost everything.


Trevor Connor  1:04:12

It is also very individual.


Colby Pearce  1:04:13

Everyone’s individual. The gut biome is individual. I mean, you can have two people wearing blood sugar scanner and eating the same thing and get different results. When they’re not exercising, let alone when you add exercise into the equation, then you add temperature, and humidity into the equation how adapted the app that is to that environment, you’ve got a million variables. It’s landing a small aircraft, that’s all it is. Too much speed, to low altitude, you’re going to crash and burn. It’s not rocket science, like again, and these metrics can be useful to instruct the athlete but what are we instructing them to do? We’re always instructing athletes to develop their own internal intuition. You need to know how much food you need. When you wake up in the morning and race and you go, man, I’m a little unusually hungry today, if you’re paying attention, you’ll go, okay, I need a couple five extra bites of oatmeal today or another egg, because it’s a cold race.


Colby Pearce  1:05:00

On the other hand, if you’re like, man, I really am struggling to get this food down, but I know I need something, then maybe you cut your breakfast meal in half and you continue to monitor and then you get a hunger paying 45 minutes before the race, that tells you something. So, you’re always adjusting your speed and altitude of the airplane based on what your body is experiencing, because the body’s a cybernetic organism. It’s a system of systems, it’s very complicated, applying a formula of like 40 grams of carbs per however many minutes of exercise, it’s just no disrespect to anyone who’s done this because I know a lot of scientists geek out on this, but to me, honestly, that’s garbage, useless information, guideline huge and the sky guideline at best, which I can also get someone by saying, don’t eat an entire chocolate cake five minutes before road race or five hot dogs, and also don’t eat 24-hours before. As long as you’re between those two windows, we’re starting to narrow it down from there.


Trevor Connor  1:05:51

You got to find what’s right for you. It sounds like you’re on the same page we’re on of, there’s no such thing as race day food, you don’t on race day suddenly eat differently from how you’ve been eating all the rest of the year.


No Such Thing As Race Day Food

Colby Pearce  1:06:02

I actually have pre-conceived racing menus that are the same, three menu items I pick from and I manufacture, I find a way to pull those together before any important event, no matter what even to this day, even though I’m not really a racer anymore.


Chris Case  1:06:16

No matter where you are, too.


Colby Pearce  1:06:17

No matter where I am, I find those ingredients, and I assemble them, and it’s a recipe. The beauty of that is that for a given amount of food, I can look at the size of the food in the plate without weighing or measuring it and know like this is about how much I should eat, and then I’m monitoring that food intake based on how I feel. If I’m really full or I haven’t been hungry for a day, or really haven’t felt hunger pangs, then I know that I should be conservative, especially if the race is hot, and especially if I’m getting closer to the race, especially if the race is shorter and required more intensity. All those are contributing factors. On the other hand, if I’m doing 110-mile road race or road ride or something, and I’m eating farther away, and it’s going to be a cold day, then I’m going to add a couple more.


Trevor Connor  1:06:55

These are all foods that you eat on days that aren’t race-day as well.


Colby Pearce  1:06:59

Right. Exactly, yeah, yes. Right. They’re not special race meals, they are a little bit more carbohydrate oriented than I would eat on non-race day, particularly a low volume train day, but they’re foods that I would eat, and just to give it away one of them basically basmati rice, a little bit of prosciutto, an egg, a little bit of goat cheese and sea salt. That’s the fundamental, how much of each of those ratios depends on what the total quantity is, and a little bit of olive oil on top, all that changes based on,


Chris Case  1:07:24

I didn’t hear you say cookie in there.


Colby Pearce  1:07:26

No cookies. I’m currently not consuming gluten, just for now.


Chris Case  1:07:31

So, how many cookies do you eat during a group?


Colby Pearce  1:07:34

How many cookies? Yeah, I haven’t counted. Oh, you’re messing with me?


Chris Case  1:07:39



Trevor Connor  1:07:40

He has a cookie obsession.


Trevor Connor  1:07:46

Let’s get back to the show, and talk with Dr. Jeukendrup about strategies he uses to train the gut.


Trevor Connor  1:07:52

Ignoring hot dogs and Swedish Fish, what do you recommend people do to train their gut in a healthier way?


Strategies To Train the Gut

Asker Jeukendrup  1:08:00

Yeah, so this is partly based on research, and partly, we are still guessing. I think in terms of duration, you probably need 10 weeks, and maybe one day a week that is dedicated to training the gut. I think you will see some significant changes over that period. I say one day a week, because I think I don’t think it’s necessary to do much more, or maybe you don’t want to do much more, because, during that session, you would be consuming probably quite a bit of fluid, quite a bit of carbohydrate, and once a week is probably sufficient to do that. I usually say pick the day that looks the most like the race, and then in that particular workout, in that particular training, you just practice your race nutrition. Now, if you use this software I was talking about, Fuel the Core, and it tells you that your carbohydrate intake should be about 80 grams an hour or 60 grams, whatever it is, if it spits out 60 grams, if I take that example, then it probably means that you need to start training at a slightly lower level, and probably 40 or 50 grams is already quite a bit for you. I would do that one day in a week, I would use maybe 40 the first time, 50 the second time, hopefully, it feels a little bit uncomfortable but not too uncomfortable, and then you build up to 60, and if all goes well, then maybe two weeks before the event or three weeks before the event you can actually go up to 70 grams per hour, and a little bit more than you’re actually planning to do in your race because if you can do that 70 grams per hour in training, you can probably do 60 grams per hour in the race, no problem. Of course, if the software would spit out you have to go 90 grams per hour, then yeah, you started maybe at 60, build up to 90, and maybe go 100, or even 110 grams two or three weeks before. Yes, listening to your body a little bit, but also at the same time, just like any training, just pushing the boundaries a little bit. If you’re always comfortable, it’s probably not going to improve, but it needs to be a little bit uncomfortable, or at least borderline. So, I think that’s how I would approach it.


Trevor Connor  1:10:42

Yeah, that was exactly the question I was going to ask you. You’re even calling this training, training by nature isn’t always comfortable. So, when you’re doing this on the group ride, you should feel like not so bloated that you have to fall out of the group ride, but you should feel a little bit bloated, you should feel a little bit uncomfortable, and that’s training your body.


Asker Jeukendrup  1:10:59

That’s right. Yes, yeah.


Trevor Connor  1:11:03

So, the other question I have for you, which is an important one to me, are there any health concerns to this? You said that this endotoxemia doesn’t seem to relate to the symptoms, but there still is evidence that this high carbohydrate consumption can promote some endotoxemia, which isn’t healthy for you. You even showed in some of your studies that high carbohydrate consumption can affect the function of the immune system, it drops your type one cytokine levels, it drops your TNF alpha levels, are there health concerns to this?


Health Concerns

Asker Jeukendrup  1:11:38

My thing generally does, and in terms of the immune function, those changes are usually positive. So generally, carbohydrate, higher carbohydrate intake will help the immune system. So, from that respect, I don’t think there is any health concern, and in terms of bacterial translocation, as I said, I don’t think that really is, is a big issue, and certainly not like related to the carbohydrate intake, if it is, this more related, I think, to the fact that people become extremely hot, extremely dehydrated, or very long periods of extreme exercise. So, I haven’t seen any evidence of negative effects of this, we also have to put this into a little bit of context here, because I talk about large amounts of carbohydrate, because it feels like we’re taking on a lot of carbohydrate. But say we’re taking 90 grams of carbohydrate per hour, that is 360 calories, 360 calories, even for professional cyclists, it’s only one-third of the calories they would be, they would be burning, for the average cyclist, maybe it is 50% of the calories they’re burning in that in that hour. So, we’re not talking about so overeating, it is a fairly large amount of carbohydrate, but it’s not a ridiculous amount. So, we need to keep that context in mind, because I always get the questions of people will again, wait, no, you want, because you’re still burning a lot more than you’re actually ingesting.


Chris Case  1:13:20

When somebody asks you like a specific, what should I eat? You know, you talked about seeking a mixture of maltodextrin and fructose, to get the not to sweets in one dose and then to use the separate transporters, is there a product? Is there specific foods that you highly recommend over others?


What Foods Should You Eat While Training Your Gut?

Asker Jeukendrup  1:13:45

Yeah, it depends, of course, a little bit on what you’re trying to achieve. If this is someone who wants to go up in this sort of 90 grams per hour, then the composition becomes really important. You need to make sure that you have this combination of glucose, and fructose, and maltodextrin, and fructose. But the most important thing related to this question is that you choose a product that you can actually tolerate, the product that you actually like, this is incredibly individual. So, I would never say this product is much better than that product, because it really depends. Some people tolerate one product really well, but not the other, the next person is just as the other way around. So yeah, it’s very difficult, like I can give general guidelines, I would, I would always choose a product that has this maltodextrin fructose ratio of around 2.1, it doesn’t have to be the exact ratio but roughly that especially if you’re taking 90 grams per hour or something similar. I would try and find a product that is not too acidic. A lot of products for reasons of shelf life, but also reasons of tastes, have a very high acidity, and I think that sometimes relates or links to GI problems and some people. I would always look for a little bit of sodium in that drink for a number of reasons, it’s taste, it makes you thirsty, and therefore you just, it’s easier to keep, keep drinking, it helps also with fluid absorption. So, those are really the things that I would be looking for, but there are many products on the market that fit those criteria. So, which product you choose really depends on what you like, and what you can tolerate.


Trevor Connor  1:15:41

Sorry, I’m gonna overrule. Swedish Fish, they trump everything. That’s number one.


Chris Case  1:15:50

Sure. Yeah. How much are they paying you to say that? I thought you didn’t take bribes?


Trevor Connor  1:15:57

This is the worst thing. How many times have I promoted Swedish Fish? They don’t even know I exist.


Chris Case  1:16:03

Well, they should, because we could get a really good sponsorship.


Trevor Connor  1:16:07

Just pure luck.


Trevor Connor  1:16:12

Chris works with Ryan Koehler, the head coach at the University of Colorado Sports medicine Performance Center, on his nutrition strategy for Dirty Kanza, a grueling 13 plus hour event. Ryan frequently works with athletes in training their guts to better handle food during events, he shared some of the strategies with Chris.


Ryan Koehler: Strategies to Training the Gut

Chris Case  1:16:30

I feel like we talked a little bit about it when I talked to you about training for Dirty Kanza, and helping your system get used to loading it with more carbohydrates than it’s used to, stuff like that.


Ryan Kohler  1:16:44

Yeah, that sort of brings in just the metabolic piece, and I guess having that the metabolic component to it, where we tested you, and we knew sort of what you were burning. So, it was, it was easier to suggest, you know, range for you to be in. So, we’ll see that with athletes that come in, where Ironman athletes are pretty typical around Boulder, and actually one athlete earlier this week, or last week I should say, they’re already consuming 400 plus calories an hour on the bike and on the run, and, you know, they’re still experiencing that bonking sensation on the run. So, some of it is, you know, looking at their gut is fairly well-trained to handle a lot of it, but we’re able to identify more, you know, in the pacing side, and what can we do to bring in more carbohydrate at that point, by changing the types of food that they’re eating. So, if we think about treating the gut, we need to get a high amount of carbohydrate in. So, while this athlete was getting, you know, 400 or so calories in, a lot of those calories weren’t necessarily from carbohydrate, because it was you know, there were bars and things like that coming in, so some fats and protein was built in there. So, part of that training gut is getting the athlete used to consuming the right types of foods, and the right types of carbohydrates were that will allow them to get to a higher ingestion rate.


Chris Case  1:18:05

Is that in part, considering the sources of the carbohydrates or?


Ryan Kohler  1:18:12

Yeah, maybe going away from say, a bar that’s rich in fat and protein, which they don’t really need as much about that time, and if we find that they have this high carbohydrate oxidation rate, they just need more carbohydrate coming into the body, we might say, hey, let’s take this bar out, or maybe just do half of it, you know, over this hour, but then let’s find jelly beans, or gummy bears, or something that’s rich in carbohydrate that’s going to allow them to get that intake up there, but then we do have to build in the time component to test it out. I think it’s still a common pitfall for athletes to wait until, you know, three to four weeks before their big event, and then they say, oh, no, I just need to eat more. But we need to do that further out, so yeah, we’ll practice that, and, you know, this time of year is great, where I’ll have athletes go out and do a long ride, so just fuel with this carbohydrate, we’ll say, take this much per hour, and see how your stomach responds to it.


Chris Case  1:19:05

You’re talking about the offseason?


Ryan Kohler  1:19:07

The offseason, yeah.


Chris Case  1:19:08

The offseason is the right time to practice this stuff, not right before your big event.


Ryan Kohler  1:19:14

Right. Yeah.


Chris Case  1:19:15

And what do you mean more specifically, by training the gut, what are you trying to do?


Ryan Kohler  1:19:21

So, just get the body used to processing that amount of food, you know, some athletes have a tendency to either get behind on fueling, and then try to catch up. If they already have sort of, they’re in a dehydrated state, their guts already challenged, and then they put these big bowls of carbohydrate in there, and then that could lead to some GI distress, or if they’re just not consuming enough throughout, then we’ll get a certain outcome from that. So, it’s more just getting the athlete used to saying okay, we are recommending 60 to 70 grams of carbohydrate for you, and if you’re normally taking in half that, then we need to give it time.


Chris Case  1:20:00

It’s a stepwise process, you can’t go from A to B right away, or else there will be some digestive issues most likely. Yeah.


Ryan Kohler  1:20:08

Exactly. Yeah. Then hydration piece, I think has to fall in line with that, because we can throw a lot of food in the gut, but if we’re dehydrated or not handling the hydration piece, then probably still experienced GI distress. So, we have to sort of pair those two together.


Trevor Connor  1:20:22

Let’s get back to the show.


Trevor Connor  1:20:24

I got to jump down a quick tangent, but just something else to bring up or ask you about. How do you feel about a lot of this research coming out now about looking at the microflora balance, because you’re seeing things like, higher lactobacillus, increases SGLT1 expression, you’ve seen benefits of the microflora to improving intestinal integrity, and I know you’re doing some research on green tea powder, correct?


Microflora Balance and Intestinal Integrity

Asker Jeukendrup  1:20:56

Yeah, I am. I mean, I think it’s really early stages, to be honest, for this sort of research, I think it is very clear that it plays a role, but when it comes to manipulating or changing it, it’s a whole different kettle of fish, I think. We don’t really know what to give to change it in our favor, and maybe the same bacteria will also have different effects and different people. So, I think there’s still many, many questions that are unanswered, and at the moment, I don’t think we know enough to say, is this really what we should take? I think where the research probably most advanced is in the sort of the direction of immune function, but even that area is relatively unexplored. So, I’ll find it at the moment, I still find it too difficult to really draw firm conclusions about it and come up with sound advice.


Trevor Connor  1:22:02

It’s a complex subject, like you said, changing it in beneficial ways is tough, and even if you’re taking dramatic levels of probiotics, they show that even when you do change it can reverse back within a matter of days. So, it’s a tough area.


L-Glutamine and GI Distress

Chris Case  1:22:19

What about L-glutamine? Does that have anything? Is it helpful in terms of reducing GI distress?


Asker Jeukendrup  1:22:25

Yeah, L-glutamine is a supplement that has been very popular for a long period of time, for various reasons, has also been linked to GI problems, or helping to prevent it. A bit of the theory is that glutamine is a really good fuel for a GI tract, but I haven’t really seen any evidence that L-glutamine will really reduce GI symptoms. I know people that have tried low dose, high doses of L-glutamine, and they still have the same complaints that they have before. So, I’m not convinced I haven’t seen evidence in the literature either.


Chris Case  1:23:09

So since you’re not familiar, Asker, we like to put our guests on the clock at the end of the show, we all take a turn, we give you 60 seconds to sort of summarizing what we’ve talked about today, give our listeners a very concise takeaway from the episode. So, I’ll put you on the clock. Got one minute, what would you say are the biggest takeaways from this episode?


Asker Jeukendrup Takeaway Message

Asker Jeukendrup  1:23:35

I think some of the biggest takeaways are that GI problems are very common. We don’t know exactly what causes them, but they’re extremely annoying. One of the best ways to deal with them might be to train the gut, at least as far as nutrition goes. We can train the guts by practicing race strategies, taking slightly larger amounts of carbohydrate, larger amounts of fluid than normal, and the gut will just adapt like the muscle will adapt over time. So, and that is a strategy to at least tolerate race nutrition a little bit better. Of course, there are other reasons for GI problems, but they’re very difficult to tackle with nutrition. We also talked about optimizing carbohydrate delivery, we saw that with different durations of events, you need different amounts of carbohydrate, with a longer duration anything over two-and-a-half-hours, we would like to push the carbohydrate intake to 90 grams per hour, but that can only be done really when the carbohydrate that you’re taking is a mixture of glucose and fructose, ideally in the ratio around two to one. If you take that ratio then you don’t saturate glucose, while we still saturate the glucose transporter, but we can actually get more carbohydrate into the body, and studies have shown that increased carbohydrate absorption and oxidation can also have a positive effect on performance.


Chris Case  1:25:16

Very good. Trevor, what would you like to add?


Trevor Connor  1:25:19

I’ve got two. First, Swedish Fish.


Chris Case  1:25:22

I knew that was coming. I knew it, you’re so predictable.


Trevor Connor  1:25:27

That leads to my second point, which is,


Chris Case  1:25:30



Trevor Connor  1:25:31

No, no, you can have Nerds, because you were eating all mine on the weekend.


Chris Case  1:25:36

Yes. Moving on.


Trevor Connor Takeaway Message

Trevor Connor  1:25:38

So, moving on to Swedish Fish leads to an important point of health. We’re talking about performance here. But the more you can do this in healthy ways, the better. You know this is a running joke with me, and I love my Swedish Fish, but the truth of the matter is, there are a lot healthier ways to accomplish the same thing.


Chris Case Takeaway Message

Chris Case  1:25:58

I guess this is something maybe Asker has already touched upon a couple of times, but I’d like to reiterate just sort of practicing this stuff well before race day, not in race day, but getting to know what works for you, what doesn’t work for you, what ratios work for you, what products work for you, well ahead of time, and not to experiment in the two or three days leading up to a race, certainly not within a race. I think the word that you used was very, very appropriate, these things are annoying, but you can find ways. It’s difficult. Individuals bring their own problems, and it’s a lot of trial and error sometimes to figure it out, but you just have to be somewhat methodical about it and patient and persistent. So yeah, that’s what I would end with.


Trevor Connor  1:27:00

That was another episode of Fast Talk. As always, we love your feedback. Email us at Subscribe to Fast Talk in iTunes, Stitcher, Spotify, SoundCloud, and Google Play. Be sure to leave us a rating and a comment. While you’re there, check out our sister podcasts, the VeloNews podcast which covers news about the week in cycling. Become a fan of Fast Talk on Facebook at and on Twitter at Fast talk is a joint production between VeloNews and Connor Coaching. The thoughts and opinions expressed on Fast Talk are those of the individual. For Dr. Asker Jeukendrup, Katie Compton, Colby Pearce, Ryan Kohler, and Chris Case. I’m Trevor Connor. Thanks for listening.