Leaky gut in endurance athletes

Hi all, lately I’ve been reading more about leaky gut syndrome in endurance athletes. This means temporary intestinal permeability directly caused by a hard-effort endurance training session or race, as opposed to a chronic condition unrelated to endurance exercise. This in turn can cause temporary GI problems, but it seems that it also may cause more serious health conditions over decades of riding. This has implications for what we can do to protect our gut before, during and after high intensity rides. Because no we’re not gonna stop riding! But maybe we can take protective measures.

I would love for FastTalkLabs to have a podcast on this, with expert interviews. I’m also wondering if there are any experts who can post here on this topic. Here is one study I read, to get things started: Is There an Exercise-Intensity Threshold Capable of Avoiding the Leaky Gut?

Thanks a lot,

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I 2nd this suggestion by @northk being a valid topic. Considering my wife is an FNTP (Functional Nutritional Therapy Practitioner) we’ve had this discussion countless times.

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Thanks - I’ve added it to the “requested ideas” chart!

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Hi North,

This one caught my eye so I did some reading on it, including the paper you cited.

To reiterate for all, leaky gut syndrome is a condition where the lining of the gut becomes more permeable, allowing bacteria, toxins, and other substances to leak into the bloodstream. In athletes, this can be caused by intense exercise, prolonged exertion, and other factors such as stress and poor nutrition. The paper you cite talks about both a blood flow issue (blood is diverted away from the gut circulation so that it can be used by muscles, and potentially skin if its hot) and a neural issue - i.e., if you’re stressed, or above threshold, the sympathetic fight or flight system is activated meaning reduced neural function in the GI system.

When the gut becomes leaky, it can lead to inflammation and immune system activation, which can impair athletic performance and recovery. In addition, the increased absorption of toxins from your gut and other harmful substances can contribute to various health problems.

Symptoms of leaky gut syndrome include digestive issues such as bloating, gas, and diarrhea, as well as fatigue, joint pain, and skin problems. Treatment may involve dietary changes to reduce inflammation, such as avoiding processed foods and increasing intake of anti-inflammatory foods.

My 2c is that the key factors you should focus on if this is plaguing you are 1) check your diet - eat clean, 2) look at your food timing around your riding - personally I prefer training with little in my system post morning BM, and 3) train consistently, progressively and in a polarized fashion with a focus on raising your fat max or threshold/FTP. The bigger you build your base (fat max), the less stressful that HIIT work will be on you, and the less effect that both leaky gut factors (neuroendocrine and circulatory) will impact you.

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@PaulLaursen thanks for your reply. I think the situation and solution is more complicated than simply eating a clean diet, meal timing, and training consistently. I suspect most of us already do those things, yet I also suspect this issue affects (or will affect) a lot of cyclists.

We already know that a lot of cyclists experience GI system problems during or after heavy efforts. But, are there cumulative effects over time, and what are those effects? Probably most riders don’t even know it until body systems start having trouble from the leaky gut syndrome after decades of hard riding. I think this is the case for me, and probably others too.

Also, the statement about HIIT being less stressful with a solid base of training does not make sense to me. HIIT is always stressful if you are doing it right.

I am hoping more research can be found by this group, and that FastTalk will do a deep dive. Specifically, I am wondering if there has been any research measuring leaky gut levels directly before and after hard workouts, and the effects of trying different interventions to protect the gut during these efforts.

The best parts of Dr. Allen Lim and Biju Thomas two books, The Feed Zone Cookbook and Feed Zone Portables were their detours into the gut.

Dr. Lim really breaks down exactly how leaky gut happens and criticizes highly concentrated sports drinks, gels, bars, gummies, etc. It’s eye-opening how these sports nutrition products are like a time bomb if you don’t consume them with enough water – nevermind if you are already in a dehydrated state.

Dave Trendler
Fast Talk Labs

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In this paper I was part of with Dr Seiler & colleagues, we observed the carb and fat oxidation during HIIT in a group of recreational runners and a group of very well trained runners. Massively different training volumes (2-4 v 6-10 training sessions per week). Little base v big base. What we found interesting was that everything across the board (carb ox, lactate, RPE) was the same between the groups. What separated the groups was their fat oxidation rate during HIIT (highest in well trained). This tended to explain the better HIIT performance of the well trained group. While this doesn’t definitively say that stress of and recovery from HIIT will be better, there is theory and anecdote to suggest that they are coupled.

So, is HIIT always stressful if you’re doing it right? I’m not so sure it is. I am aware of the overwhelmingly dominant cross-fit promoted ‘no-pain, no-gain’ philosophy. However this was not the original purpose of HIIT used by endurance coaches optimizing training for their Olympic runners in the early 1900’s. Their aim was to always ensure athletes leave sessions like they could do one or two more intervals. You always want to leave a session so that it doesn’t damage tomorrow’s session. That’s because training consistency wins out as the most important factor over any single monster session (Chapter 1; ref).

Stephen Seiler also makes this point very clear during a talk we had on this subject last year.

Bottom line for me: stress is clearly a contributor to leaky gut and you can get stress in many different ways (nutrition, environment, and HIIT done to exhaustion, amongst others). I think if you can lower the stress on your body using any of those methods (or multiple methods) you might lower the leaky gut symptoms.