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Reasons for Athlete Gut Troubles Revealed

Gazelle Nutrition Lab / Blog  / Reasons for Athlete Gut Troubles Revealed

Reasons for Athlete Gut Troubles Revealed

Stomach trouble during exercise got you down? You aren’t alone. Athlete gut trouble is common. Studies suggest that on average, between 30 to 50% of all athletes experience some form of gastrointestinal (GI) distress.

Which Athletes Have Gut Trouble?

Gender, age, environmental conditions, and sport-type all factor into how often gut troubles turn up. In long-distance runners, for example, 30-90% report stomach issues, while in ultra-endurance events, 93% of long-distance triathletes demonstrate symptoms. Symptoms include nausea, vomiting, abdominal cramping, diarrhea, and even blood loss in bowel movements.

Gut issues are more common in novice athletes but even the pros can’t avoid them. Des Linden, the 2018 Boston Marathon Champion, reportedly said of this year’s Boston finish “Honestly, I was just trying not to vomit”. Even soccer superstar Lionel Messi was plagued with vomiting before his matches before he reportedly changed his diet to include a healthier balance of foods.

In this blog, I look at why athletes suffer from gut issues. Check and some possible solutions to your gut ailments.


Athlete Gut Trouble: Possible Causes

The reason athletes experience gut trouble is not fully understood. Even so, a look at gut biology can give us some clues about causes.

Exercise affects how your gut works. It changes how you absorb food and fluid. Exercise affects gut motility, or how quickly food moves through your digestive system. Finally, it can impact the function of the barrier between your gut and body, known as your intestinal barrier.

But, exercise affects everyone differently.  There are might big differences in how your GI system reacts to exercise compared with your training buddy. What works for one person will not necessarily work for the next person.

Changes in Circulation

You need good blood circulation in your gut, or splanchnic perfusion, to absorb nutrients well.  During exercise, your body sends more blood to the tissues that need it most- like your muscles, skin, heart and lungs- and less to your GI system. For some people, the resulting effects are mild. For others, exercise, especially intense exercise, reduces gut blood circulation a lot. These changes in circulation can cause symptoms like nausea, vomiting, abdominal pain, and diarrhea.

Exercise draws blood circulation away from the gut

Changes in Movement

Gut movement, or motility, also plays a role in GI symptoms during exercise. When we swallow food it is pushed into our esophagus, the tube that connects our mouth with our stomach. The esophagus moves food to our stomach using waves of muscle contraction, called peristalsis. Exercise can change how our esophagus moves, or the muscle tone where our esophagus meets our stomach. These changes may result in belching, reflux, nausea, and vomiting.

Lower down, physical activity can affect how readily food and fluids empty from our stomach into our GI tract for digestion and absorption. Studies suggest that both intense exercise and hypohydration (i.e. not drinking enough) affect our stomach emptying and can contribute to gut symptoms.

Dehydration can cause but upset

Changes in Permeability

Finally, there is research that suggests intense and prolonged exercise may make our GI tract more permeable. Some researchers have found that the gut may become more permeable after running a marathon, and others have suggested that gut permeability may cause symptoms in runners.

Distance runners are susceptible to changes in gut function


Not everything is known about why we suffer from gut issues when we exercise. We do know that gut blood circulation, movement, and permeability all play a role. Figure out which factors play a role for you- everyone is individual.

Now that you have a sense of why you’ve been suffering, check out my next blog for how to solve your gut problems.


Nutrition planning is integral to achieving your optimal athletic performance. Gazelle Nutrition Lab delivers one-on-one or group nutrition counselling and consulting to both recreational and high-performance athletes. In addition, the Gazelle Blog is a free resource for healthy recipes and health tips. Have questions? We’d love to hear from you! Get in touch!


Additional Sources

Bytmoski JR. Fueling for performance. Sports Health. 2018;10(1):47-53.

De Oliveira EP, Burini RC. The impact of physical exercise on the gastrointestinal tract. Curr Opin Clin Nutr Metab Care. 2009;12:533–538.

De Oliveira et al., Gastrointestinal complaints during exercise: prevalence, etiology, and nutritional recommendations. Sports Med. 2014(Suppl 1):79-85.

Lambert GP et al. Absorption from different intestinal segments during exercise. J Appl Physiol. 1997;83:204-212.

Lambert GP, Lang J, Bull A, et al. Fluid restriction during running increases GI permeability. Int J Sports Med. 2008; 29: 194–8.

Moses FM. The effect of exercise on the gastrointestinal tract. Sports Med. 1990;9:159–172.

Pfeiffer B, Stellingwerff T, Hodgson AB, et al. Nutritional intake and gastrointestinal problems during competitive endurance events. Med Sci Sports Exerc. 2012;44:344–351.

Rao KA et al. Objective evaluation of small bowel and colonic transit time using pH telemetry in athletes with gastrointestinal symptoms. Br J Sports Med 2004;38:482-487.

Ryan AJ et al. Effect of hypohydration on gastric emptying and intestinal absorption during exercise. J Appl Physiol. 1998;84:1581-1588.

ter Steege RW, Van der Palen J, Kolkman JJ. Prevalence of gastrointestinal complaints in runners competing in a long-distance run: an internet-based observational study in 1281 subjects. Scand J Gastroenterol. 2008;43:1477–1482.





Ashley Leone

Ashley is a Sports Dietitian and Owner of Gazelle Nutrition Lab. Ashley provides nutrition advice and plans to athletes and everyday active people alike. Her goal is to help fuel your inner athlete and put good sense back into eating. Ashley is an enthusiastic and knowledgeable nutrition specialist with over 20 years of experience.

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