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Runner's Diarrhea Can Occur with Athletes

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It’s one of those ironies of life: You are doing something healthy and you still get sick. In this case, the step toward better health is endurance running. And the ailment is diarrhea, occasionally a side effect of what’s happening to your digestive system as you log the miles. Luckily, though, you can usually recover within a day or two.

If you’re wondering how common it is, though, browse the blogs and online forums for active people and habitual runners and you’ll see that “runner’s diarrhea” is not taken lightly -- even for those humorously referring to it as “runner’s trots.” In fact, those engaged in the conversation are seeking answers to a problem that can plague them while training, as well during and after a big race.

Why does it happen? The answers might have to do with blood circulation, any food and drink you have consumed, or just how accustomed your body is to the hard work of endurance running. Experts theorize that during intense exercise, oxygen-rich blood rushes to where it’s needed -- in the legs, heart and lungs -- sometimes shortchanging the intestines. As explained in a July 7, 2011, health story in the Bend (Oregon) Bulletin, the gut becomes irritated, and the jarring movement in the act of running doesn’t help the situation.

Another cause might have to do with carbohydrate-loading. Whether you are consuming naturally high-carb foods or energy gels and bars, you might be straining your digestive system, which wants to quickly dilute the carbs. The result can be watery diarrhea.

Other considerations include dehydration, hormonal changes and a bacterial imbalance, according to the article.

An article by the Mayo Clinic offers a number of suggestions for preventing runner’s diarrhea, mostly having to do with limiting certain food and drink in the days and hours leading up to a long-distance race. For instance, at least one day before running, limit or avoid high-fiber foods, the site said. Also, for three to six hours before running, limit or avoid caffeine and high-fat foods.

Writing for Runner’s World, Dr. Linda White had some helpful strategies, such as consuming bananas, unsweetened oatmeal and other low-fiber carbohydrates before a race. She also suggested gradual boosts to your exercise level, say, 10 percent each week, to allow your muscles to learn how to use oxygen more efficiently and thus ensuring enough blood flow to the intestines.

Be sure to report continued cramps and diarrhea, especially bloody diarrhea, to your healthcare practitioner. Other digestive concerns for runners include acid reflux, vomiting and nausea, which also should be reported.


Aurand, Anne. “Intestinal troubles: Endurance athletes have high rate of gastrointestinal problems.” The (Bend, Ore.) Bulletin. bendbulletin.com. Web. 29 Aug. 2011. http://www.bendbulletin.com/article/20110707/NEWS0107/307079997/

“Runner’s diarrhea: How can I prevent it?” Mayo Clinic. mayoclinic.com. Web. 29 Aug. 2011. http://www.mayoclinic.com/health/runners-diarrhea/AN00376

White, Linda, M.D. “Does running give you an upset stomach? Get some relief.” Runner’s World. active.com. Web. 29 Aug. 2011. http://www.active.com/running/Articles/Does_running_give_you_an_upset_stomach__Get_some_relief.htm

Reviewed August 29, 2011
by Michele Blacksberg R.N.
Edited by Jody Smith

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We value and respect our HERWriters' experiences, but everyone is different. Many of our writers are speaking from personal experience, and what's worked for them may not work for you. Their articles are not a substitute for medical advice, although we hope you can gain knowledge from their insight.