Diarrhea in Athletes – Stopping the Runs!


Most athletes have been caught out at some stage during training or racing. That sudden urge to get to the toilet, that feeling that it’s too late to get there, or that sudden dash behind the nearest bush or fence! While little research has been done on this unpleasant topic, it may surprsie you that between 30 and 50% of athletes, especially runners, have had the runs! Here is a recent review of the issue that examines the triggers to diarrhea and the tips to managing it.

The Triggers

Research has consistently shown that the following factors contribute to exercise-induced diarrhea:

  1. Running and jumping movements that jostle the intestines.
  2. High concentrations of carbohydrate (eg sports gels, lollies, sportsdrinks, softdrinks, high GI foods) that can cause water to be sucked into the intestine.
  3. Dehydration with body weight loass greater than 4%.
  4. Anxiety and stress so commonly seen before major events.
  5. Inexperience and lack of knowledge about pre-exercise eating.
  6. Being female, especially during the mentrual period.
  7. Having mild food intolerances (eg lactose intolerance) that may be dormant at rest but get aggravated during exercise when the gut becomes more sensitive.
  8. Having pre-existing bowel problems such as coeliac disease or Irritable Bowel Syndrome – an estimated 10-20% of people have this!

Common pre-exercise food triggers include:

Foods take between 1 and 3 days to m ove through the gut from top (mouth) to bottom. Thus, athletes need to experiment and learn what works for them in terms of pre-eevent food intake. Here is what research has found to date are the common triggers for gut upsets:

  1. Fiber. High fibre foods increase transit time through the gut. Athletes who experience diarrhea should cut back on these foods leading into events.
  2. Sorbitol is a type of sugar found in sugar-free gum, lollies, and breath mints. It can trigger diarrhea in some people.
  3. Coffee, tea and other warm drinks. Hot fluids can stimulate gut movements while caffeine itself can have a laxative effect.
  4. Fatty foods such as burgers, chips, spare ribs and fried greasy food can cause issues in athletes who have trouble digesting fatty foods.
  5. Spicy foods can cause issues in athletes who have trouble with these meals at normal times (eg curries, mexican etc).
  6. Alcohol in large amounts.
  7. Vitamin C in large doses.

So what?

Athletes with diarrhea issues should conduct experiments on themselves by trying any of the normal triggers they think might be the issue. For example, if you think a cereal meal for breakfast might be the culprit, elimiante it from the diet for a few days and see what it does to your bowel movements. Alternatively, consume a larger amount of the suspect food and observe any changes.

Other tips suggested to help manage diarrhea include:

  • Drink a warm drink (warm water, coffe or tea) when you wake up to stimulate a bowel movement. Allow time to sit on the toilet before racing or training.
  • Exercise lightly before training hard and plan your route to be near a toilet (or carry toilet paper!)
  • Experiment training at different times of the day.
  • Experiment with pre-exercise foods to see which are safe and which aren’t.
  • Choose pre-exercise foods that tend to be more constipating such as white bread, bagels, white rice or white pasta.
  • Train near toilets or plan a route near public toilets, service stations, fast food joints etc.
  • Chat with your family doctor about ther possibility of Coeliac Disease or Irritable Bowel Syndrome.
  • Antidiarrhea Medication. When all else fails, ask your family doctor about medications such as Imodium or Lomotil and take them an hour before the major event.

Source: Clark, N. (2012). Recognizing and managing exercise-associated diarrhea. ACSM’s Health and Fitness Journal, 16(3): 22-26.