Runner’s Diarrhea & Other Digestive Issues During Exercise
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CTV News LogoIt can be an embarrassing problem that few people like to talk about, but gastrointestinal issues are a very common problem for runners, triathletes, and gym enthusiasts.  The good news is there are a few ways to help prevent runner’s diarrhea, cramping, and other digestive symptoms during exercise.

Why are reflux, cramping and diarrhea common during exercise?

marathonDuring exercise there is a decrease in pressure of the lower-esophageal sphincter (valve that connects the esophagus which is the long tube between the mouth and the stomach).  This may mean you are more likely to experience reflux or heartburn if you are sensitive to this or have not chosen your pre-workout meal properly.

Although physical activity can slow digestion of food in the small intestine, it can speed the transit time of fecal contents in the colon. The result can be the urge to have a bowel movement during exercise or after high intensity exercise.

Diarrhea and cramping may also occur because there is a reduction in blood flow to the arteries that supply the small and large intestine (since blood is being shunted to the working muscles).

Who is most likely to suffer from digestive issues and runners diarrhea?

Very high intensity exercise sessions or endurance sports (such as marathon runners or triathletes) are more likely to experience cramping, reflux, diarrhea, or even vomiting.  Race days and competitions often increase stress and can lead to more digestive issues than regular low stress training days.

If you have IBS (irritable bowel syndrome), GERD (gastro esophageal reflux disease) or other digestive issues, you may be more susceptible to gastrointestinal issues during or after exercise.

If you have consumed food too soon prior to exercise, or taken in too much fibre, fat, caffeine, or acidic foods, you are more likely to experience symptoms.  Taking in a large amount of sugary foods without proper hydration can also lead to issues.

What are the nutrition recommendations to prevent runner’s diarrhea and other digestive issues during exercise?

1.  Familiar and tested

Since there is a wide range of tolerance of foods and susceptibility to digestive issues, the biggest things to keep in mind is testing the timing, type, and frequency of food and beverage that ideally works for you.  Finding out what works for you is extremely important if you will be competing in a race or competition so you won’t rely on the organizer of the event and can supply what works uniquely best for you.

2.  Timing

If you have had chronic issues with digestive issues before, high intensity exercise solid food should be avoided 3 hours prior to exercise.  Some athletes may be able to handle food 1-3 hours before activity and in this case be sure to make the meals mostly carbohydrate rich since they are quickest to digest.

3.  Liquid vs solid

Often liquid foods are easier to manage than solid foods, so experiment with smoothies or sport drinks prior to exercise to see if this is easier to manage than chewable foods.  Competitive athletes suffering frequent and severe diarrhea and urges to have bowel movements during exercise can benefit from low fibre liquid meals during the last day before competition.

4.  Water & carbohydrate considerations

If exercise is less than one hour in duration, avoid use of sugary sport drinks and choose water.  Staying hydrated is key since dehydration causes reduced blood flow which in turns causes diarrhea. If exercise is intense and longer than 1-1.5 hours than fluids and taking in some carbohydrates are important.  In this case be sure to select a sport drink mixed to direction (mixing sports drinks too strong or taking in too much carbohydrate/sugar from foods can cause diarrhea).

5.  Foods to avoid

Foods too high in fibre, fat, and protein can slow digestion and cause digestive issues.  Keep meals before exercise, and during mostly carbohydrate based to fuel the muscles and since they are quickest to digest.  Avoid caffeine before exercise as it increases transit time and has a laxative effect.

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