How to Avoid Stomach Ache Before and During a Race

October 9, 2017 , , ,

Autumn is marathon season for many runners. After months of training, there will be just one step left before the gun fires: The line-up in front of the many (we hope) porta-loos. Did you know that 30 to 50% of endurance athletes suffer from gastro-intestinal symptoms? Stress combined with maximum effort often make the symptoms worse on competition day! What can you do to avoid being bothered by your intestines during your race or sports event?


Recently, researchers have looked into the question and discovered that a low-FODMAP* diet could be a possible solution. FODMAP means: Fermentable Oligosaccharides, Disaccharides, Monosaccharides and Polyols. In simple terms, those are sugars that the small intestine cannot absorb, which ferment in the colon and produce gas and other gastro-intestinal symptoms (diarrhea, bloating, cramps, etc.) More precisely, those sugars are fructans, lactose, fructose, sorbitol, mannitol and some found in certain legumes.

During the study in question, 11 runners were divided into two groups and followed either a low-FODMAP diet or a high-FODMAP diet, for 6 days. Of course, participants didn’t know which diet they were assigned to. We asked them to describe their symptoms each day, including during training. The result was that runners in the low-FODMAP group experienced significantly fewer gastro-intestinal symptoms during the day (diarrhea, flatulence and urgent need to defecate) compared to runners who ate a high-FODMAP diet. However, symptoms during training were no different between the two groups. Therefore, following a low-FODMAP diet could help reduce gastro-intestinal symptoms before a race or training.

But beware! Following a low-FODMAP diet all the time is not recommended! In fact, it’s a very restrictive diet that is not designed to be followed long term because it can cause nutritional deficiencies. For example, if we eliminate legumes and wheat, we eliminate important sources of prebiotics, which can cause changes to the intestinal flora and weaken the immune system. However, athletes who usually experience gastro-intestinal trouble could find it useful to follow a low-FODMAP diet a few days before a major event, for example three days before. Or, even better, they could do tests beforehand to identify which FODMAPs cause the problem, since it varies from one person to the another. For instance, it’s possible that a runner may only have an intolerance to lactose, whereas another may not tolerate garlic, onions, mangos, avocados and honey.

Finally, FODMAPS don’t cause gastro-intestinal symptoms for everyone. Here are a few other tips to help you avoid having to run to the toilet before and during your sports event:

  • Eat a complete meal at least 3 hours before the event.
  • Avoid eating foods rich in protein or fats in the 3 hours preceding the event.
  • Choose a drink that isn’t too high in glucose (ideally 5 to 7%)
  • Avoid drinking too much, but stay hydrated.
  • Don’t try foods or supplements you aren’t used to eating before an important event.

For other tips and examples of low-FODMAP choices, see our article FODMAPs, Endurance Sports, and Runner’s Diarrhea.

SOSCuisine: Low FODMAP Meal Plans

*FODMAPs are fermentable carbohydrates that are partly responsible for causing symptoms in people with irritable bowel syndrome (IBS). For more info, read this article.



Kathryn Adel
Kathryn completed degrees in kinesiology and nutrition, as well as a Masters in Sports Nutrition. She is a member of OPDQ and of the Academy of Nutrition and Dietetics. She ran track and cross-country at a national level. Kathryn specializes in sports nutrition, weight loss, diabetes, as well as heart and gastrointestinal health. Kathryn is experienced with the low FODMAP diet and she completed the Monash University low FODMAP dietitian's training.

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