A bane of many recreational runners is gastrointestinal upset, not unlike irritable bowel syndrome (IBS) during their run. Being hit with a bout of stomach cramps and bloating during exercise is not conducive to performing well, not to mention the general unpleasantness.

Looking at the research into diet and IBS more generally, there is a lot of interest in the role of a low-FODMAP diet.

FODMAP is an acronym for fermentable oligosaccharides, disaccharides, monosaccharides, and polyols and includes carbohydrates such as lactose, fructose, fructans (long chains of fructose molecules) and sugar alcohols.

FODMAPs are found in many foods including wheat, milk, pears, plums, onions, garlic, and legumes.

FODMAPs can be poorly absorbed in some people, leading to their accumulation in the small intestine and passing into the large intestine.

Once there, they can draw more water into the bowel, increasing the chance of diarrhoea as well as gas production from their fermentation by colonic bacteria. These effects of FODMAPs in the bowel explain many of the symptoms reported in IBS.

Could a low-FODMAP diet help ease gastrointestinal problems in runners?

This was the question asked by University of Cambridge scientists. The study involved a group of 16 healthy recreational exercisers.

Each person followed a specially designed diet that was either high or low in FODMAPs for one week and then after a week back on their regular diet, switched to the alternative diet for the following week.

Surveys to assess the degree of IBS-like symptoms were filled out by each person at the beginning and end of each diet period.

Recreational runners who switch to a special diet that cuts out potential problem foods saw improvements in gastrointestinal problems.

When following a low-FODMAP diet, a clear benefit was seen with a 69 per cent drop in gut symptoms. What’s more, the symptom improvement meant that the volunteers were able to exercise more frequently and at a higher intensity.

A low FODMAP diet was likely improving symptoms of pain and bloating by reducing the volume of water being drawn into gut by an osmotic effect and providing less fermentable carbohydrates for colonic bacteria to produce gas.

Implications

Research into the benefits of a low FODMAP diet in offering relief from IBS continues to grow. For recreational runners who frequently experience gut problems, then trialing a low FODMAP diet may offer some benefit.

However, it is important to seek appropriate advice on implementing this diet to help minimise unnecessary reductions in total energy and carbohydrate intake that may affect the nutritional quality of the diet.

Last Reviewed: 10/03/2020

© Norman Swan Medical Communications.



References

For reference: Wiffin M et al. Effect of a short-term low fermentable oligosaccharide, disaccharide, monosaccharide and polyol (FODMAP) diet on exercise-related gastrointestinal symptoms. Journal of the International Society of Sports Nutrition Epub online 15 January 2019 doi: 10.1186/s12970-019-0268-9.