Has any athlete not experience gastrointestinal (GI) symptoms, such as nausea, upset stomach, diarrhea and bloating, during exercise. Unfortunately, it’s all too common, especially during strenuous exercise like running. Through experience, most of us know how detrimental GI disturbances are on exercise performance. GI disturbances triggered by exercise can be due to changes in blood flow from the gut to working muscles and also by increased activation of the sympathetic nervous system. Athletes may also be more susceptible to dietary triggers because of the stress placed on the gut during exercise leading to gut injury.
There is no shortage of strategies to prevent GI issues such as avoiding foods high in fibre and fat pre-exercise or training the gut to increase carbohydrate tolerance. One common strategy utilized by athletes is eliminating gluten from the diet after a self-diagnosis of non-celiac gluten sensitivity or gluten intolerance. However, research shows that following a gluten free diet does not have a positive benefit on performance, gastrointestinal health or wellbeing. Interestingly, the reduced GI symptoms that some athletes find when eliminating gluten containing products could be from the inadvertent elimination of FODMAPs from their diet, rather than gluten. FODMAPs stands for: fermentable, oligo-, di-, monosaccharides, and polyols. See the table below for foods high in various FODMAPs.
| FODMAP types: | Examples of food high in this FODMAP: |
| Fructans | Wheat, rye, barley, garlic, leek, onion, lentils, chickpeas, legumes, cashews, pistachios |
| Galacto- oligosaccharides | Lentils, chickpeas, soybeans, kidney beans |
| Lactose | Milk, yogurt, ice cream, custard, dairy desserts |
| Excess fructose | Apples, pears, mangoes, watermelon, high fructose corn syrup, honey |
| Polyols | Nectarines, peaches, plums, cauliflower, mushrooms, sugar snap peas, chewing gum |
While gluten is a protein, FODMAPs are types of carbohydrates. For some people, FODMAPs are poorly digested. When the poorly digested FODMAPs enter the intestine, it can lead to GI symptoms such as bloating, abdominal pain, gas and alterations in bowel movements. Following a low FODMAP diet is considered one of the first-line treatments for reducing GI symptoms for those with Irritable Bowel Syndrome. However, there is now research showing reduced GI symptoms during exercise when a low FODMAP diet is followed by athletes. There are two strategies that can be used:
-Long-term low FODMAP diet: a low FODMAP diet is implemented, followed by a re-challenge stage of foods high in FODMAP to determine individual tolerance levels
-Short-term low FODMAP diet: strict low FODMAP diet for a few days (24 hrs to 3 days) in the days leading up to an important race
A low FODMAP diet is not meant to be followed long term as this can have negative impacts on health and cause unnecessary dietary restrictions. Even for those taking the long-term low FODMAP diet, foods containing FODMAPs are eventually re-introduced. Before starting a low FODMAP diet to help manage GI symptoms, traditional nutrition strategies to reduce GI symptoms should first be tried. Other potential causes of GI symptoms, such as Crohn’s, Ulcerative Colitis or Celiac disease, should also be ruled out. As the low FODMAP diet is extensive and highly restrictive, it should be followed with the help of a dietitian to ensure that it is warranted and appropriately followed.
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