How to Prevent Digestive Issues During Exercise

February 19, 2019 , , ,

Did you know that more than 50% of endurance athletes suffer from gastrointestinal issues during an endurance event such as a marathon or a triathlon? Reported symptoms include nausea, vomiting, gas, bloating, stomach pain, an urge to defecate, and diarrhea. Here are three aspects to consider to avoid gastrointestinal issues during exercise!

When we begin to exercise, our body undergoes changes to adapt to the stress induced by the effort, which can disrupt the digestive system. When starting exercise, there is an increase in blood flow to the muscles to provide them with the oxygen and nutrients that they need during physical effort. As a result, there is less oxygen available to the gastrointestinal system, which causes damage and inflammation to the intestines. There is also a stimulation of the sympathetic nervous system, which reduces the rate of digestion and can thus affect the transport of nutrients. This means that if you consume carbohydrates or other nutrients before or during exercise, they may be poorly absorbed. Malabsorption of protein and carbohydrate can also occur after exercise when consuming a recovery beverage or snack.

Several factors may exacerbate digestive symptoms such as: the intensity, duration and type of effort, the level of fitness of an individual, the tolerance of the individual to different foods, types and amount of supplements and beverages consumed during exercise, training in the heat and heat acclimation, as well as taking anti-inflammatory drugs. Fortunately, it is possible to avoid digestive symptoms during exercise. Here are three aspects to consider!

1) Begin your exercise well hydrated, and avoid dehydration or overhydration

When digestive discomfort occurs during exercise, there is a tendency to associate these symptoms with foods, beverages or supplements that have been consumed. However, it may be simply your level of hydration that is responsible! Indeed, dehydration causes a decrease in blood volume, which reduces blood flow to the intestines and delays digestion. Dehydration also decreases the body’s ability to regulate its temperature, thereby increasing body temperature. On the other hand, drinking too much can also cause digestive issues. Studies show that a proper level of hydration before and during exercise can reduce the frequency of digestive symptoms and reduce the malabsorption of nutrients contained in the pre-workout meal.

The American College of Sports Medicine recommends drinking 5 to 10 ml of fluid per kilogram of body weight two to four hours before exercise to optimize hydration levels. Light colored urine (such as lemonade) is a good indicator of adequate hydration levels. However, it should be noted that taking certain vitamins can make the urine darker. During physical exercise, it is advisable to drink regularly, according to one’s thirst. Finally, consuming cold beverages when exercising in the heat can also help reduce digestive symptoms.

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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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