What to eat to avoid the runner's trots (aka exercise-induced gastrointestinal syndrome)


Have you ever experienced gastrointestinal discomfort while running or training? You are not alone!


Gastrointestinal (GI) discomfort is widely common among endurance athletes and long-distance runners. It has been observed that between 30-50% of endurance athletes, especially those training at a high intensity, have reported gut issues and a variety of symptoms. The problem is that GI symptoms can prevent many athletes from training at the maximum of their ability and achieving the expected results. Furthermore, the chance to withdraw from the race because of unbearable discomforts is very high.



What are the common symptoms?

The reported symptoms may vary from mild (light gas) to severe and can be classified into upper GI tract (bloating, nausea, vomiting) or lower GI tract ( flatulence, diarrhoea, cramping). There are different factors that influence the severity and prevalence of GI symptoms: the type of physical activity, the athlete’s adaptation to that particular activity and the environmental conditions. Among the common symptoms reported by athletes we found:


- nausea

- reflux or heartburn

- bloating

- flatulence

- diarrhoea

- vomiting

- stomach pain

- cramps


Those who experience these symptoms are likely to suffer from a syndrome called “exercise-induced gastrointestinal syndrome”, which usually occurs during intense activity that lasts more than 2 hours and is undertaken under hot and humid environmental conditions. The severity of gut symptoms might be influenced by inadequate fluid intake and food intake timing before, during or after exercising.


But what are the most common causes of GI discomfort?

Unfortunately, the exact cause is still unknown. However, there are multiple factors that are likely to trigger those gastrointestinal uncomfortable symptoms. One of the main causes is that during training, especially when running, the blood is diverted from the stomach and intestine to the working muscles, for example, your legs and arms. As a result of the reduced blood and oxygen supply to the GI tract, the gut lining is more prone to injury and loses its defences - damage and inflammation will occur with the onset of GI symptoms.

Moreover, running generates vibration around the abdominal wall and the pounding of the GI tract organs, which lead to the feeling of needing the toilet. Finally, another factor that must be considered is the athletes’ posture: for example, cyclists or rowers may experience more gut symptoms than other athletes due to the compression of the colon and the flexed posture of the abdomen while they train.





What nutritional strategies can you adopt to reduce the discomfort?

There are a variety of nutritional approaches that can help you to reduce GI symptoms and improve your performance. Some of these are:

  1. Avoid eating large meals before exercise - allow your stomach 2-4 hours to fully digest the food eaten.

  2. Choose wisely the food you eat - avoid meals rich in fibre and fats too close to your performance as they might worsen your GI symptoms. Why? Because fibre and fats require time to be digested.

  3. Train your gut - having a meal and hydration plan for training and competition days can have been shown to be very helpful in managing GI discomfort.

  4. Avoid training in a dehydrated state as having poor hydration has been linked with damaging the GI tract, especially when athletes train under extremely hot conditions.

  5. Low FODMAP diet - studies that have shown that reducing the consumption of FODMAPs (short-chain carbohydrates) may be helpful for athletes suffering from GI symptoms. A modified FODMAP might help to reduce GI symptoms caused by exercise. However, a low FODMAP diet can be extremely restrictive, especially if self-prescribed. Therefore, consulting a health professional that can lead you in the right direction is always the best approach. Speak to our gut health team if you need a low FODMAP diet.



In general, applying tailored nutritional strategies and adapting food intake to the athlete’s needs may lower the risk of developing GI distress while training.


Francesca is our sports nutritionist who used her sports nutrition expertise while she was a ballet dancer for most of her life. Francesca uses this unique insight to provide clients practical, insightful and lifestyle-driven nutritional advice in both Italian and English. She is a registered associate nutritionist with the AfN. Please visit Francesca's profile to request Francesca's expertise.





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