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What can I do to reduce gut symptoms during running?

Feb 07, 2024

It's no secret that runners often experience a range of gastrointestinal issues during their training and races. From the runner's trots, which has gained notoriety, thanks to athletes like the former female marathon world record holder Paula Radcliffe, to the less glamorous yet equally unpleasant gas and bloating, exercise associated gut symptoms can truly spoil your run.

Up to 96% of ultramarathon runners experience some sort of gastrointestinal distress during a race, with 60% of runners reporting severe symptoms. Gut symptoms during exercise are more common in females, hot weather, high intensity exercise, those with irritable bowel symptoms (IBS) day-day, those who have gut symptoms in the past and runners vs other sports. That's right, it's not just you and your sensitive stomach!

What factors can contribute to exercise-associated gut symptoms?

During exercise there can be altered digestion and absorption of food and fluids. This occurs through re-direction of blood from the gut to the muscles, changes in the rate of movement of food and fluids through the gut and the stress response. This may trigger a range of gut symptoms including:

  • upper gastrointestinal symptoms: belching, vomiting, heartburn, bloating
  • lower gastrointestinal symptoms: abdominal cramping, flatulence, urge to defecate, diarrhoea, bleeding
  • other related gastrointestinal symptoms: nausea, dizziness, urge to urinate, side ache (“stitch”)

Some factors can contribute to increased frequency and severity of exercise-associated gut symptoms including:

  • consuming too much carbohydrate, fibre, fat, protein, fermentable carbohydrates (FODMAPs) or caffeine prior to and/or during exercise
  • consuming large volumes of food or fluid in a short time period
  • poor feeding tolerance (i.e. inadequate gut training)
  • stress
  • over- or under hydration
  • circadian variation (more symptoms during night vs day time)
  • heat stroke
  • hyponatraemia or hypernatraemia (too little or too much salt in the blood)
  • medications and/or supplements
  • underlying health conditions

How do I identify the cause of my gut symptoms?

It is important to identify the factors that are contributing to your exercise-associated gut symptoms. This may take time and include assessments such as hydration studies, monitoring of your diet prior to and during exercise and consideration of other health issues.

What strategies will improve my gut symptoms?

Some strategies that may improve gut symptoms include gut training, heat adaptation strategies, improving hydration status, carbohydrate feeding and different carbohydrate formulations. You will need to practice different strategies and monitor whether these are helpful in improving your symptoms. Supplements like arginine, citrulline, antioxidants, glutamine, probiotics, and curcumin, however, have not been shown to improve exercise-associated gut symptoms.

How can gut training help?

Gut training involves gradually increasing the amount of food and fluid you consume during exercise to improve your gut's tolerance. There are various gut training strategies that may help, e.g. running straight after a meal, training with a relatively large volumes of fluid, simulating your race nutrition plan, increasing carbohydrates in your diet and training with a relatively high carbohydrate intake during exercise.

How can heat adaptation help?

Heat adaptation strategies are relevant for those training and/or racing in warm or hot climates. This involves specific protocols, that improve your ability to regulate your temperature and sweat more efficiently. By improving your ability to tolerate higher temperatures and sweat more efficiently, you can also improve your ability to digest food during exercise.

How can hydration help?

Proper hydration is crucial for runners, not only to maintain performance but also to reduce gut symptoms. Dehydration is known to increase gut symptoms, and once the body is dehydrated, it becomes more difficult to reverse the fluid deficit. Guzzling large volumes of fluid can, therefore, make gut symptoms worse. Drinking too much fluid can lead to a condition called hyponatremia (low blood sodium) which cause nausea, vomiting, and other gut symptoms. Understanding your hydration requirements and planning your fluid appropriately to avoid under- or overhydration can reduce your risk of gut symptoms.

How can different carbohydrate formulations help?

Reducing FODMAPs before exercise can help some athletes reduce gut symptoms. FODMAPs are types of carbohydrates that are not well absorbed in the small intestine and can be rapidly fermented by gut bacteria, causing gas, bloating, and other gut symptoms that can be exacerbated during exercise. Studies show that following a low FODMAP diet for a short period (1-6 days) can reduce gut symptoms during exercise. In the long-term, low FODMAP diets can lead to nutrient deficiencies and negative impacts on gut health. Talk to an Accredited Sports Dietitian before considering a low FODMAP diet.

Including multiple transportable carbohydrates (glucose and fructose) in your fueling may improve gut symptoms during prolonged exercise compared to ingesting glucose alone, particularly when targeting high fuel intakes. Additionally, consuming lower concentrations of carbohydrate (6-8%) may also help reduce the incidence of gut symptoms compared to higher concentrations (10%).


You don't have to put up with unpleasant gut issues! It is important to recognise that each runner's gut symptoms are caused by unique factors and there is no one-size-fits-all solution. Reach out and I can guide you through identifying the cause of your gut symptoms and the best management strategies so you can move forward without worrying about your gut.

Download my FREE ebook here to find out my secrets to fueling for a PB!


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