Runners Colitis : How A Regular Runner May End Up Getting The Runs!

If you decided to read this post, chances are you’ve nearly done a ‘Radcliffe’ when running…and if you’re unfamiliar with what a Radcliffe is then Google ‘Paula Radcliffe poo’s herself’ and brace yourself. Now I don’t suggest this to torment or belittle one of the greatest long distance runners our country have ever produced, but rather to illustrate (albeit rather graphically) the effects long distance running can have on the digestive tract!

Runners are more susceptible to upset stomachs

It is common for an ultra endurance athlete to suffer with gastrointestinal upsets, or the s&%*s as it’s more commonly referred to in the sporting industry. This can include both vomiting and diarrhoea, with studies reveal that between 19 and 26% of marathon runners suffer with running related diarrhoea. This onset of loose bowels is basically inflammation of the bowel, otherwise known as runners colitis. These stomach upsets may consist of stomach cramping, diarrhoea and even bleeding, so as you can appreciate, this is quite damaging to an athletes performance!

What are the causes of runners colitis?

The overconsumption of fluid and carb based drinks is widely regarded to be one of the main causes of gastrointestinal upsets such as runners colitis (Tipton & Luc van Loon, 2013). Tipton and Luc van Loon state that the human body can usually absorb, and thus tolerate around 100g of carbohydrate per 1 hour, any more than this may lead to gastrointestinal upsets and accidents. Another main cause might include ischemia i.e. a reduced flow of blood to the gastrointestinal tract (stomach and intestines) during exercise, as well as dehydration. So this takes us back to the importance of getting fluid levels and electrolytes right, as much as too much fluid can cause upsets, too little fluid can also lead to stomach pain and upsets.

The jarring nature of running is the problem

The high impact, jarring nature of running is one of the main causes of runners colitis, the physical action of the intestine bouncing around in the stomach can result in physical injury to the intestinal wall, more precisely the colon. The damage to the colon is what usually causes the loose bowels and blood in the stool (poop), and Doctors acknowledge that the occasional episode is not an immediate cause for concern, but if it persists it is worth contacting your Doctor or health professional for more advice.

How to minimise the onset of runners colitis

Mindful eating is a very good place to start. What you eat, when you eat it, and how much you consume will profoundly effect your stomachs response during exercise. Other variables that may influence the onset of runners colitis include medication, supplementation and caffeine, so all factors need consideration. Eberle, (2014) asserts the your best course of action for preventing, or at least limiting the onset of runners colitis is to drink plenty of fluid both before and during exercise. Your bodies natural response to exercise is to preferentially shift blood and fluid from your colon to the muscles and skin in order to disperse heat, so dehydration reduces the blood volume in turn starving the intestine of even more blood. This lack of blood in the intestine is what ultimately damages the inner lining of the intestine, resulting in stomach discomfort, loose bowels and ultimately runners colitis.

Aim to drink as much as you can in the early stages of a race, this is because as the race progresses the body slowly becomes more and more dehydrated, and the more dehydrated the body is, the less efficient it is at replacing fluid losses.


Eberle, S, G. (2014). Endurance Sports Nutrition. Fuel your body for optimal performance. 3rd Ed. Runners Colitis. IL: Human Kinetics.

Tipton, K, D & Luc van Loon, J, C. (2013). Nutritional coaching strategy to modulate training efficiency. Basel: Karger

About the Author

Job Role Qualified Dietitian and Sports Nutritionist Qualifications BSc (Hons) Sports Science | BSc (Hons) Dietetics Tom has always participated in sport both recreationally and competitively which led to an unquenchable thirst for information on anything health, nutrition and fitness. After leaving school Tom went on to play for a football academy during which time he studied Sport and Exercise Science. From here he went on to study a BSc (Hons) Sport Science at UEA followed by his second BSc (Hons) degree, this time at the University of Hertfordshire studying Dietetics. Tom has worked in the fitness, educational and clinical nutrition industry starting out at David Lloyd Health and Leisure Clubs. He then went on to work as a Dietitian (RD) in the NHS, during which time he conducted clinics for healthy eating, weight loss and weight gain, as well as specialised consultations on Diabetes, IBS and Coeliac disease to name a few. He has vast amounts of experience at devising diet plans and supplement regimens, as well as working in the community with schools and competitive athletes. As Head Nutritionist and Supplement expert at Discount Supplements Tom is here to provide current and evidence based health and nutrition information to help you reach your health and fitness goals!
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