Aim: To investigate the belief that running causes diarrhoea and gastroesophageal reflux.
Methods: Diet and gastrointestinal symptom questionnaires were completed by 93 randomly selected runners and 95 age, sex matched sedentary controls.
Results: The runners ate more fibre and had more frequent bowel movements which were more often loose or urgent. They had less constipation but there was no difference in the use of laxatives or the prevalence of the irritable bowel syndrome. Although most runners tried to empty their bowels before running, the urgent need to have a bowel movement was still the most common reason for a runner to stop during a run. Heartburn, vomiting and bloating were more common when not training while retching, stitches and fecal incontinence were more common when running. Few runners ate before running and upper gastrointestinal symptoms while running were rare.
Conclusions: Lower gastrointestinal symptoms may be caused by running or the running lifestyle. Upper gastrointestinal symptoms are not due to running alone.