Gastrointestinal disturbances in marathon runners.

To determine the prevalence of various gastrointestinal disturbances related to long-distance running and its effect on weight, diet and everyday digestive problems, we gave a questionnaire to 279 leisure-time marathon runners, comprising 10% of the participants in a local marathon race. Their answers disclosed a prevalence of dietary changes, weight reduction and altered bowel habits (mainly looser stools and/or more frequent defaecation) of 37, 38 and 48% respectively. A quarter reported earlier long lasting gastrointestinal problems, which improved in 41% of the runners after they started regular training. Thirty-four percent experienced gastrointestinal disturbances during or after running, 20% to such an extent that it seriously affected their performance.