This review describes the current state of knowledge on the hazards of exercise and the potential benefits of physical activity on the gastrointestinal tract. In particular, acute strenuous exercise may provoke gastrointestinal symptoms such as heartburn or diarrhoea. A substantial part (20-50%) of endurance athletes are hampered by these symptoms which may deter them from participation in training and competitive events. Nevertheless, these acute symptoms are transient and do not hamper the athlete's health in the long term. The only exception is repeated gastrointestinal bleeding during training and competition, which in the long term may occasionally lead to iron deficiency and anaemia. In contrast, repetitive exercise periods at a relatively low intensity may have protective effects on the gastrointestinal tract. There is strong evidence that physical activity reduces the risk of colon cancer by up to 50%. Less convincing evidence exists for cholelithiasis and constipation. Physical activity may reduce the risk of diverticulosis, gastrointestinal haemorrhage, and inflammatory bowel disease although this cannot be substantiated firmly. Up to now, underlying mechanisms are poorly understood although decreased gastrointestinal blood flow, neuro-immuno-endocrine alterations, increased gastrointestinal motility, and mechanical bouncing during exercise are postulated. Future research on exercise associated digestive processes should give more insight into the relationship between physical activity and the function of the gastrointestinal tract.

Irritable bowel syndrome (IBS) is a common chronic disorder that is associated with significant disability and health care costs. The purpose of this paper is to review and assess published randomised controlled trials examining the clinical effectiveness of interventions for IBS for 1987-1998. A literature search was conducted to identify randomised controlled trials of IBS treatments: 45 studies were identified that described randomised controlled trials and of these, six fulfilled all three criteria used to assess the quality of randomised controlled trials, as described by Jadad and colleagues.(1) These criteria are: adequate description of randomisation, double blinding, and description of withdrawals and dropouts. It is concluded that there are few studies which offer convincing evidence of effectiveness in treating the IBS symptom complex. This review strongly suggests that future work should include well designed trials that: describe the randomisation method; use internationally approved diagnostic criteria; and are double blinded and placebo controlled. Clear well defined outcome measures are necessary. Inclusion of quality of life measures allows comparison between trials in different therapeutic areas. Conducting such studies will help to overcome some of the difficulties identified in this review.