Exercise and cancer. An epidemiologic short review of the effects of physical activity on carcinoma risk
Marti, B.
Schweizerische Medizinische Wochenschrift 122(27-28): 1048-1056
1992
ISSN/ISBN: 0036-7672 PMID: 1631518 Document Number: 401979
It is only during the past decade that occupational and leisure-time physical activity--whose importance for the prevention of cardiovascular diseases is well documented--has become a focus of research in cancer epidemiology. The most consistent observation of more than 15 epidemiological studies published in the 1980s is an average increase in the risk of colon cancer of 75 to 80% for physically inactive men and women, as compared to their more active counterparts. No study at all found a direct relationship between physical activity and colon cancer risk. A hypothetical explanation for this likely but unproven protective effect of regular exercise against colon cancer is that physical activity stimulates colon peristalsis, hereby reducing enteral transit time and diminishing exposure of the intestinal mucosa to fecal carcinogens. The epidemiologic evidence for a protective effect of exercise against rectal cancer and other cancers, however, is not sufficient. Isolated observations of a direct relationship between physical activity and the risk of cancer (e.g. prostate) have even been reported. For women, there is preliminary evidence of a protective effect of athletic activity against cancers of the breast and the reproductive system for which hormonal factors may be responsible. The cancer-protective effect of exercise per se is apparently too modest to serve as a justification for a general recommendation to take regular exercise.