"In men who met the study's exercise prescription of an hour of aerobic activity per day, six days a week for a year, we saw a substantial decrease in the amount of cellular proliferation in the areas of the colon that are most vulnerable to colon cancer," said lead author Anne McTiernan, M.D., Ph.D., an internist and epidemiologist who directs the Hutchinson Center's Prevention Center. "However, we found that even four hours or more of exercise weekly was enough to produce a significant benefit," she said.
The researchers found an inverse relationship between the amount and intensity of exercise and the levels of cellular proliferation, as measured by how far the migrating cells travelled from the base of the crypt and up the sides toward the surface of the epithelium.
A significant decline in cellular proliferation was observed among men who worked out an average of four hours a week or more and in those whose cardiopulmonary fitness was most robust. The greatest decrease in cellular proliferation was seen in men who exercised more than five hours a week. No such decrease was seen among sedentary men or those who exercised infrequently.
"Proliferation in the upper section of the colon crypt decreased among those exercising for a mean 250 minutes per week or greater, which is important because this pattern of proliferation is most associated with risk for colon cancer," the researchers reported.
Body weight did not appear to have an impact on the effect of exercise on cellular proliferation. However, the investigators saw no notable changes in markers of cellular proliferation in their female counterparts. "This finding supports previous epidemiological studies that also have suggested that regular exercise reduces the risk of colon cancer in men more than in women," McTiernan said. "It's not a finding that we really wanted to see, but at least our results are consistent with those of previous population-based, epidemiological studies."
MEDICA.de; Source: Fred Hutchinson Cancer Research Center