Healthnotes Newswire (November 30, 2006)—Several studies have suggested that people who exercise regularly are less likely to develop colon cancer. A new trial shows that men might curtail some precancerous changes in the colon by getting physically active.

According to the American Cancer Society, colon cancer is the second leading cause of cancer-related deaths. The disease usually occurs in people over the age of 50, but certain genetic traits can increase the risk of developing colon cancer at a younger age. People who have a type of abnormal growth (polyps) in the colon are also more likely to get colon cancer, as are people with inflammatory bowel disease: Crohn’s disease and ulcerative colitis.

Diets high in animal fat, red meat, and processed meats while low in fruits and vegetables have been linked to colon cancer. Being overweight and smoking can increase your risk, as well.

People who are at an increased risk for colon cancer have a faster rate of colon cell turnover—the speed at which the cells grow, die, and are replaced—than do healthy people. This faster turnover rate is considered a precursor to colon cancer.

In a new study designed to see if physical exercise could slow the rate of colon cell turnover, over 200 people between the ages of 40 and 75 were assigned to a group that did not receive any special instructions about exercise or a group that was asked to engage in moderate to vigorous physical exercise for one hour per day, six days a week for one year.

Among the men who exercised for at least 250 minutes each week, several measures of colon cell turnover decreased. Men who exercised for more than 300 minutes each week had even lower rates of cell turnover.

In the report, published in Cancer Epidemiology, Biomarkers and Prevention, the researchers concluded, “This suggests that the [earlier] observations of reduction in colon cancer risk with regular exercise are likely to be real and that exercise may reduce colon cancer risk through an alteration in [cellular turnover rates].”

The same effects were not seen among the women. “One possible explanation may be that with increased exercise, estrogen levels decrease,” the authors suggested. Higher estrogen levels reduce colon cancer risk, potentially counterbalancing the beneficial effect of exercise.

(Cancer Epidemiol Biomarkers Prev 2006;15:1588–97)