Physical Activity May Reduce The Incidence Of Breast Cancer

Most cases of breast cancer are thought to be related to lifestyle or environment. However, recent evidence shows secretion of sex hormones such as estrogen may, in some cases, promote the development of breast cancer.

Two recent studies suggest physical activity may influence the secretion of sex hormones in ways that could reduce a woman's chances of developing breast cancer, says Dr. Bob Keith, Extension nutrition specialist with the Alabama Cooperative Extension System.

One study followed more than 25,000 women, ages 20-54, for 14 years. Women who exercised regularly had a 37 percent reduction in the risk of developing breast cancer. A 52 percent reduction in risk was reported among women who performed heavy, strenuous exercise. Overall, the risk of breast cancer decreased as the amount of exercise increased.

Another study of more than 5,000 women found the protective effect of exercise was greatest for women below the age of 60.

Regular, strenuous exercise may reduce the risk of developing breast cancer by causing a reduction in breast tissue exposed to levels of estrogen. Physical activity also may protect against breast cancer by causing a reduction in body fat and body size. In some studies, increases in body fat and size have been associated with increased risk of breast cancer.

No one type of exercise seems to be better, says Keith. Walking, running, cycling, swimming, aerobics, weightlifting and other activities are all beneficial.