Two Studies Shed Light on the Link Between Fitness and Breast Cancer

by Helen Zhang, age 15

Studies conducted by the American Cancer Society and the University of Minnesota indicate that exercise may be a vital key to reduce the risk of breast cancer. Two reports published in the journal Cancer Epidemiology, Biomarkers & Prevention detail the positive influence of exercise and explain the study’s conclusions.

The latest and largest study conducted at American Cancer Society followed 73,600 postmenopausal women, aged 50 to 73, for almost two decades. Researchers collected survey data on the lifestyles and activities of these women. About half the group reported walking as their only form of exercise. Over the course of the study, 4,760 of the women developed breast cancer.

The researchers ultimately discovered that women who walk at least seven hours per week have a 14 percent lower risk of developing breast cancer than those who walk fewer than three hours per week. Furthermore, the most active women—those who exercised up to ten hours per week—reduce their risk of developing breast cancer by 25 percent in comparison to the least active women.

The second study done by public health research at the University of Minnesota looked at younger, non-active women and their estrogen levels. The study was split into two groups—those in the first group remained sedentary while those in the second group attended an aerobic exercise program five times a week for four months. Researchers tested levels of estrogen and estrogen metabolites, substances that form when estrogen is broken down, through urine samples of the participants.

By looking at the ratios of different estrogen metabolites, researchers can determine breast cancer risk. The results showed the sedentary group had no change in their estrogen metabolites; however, the active group’s ratio of metabolites indicated a lower risk of cancer. In addition, the active women lost body fat and gained muscle.

The ability of exercise to change the ratio of estrogen metabolites and to lower body fat levels may reduce risks of breast cancer. However, this study does not prove that exercise can eliminate all chances of cancer. Exceptions exist; even those who are very active can develop cancer.

“There is still a very great deal that we don’t know,” says Dr. Alpa V. Patel, a senior epidemiologist at the American Cancer Society and senior author of the first study. She adds that walking is an easy, inexpensive type of exercise for everyone. “But physical activity, and especially walking, are so simple and so accessible to most women. So why not?”

[Source: New York Times]