Breaking a sweat does more for your body than just trim your waistline. Exercise may lower a woman’s risk for breast cancer and researchers are finding out why.
Scientists from the University of Minnesota in St. Paul conducted a study of 391 inactive, healthy, premenopausal women whom they split into two groups. They found that the 179 women in the intervention group, who received 30 minutes of moderate-to-vigorous exercise five times a week for over 16 weeks, showed changes in their estrogen metabolism that could explain the anti-cancer benefits of working out.
“Ours is the first study to show that aerobic exercise influences the way our bodies break down estrogens to produce more of the ‘good’ metabolites that lower breast cancer risk,” said Mindy Kurzer, a professor in the Department of Food Science and Nutrition at the University of Minnesota in a statement.
The researchers measured the levels of three parent estrogens, E1, E2 and E3, and nine breakdown products called metabolites in the women’s urine samples. At the end of the study period, the exercise group had healthier BMIs and cardiovascular sustainability, but they also had a 25% increase in the metabolite ratio 2-OHE1/16-alpha-OHE1, which has been linked to a lower breast cancer risk. More 2-OHE1 and less 16-alpha-OHE1 have been associated with a lower risk since 16-alpha-OHE1 is thought to encourage cancer cell growth.
These changes were not seen in the control group of women who did not exercise over the study period, according to the study, which appears in the journal Cancer Epidemiology, Biomarkers & Prevention.
The findings give cancer researchers more insight into how exercise interacts with estrogen to reduce cancer risk. This is especially important since estrogen is a large contributing factor in breast cancer development.
If exercise can help women protect themselves against breast cancer, they’ll be eager to know just how much effort can provide a measurable benefit, which is what researchers at the University of North Carolina at Chapel Hill are exploring. Last June, the researchers studied more than 3,000 women between the ages 20 to 98: 1,504 women with breast cancer and 1,555 women without the disease who were participating in the Long Island Breast Cancer Study Project.
They found that women who did any exercise at all had a 6% lower risk of breast cancer than sedentary women. However, women who had children and exercised about 10 to 19 hours each week either during their reproductive years or after menopause experienced a much greater benefit, with a 30% lower risk of breast cancer compared to women who exercised less or were inactive.
Currently, national guidelines recommend people get about 150 minutes of moderate exercise a week, which is about half an hour of brisk walking five times a week. Although more research is needed to confirm the underlying mechanisms driving the protective benefits of exercise, working out regularly remains an easy way to encourage good health overall.