Move Your Butt to Save Your Breasts

Breast cancer risks may be lowered with exercise that affects estrogen metabolism

(RxWiki News) We’ve all heard that exercise is good for us. Yeah, yeah…but the couch is more fun, right? Well, there’s a new reason to leave the couch behind.

Researchers have discovered that regular aerobic exercise alters the way estrogen is metabolized.

Because estrogen drives most breast cancers, this research suggests that vigorous physical activity may lower the risk of breast cancer.

"Make exercise a part of your life."

Mindy S. Kurzer, PhD, professor in the Department of Food Science and Nutrition at the University of Minnesota in Saint Paul, and colleagues examined what exercise does within the body that seems to lower the risk of breast cancer.

“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,” Dr. Kurzer said in press release announcing the study results.

Dr. Kurzer and colleagues designed and conducted the Women in Steady Exercise Research (WISER) clinical trial. The study involved 391 sedentary, healthy, young, pre-menopausal women.

The participants were randomly assigned to either continue their sedentary lifestyles (179 women) or to engage in 30 minutes of moderate-to-vigorous aerobic exercise (212 women) five times a week for 16 weeks.

Treadmill, stair steppers or elliptical machines were used, and the workouts were varied so each individual achieved maximal heart rate.

Researchers used advanced technology (liquid chromatography/tandem mass spectroscopy) to measure levels of three parent estrogens, E1, E2 and E3, and nine breakdown products called metabolites in urine samples of participants.

“What the investigators discovered was absolutely fascinating and helps us better understand the association of estrogen exposure and the increased risk of breast cancer,” Brian D. Lawenda, MD, clinical director of Radiation Oncology at 21st Century Oncology in Las Vegas, told dailyRx News.

“After the 16-week study intervention completed, as expected, they found that the women in the exercise group had significant improvements in their body mass composition (less fat mass, more muscle mass) and improved cardiovascular performance,” said Dr. Lawenda, who is founder of

“However, what was most interesting was that the ratio of estrogen metabolites (2-OHE1/16-alpha-OHE1) increased by 25 percent in the women in the exercise group. Previous studies have demonstrated that the higher this ratio of metabolites, the lower the risk of developing breast cancer.

"2-OHE1 is sometimes referred to as a 'good' estrogen metabolite and the 16-alpha-OHE1 as a 'bad' estrogen metabolite due to their inhibitory ('good') or growth stimulating ('bad') effects on cells in the laboratory,” Dr. Lawenda explained.

The study found that aerobic exercise led to an increase in the good metabolite (2-OHE1) and a decrease in the bad metabolite (16alpha-OHE1). There were no changes in the metabolites of the sedentary group.

Dr. Lawenda said, “This study helps us better understand that the anti-cancer effects of exercise are not simply mediated by reducing estrogen, but they appear to be related to the favorable changes in estrogen metabolism.”

This study was published May 7 in Cancer Epidemiology, Biomarkers & Prevention, a journal of the American Association for Cancer Research (AACR).

The project was funded by the National Cancer Institute, the Department of Defense/US Army Medical Research and Materiel Command Congressionally Directed Medical Research Programs and National Center for Research Resources. No conflicts of interest were disclosed.

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Review Date: 
May 6, 2013