Exercise reduces blood estrogens, risk of postmenopausal breast cancer.

2004 MAY 6 - (NewsRx.com & NewsRx.net) -- Three hours of moderate exercise per week significantly reduced circulating estrogens in postmenopausal women participating in a study. The finding may explain why women who exercise regularly lower their risk for breast cancer.

"Exercise is an effective way for postmenopausal women to increase their chances of avoiding breast cancer," said Anne McTiernan, MD, PhD, a member of the Public Health Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, Washington.

McTiernan led a year-long study that examined differences between women who exercised regularly and women who limited their activity to stretching. The study targeted postmenopausal women who were sedentary and overweight or obese at the beginning of the trial.

Within 3 months of undertaking the 5-day per week exercise program, serum levels of estrogens dipped significantly in the more active postmenopausal women, McTiernan and colleagues reported in the journal Cancer Research. After 12 months of routine exercise, women who decreased body fat by more than 2% also had a 16.7% reduction in free serum estradiol, a 13.7% reduction in serum estradiol, and an 11.9% reduction in serum estrone, a less estrogenic form of estrogen. (Estradiol is a female sex steroid with a more potent estrogenic effect than estrone, a different form of estrogen. Estrone concentrations are equivalent to estradiol levels in the blood prior to menopause, but normally increase in postmenopausal women.)

The moderately intensive exercise regimen initially aimed for aerobic activity resulting in the ...