Breast cancer product

SCIENTISTS HAVE LONG KNOWN THAT the lower a woman's estrogen level, the lower her risk of breast cancer. Now a study has proven that regular aerobic exercise can reduce that hormone level.

Researchers at the Fred Hutchinson Cancer Research Center in Seattle studied 173 overweight postmenopausal women who had similar lifestyles and didn't use hormone replacement therapy. About half of the women exercised moderately for 45 to 60 minutes, five days a week; the others met once a week for a 45-minute stretching class. By year's end, the women who exercised had up to 17 percent lower estrogen levels, while the levels in the women who stretched stayed the same or increased. (The researchers didn't track who actually got breast cancer.)

Fat reduction seems to be the key to lowering estrogen levels, says lead researcher Anne McTiernan, M.D., Ph.D. Exercise reduces fat, which produces estrogen in women. Postmenopausal women--who are more prone to developing breast cancer because of their age--benefit the most from fat reduction because they produce most of their estrogen in fat. Premenopausal women produce most of their estrogen in their ovaries, even if they're overweight. However, because other research suggests that exercise protects women of all ages from breast cancer, experts think it probably reduces estrogen output from the ovaries, too.

Of course, researchers don't advocate eliminating estrogen from your body altogether. But they say you should work to lower high levels of this hormone, especially if you're overweight. To maximize your breast cancer protection, exercise moderately for 45 to 60 minutes five days a week, says McTiernan. Walking and biking are good options, as is strength training if it gets your heart rate up.