ad higher levels of all three estrogens studied (estradiol, estrone and free estradiol). After three months, women in the exercise group had a 7 percent decrease in the level of estradiol, the most potent blood estrogen, while women in the stretching group had no change in estradiol levels. Among exercisers, there was a 4 percent decrease in estrone levels compared with a 3 percent increase in controls, and the difference was statistically significant. After 12 months, there was still a difference in blood estrogens between exercisers and controls, although the effect was lower than at three months.

Among the exercisers who lost body fat, the effect of exercise was strongest: exercisers who lost more than 2 percent of their initial body fat had a 14 percent decrease in estradiol levels. Controls who lost body fat, however, did not experience a decrease in estradiol levels.

The changes in estrogen levels were not due to dietary changes; on average, exercisers did not change the amount of calories they took in, and controls had only a slight, decrease in calorie intake.

High estrogen levels high risk
The results of this study are very significant, says principal investigator Anne McTiernan, M.D., Ph.D., director of Fred Hutchinson's Prevention Studies Clinic and Exercise Testing and Training Center, and a member of the center's Cancer Prevention Research Program in the Public Health Sciences Division.

"We know that women still make estrogen after menopause, although they make it in their fat cells instead of in their ovaries. Women who have high blood-estrogen levels after menopause have a high risk of developing breast cancer. Therefore, it is important to find ways to lower estrogen levels for women who want to lower their risk of breast cancer," says McTiernan, also a research associate professor at the University of Washington schools of Public Health and Medicine.

"Previous studies have found associations bet
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Contact: Hanna Hanes
hhaanes@online.no
Norwegian Cancer Society
4-Jul-2002

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