Exercise lowers levels of blood estrogens.

2002 AUG 8 - (NewsRx.com & NewsRx.net) -- A regular, moderate-intensity exercise program lowers levels of blood estrogens in postmenopausal women, according to a study led by an investigator from the Fred Hutchinson Cancer Research Center in Seattle, Washington.

The results were presented at the 18th UICC International Cancer Congress in Oslo, Norway.

Funded by the U.S. National Cancer Institute, the study is the first randomized clinical trial to assess the effect of exercise on blood estrogens in postmenopausal women.

The study included 173 women between the ages of 50 and 75 years who were previously sedentary, overweight or obese, and not taking hormone replacement therapy. The women were recruited from the Seattle area. The women were carefully screened for eligibility and were assigned at random to either a moderate-intensity aerobic exercise group or a stretching control group. The exercise group exercised 45-60 minutes, five days a week, for a year. The control group met weekly for a 45-60 minute stretching class for a year.

The exercise program consisted of facility-based and home exercise. The participants met three times a week with an exercise physiologist at an exercise facility, where they performed treadmill walking and stationary biking. They also exercised 2 days a week at home, doing exercises of their own choosing, mostly walking. The exercisers were highly adherent to the exercise intervention: 81% of the exercisers completed 80% or more of their prescribed 225 minutes per week of exercise. Adherence was lower at 12 months than at 3 months. After 1 year, cardiorespiratory fitness increased by 13% in exercisers, and by less than 1% in controls.

At the beginning of the study, there was a strong, statistically significant correlation between body size and levels of estrogens: heavier women had higher levels of all three estrogens studied (estradiol, estrone and free estradiol). After 3 months, women in the exercise group had a 7% 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% decrease in estrone levels compared with a 3% 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 3 months.

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