Exercise may reduce the risk of breast cancer

Researchers recently showed that a lifestyle intervention (exercise) reduced the 'bad' estrogen and increased the 'good' estrogen.  Premenopausal women (391 sedentary, healthy, young) were randomly assigned to 1 of 2 age-matched, body mass index-matched groups: a control group of 179 women and an intervention group of 212 women. Women in the intervention group performed 30-minutes of moderate-to-vigorous aerobic exercise 5-times a week for 16-weeks. The amount of 3 parent estrogens – estrone, estradiol, and estriol – and 9 estrogen metabolites were measured in subjects urine collected on 3 consecutive days prior to exercise and on 3 consecutive days at the end of the study.

This is what they found:

"... in healthy premenopausal women, an exercise regimen of 150 minutes of moderate-to-vigorous aerobic exercise per week for 16 weeks resulted in significant changes in estrogen metabolism in a direction consistent with reduction of breast cancer risk."

2-OHE1/16a-OHE1 increased significantly (P = 0.043), whereas E1 decreased significantly  (P = 0.030) in control participants (n = 153). The change from baseline in 2-OHE1/16a-OHE1 was significantly different between groups (P = 0.045), even after adjustment for baseline values.

Alma J Smith, William R Phipps, William Thomas, Kathryn H Schmitz, and Mindy S Kurzer. The effects of aerobic exercise on estrogen metabolism in healthy premenopausal women. Cancer Epidemiol Biomarkers Prev. 2013;22:756-764.