Exercise Reduces Breast Cancer Risk

Regular aerobic exercise may reduce a woman’s risk of developing breast cancer by altering estrogen metabolism. Mindy S Kurzer, Ph.D., professor in the Department of Food Science and Nutrition at the University of Minnesota in Saint Paul, and colleagues studied 391 sedentary, healthy, young, premenopausal women. Participants 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 (E1), estradiol (E2), and estriol (E3) – and 9 estrogen metabolites was measured in participants urine collected on 3 consecutive days prior to study initiation and on 3 consecutive days at the end of the study. Results showed that aerobic exercise led to an increase in the amount of the “good” estrogen metabolite 2-OHE1 and a decrease in the amount of the “bad” estrogen metabolite 16alpha-OHE1, thus increasing the 2-OHE1/16alpha-OHE1 ratio, which is associated with a reduction in breast cancer risk. No changes in the 2-OHE1/16alpha-OHE1 ratio were observed in the control group. Professor Kurzer concluded: “Exercise, known to favor fitness and improve heart health, is also likely to help prevent breast cancer by altering estrogen metabolism.”