Earlier studies have already shown that exercise lowers the risk of breast cancer. American researchers have now discovered the mechanism behind this. As they write in "Cancer Epidemiology, Biomarkers & Prevention", changes in the oestrogen metabolism play a crucial role.
Scientists from the universities of Minnesota and Pennsylvania studied 391 young, healthy women who had sedentary lifestyles. While 179 of them formed the control group, 212 participants in the intervention group performed moderate to vigorous endurance sports for 30 minutes five times a week for 16 weeks (treadmill, elliptical trainer or stair stepper). The training intensity was adjusted to ensure that the maximum heart frequency was the same in all women.
At the end of the study, the researchers took blood and urine samples on three consecutive days and analysed the amount of three natural oestrogens (E1, E2, E3) and nine of their metabolites. They discovered that in the active group, the oestrogen metabolism increased the metabolite 2-hydroxyestrone (2-OHE1) and produced less 16alpha-hydroxyestrone (16-alpha-OHE1), which significantly increased the 2-OHE1/16-alpha-OHE1-ratio. This reduces the danger of developing mammary cancer.
"Exercise, known to favour fitness and improve heart health, is also likely to help prevent breast cancer by altering oestrogen metabolism", said Mindy S. Kurzer from the University of Minnesota.