Exercise May Lower Risk of Breast Cancer
It’s been apparent for years that women who exercise after surviving breast cancer do better than survivors who are less active. Exercise appears to improve physical, psychological and functional well being among survivors, and it even reduces the risk that certain types of tumors will recur. But that’s not all. Observational studies indicate that women who exercise regularly are less likely to get breast cancer to begin with.
But until recently, scientists didn’t really know why. They suspected that exercise somehow influences estrogen, which plays a role in some forms of breast cancer. Now a new study by researchers at the University of Minnesota suggests that the mechanism may indeed have to do with exercise-induced changes in the way estrogen is metabolized.
“Estrogen” is a general term for what’s actually a handful of similar, but different, hormones. There are several forms, and it’s long been suspected that women who have more of a form with weak estrogenic activity (2-hydroxyestrone) are less likely to develop hormone-related cancers than women with higher levels of a form (16α-hydroxyestrone) that has strong estrogenic activity. Diet has an influence on this ratio of weak/strong estrogens in the body, and so does exercise. For instance, foods high in natural estrogen-like compounds, like soy, appear to provide some protection against cancer by promoting a more favorable ratio of these estrogens in the body.
And according to the new study out of St. Paul, aerobic exercise promotes this favorable ratio of estrogens, too. Researchers proved this by monitoring estrogen levels among young, sedentary women who were recruited to exercise regularly, or not, during the study. Among women who exercised at moderate-to-vigorous intensity for a half-hour per day, for four months, the “good” estrogen levels climbed, while levels of “bad” estrogen” fell. Women who remained sedentary experienced no changes in the ratio of estrogens.
Bentz AT, Schneider CM, Westerlind KC. The relationship between physical activity and 2-hydroxyestrone, 16alpha-hydroxyestrone, and the 2/16 ratio in premenopausal women (United States). Cancer Causes Control. 2005 May;16(4):455-61.
Keegan TH, Milne RL, Andrulis IL, Chang ET, Sangaramoorthy M, Phillips KA, et al. Past recreational physical activity, body size, and all-cause mortality following breast cancer diagnosis: results from the Breast Cancer Family Registry. Breast Cancer Res Treat. 2010 Sep;123(2):531-42. doi: 10.1007/s10549-010-0774-6. Epub 2010 Feb 7.
Morimoto Y, Conroy SM, Pagano IS, Isaki M, Franke AA, Nordt FJ, Maskarinec G. Urinary estrogen metabolites during a randomized soy trial. Nutr Cancer. 2012;64(2):307-14. doi: 10.1080/01635581.2012.648819. Epub 2012 Jan 31.
Parrish MR, Martin JN Jr, Lamarca BB, Ellis B, Parrish SA, Owens MY, et al. Randomized, placebo controlled, double blind trial evaluating early pregnancy phytonutrient supplementation in the prevention of preeclampsia. J Perinatol. 2013 Feb 28. doi: 10.1038/jp.2013.18. [Epub ahead of print]
Schmidt ME, Chang-Claude J, Vrieling A, Seibold P, Heinz J, Obi N, et al. Association of pre-diagnosis physical activity with recurrence and mortality among women with breast cancer. Int J Cancer. 2013 Feb 27. doi: 10.1002/ijc.28130. [Epub ahead of print]
Smith AJ, Phipps WR, et al. The Effects of Aerobic Exercise on Estrogen Metabolism in Healthy Premenopausal Women. Cancer Epidemiol Biomarkers Prev. May 2013 22; 756.
Steindorf K, Ritte R, Eomois PP, Lukanova A, Tjonneland A, Johnsen NF, et al. Physical activity and risk of breast cancer overall and by hormone receptor status: the European prospective investigation into cancer and nutrition. Int J Cancer. 2013 Apr 1;132(7):1667-78. doi: 10.1002/ijc.27778. Epub 2012 Sep 14.