Two new studies of pre- and post-menopausal women suggest that regularly engaging in physical activity — particularly walking — can significantly reduce a woman’s risk of breast cancer by changing how her body handles the hormone estrogen.
While it’s certainly not news that exercise has been shown in the past to reduce cancer risk, it’s taken scientists a while to figure out exactly how exercise works to help lower cancer risk and whether there is a certain type or amount of exercise that is best.
One of the studies, recently published in Cancer Epidemiology, Biomarkers & Prevention, found that women who reported that their primary physical activity was walking for seven hours per week — about an hour a day — had a 14% less chance of developing breast cancer than those who walked for fewer than three hours per week.
Being even more physically active held an even greater benefit: participants who said that they regularly exercised more vigorously — spending around ten hours per week doing activities like running, swimming, and singles tennis — had 25% less risk of developing breast cancer. Regardless of how much any of the women weighed or whether they used hormone replacement therapy, the risk reductions held true.
The other study, published in the same journal back in May, took sedentary pre-menopausal women and divided them into two groups: those who would remain sedentary, and those who would begin a moderate aerobic exercise program. Throughout the study, the women were regularly tested for their estrogen levels and for substances in the blood that indicate that the body is processing estrogen.
After four months, the sedentary participants showed no changes, but the active participants showed changes in their blood that researchers believe correspond to a reduced cancer risk. They also built muscle and lost body fat, which is important for more than just cosmetic reasons. After menopause, the estrogen in a woman’s body comes mainly from her fat cells and not her ovaries. Exercising and reducing body fat can help the body to produce less extra estrogen and more effectively process the estrogen it has.
There’s still a lot to be learned about cancer — how it starts, why it happens in some people, why it doesn’t happen in others. But if something simple like going for a walk each day can significantly reduce your risk of breast cancer, then there’s no time like the present to lace up your sneakers and take the first steps towards a healthier life.