Women who do not engage in regular physical activity may have a higher risk of developing breast cancer [85-87]. Regular exercise can help with weight control, delay the first period until an older age and reduce the frequency of regular menstrual cycles. Each of these can help decrease the total amount of estrogen a woman is exposed to over her lifetime (for more information on estrogen and breast cancer risk, click here) [41]. Low to moderate levels of physical activity may also enhance the immune system's ability to kill cancer cells or slow their growth rate [88].
Though not all the studies of exercise and breast cancer have had consistent results, women who are physically active on a regular basis seem to have about 20 percent lower risk (0.8 relative risk) compared to women who aren't regularly active [89].
Updated 08/14/08
