Preventing Breast Cancer - National Cancer Institute USA
There is strong evidence that physical activity is associated with reduced risk of cancers of the colon and breast
The National Cancer Institute in the USA says 'There is strong evidence that physical activity is associated with reduced risk of cancers of the breast'.
The National Cancer Institute describe the link in this way:
Reduction in risk
The relationship between physical activity and breast cancer incidence has been extensively studied, with over 60 studies published in North America, Europe, Asia, and Australia.
Most studies indicate that physically active women have a lower risk of developing breast cancer than inactive women; however, the amount of risk reduction achieved through physical activity varies widely (between 20 to 80 percent). (Reference 6,7)
The importance of adolescence
Although most evidence suggests that physical activity reduces breast cancer risk in both premenopausal and postmenopausal women (Lee, above), high levels of moderate and vigorous physical activity during adolescence may be especially protective.
Although a lifetime of regular, vigorous activity is thought to be of greatest benefit, women who increase their physical activity after menopause may also experience a reduced risk compared with inactive women.
Risk reduction can relate to BMI
A number of studies also suggest that the effect of physical activity may be different across levels of BMI, with the greatest benefit seen in women in the normal weight range (generally a BMI under 25 kg/m-squared) in some studies.
The more the better
Existing evidence shows a decreasing risk of breast cancer as the frequency and duration of physical activity increase. Most studies suggest that 30 to 60 minutes per day of moderate- to high-intensity physical activity is associated with a reduction in breast cancer risk. (4,6)