Regular exercise and healthy lifestyle offers many health advantages and those who do exercise on a regular basis have a lower incidence of various chronic diseases, they have lower stress levels and are reported as having a better quality of life than those do no exercise. However, any direct relationship between frequent exercise and cancer is not particularly well understood and this article looks at a recent Canadian study (1) between increased activitiy in post-menopausal women and breast cancer risk factors.

The lack of exercise may increase the chance of developing cancer through a number of different mechanisms. These include having increased levels of oestrogens and testosterone through lack of exercise and a suppressed immune function. Research studies have been carried out that have shown that physical activity and diet interventions can change biomarkers of cancer risk.

In a 2010 Canadian study (1), 320 postmenopausal women were divided randomally into an exercise group and a control group. The exercise group were asked to perform a structured exercise program of at least 45 minutes of aerobic exercise 5 days a week for a year (at around 70% of maximum heart rate). The control group were just asked to continue at their usual level of activity.

When the data was analysed, the researchers found that there were statistically significant reductions in levels of estradiol and free estradiol, as well as increases in sex hormone-binding globulin (SHBG), among the exercising women compared to the control group. Although these hormonal changes were modest, the researchers stated:

"This trial found that previously sedentary postmenopausal women can adhere to a moderate- to vigorous-intensity exercise program that results in changes in estradiol and SHBG concentrations that are consistent with a lower risk for postmenopausal breast cancer."