Exercise can lower breast cancer risk
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Consistent observational epidemiologic evidence suggests that physical activity is associated with re- duced postmenopausal breast cancer risk. High endogenous estrogen and androgen levels are fairly consistently associated with an increase in breast cancer risk, whereas increased sex hormone– binding globulin (SHBG) levels are associated with a decrease in risk. 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.
This study, the Alberta Physical Activity and Breast Cancer Prevention Trial, was a randomized controlled trial of exercise was conducted in 320 postmenopausal, sedentary women age 50 to 74 years. Participants were randomly assigned to a 1-year aerobic exercise intervention of 225 min/wk or to a control group who maintained their usual level of activity.
Baseline, 6-month, and 12-month assessments of hormone levels, namely estrone, estradiol, androstenedione, and testosterone were quantified. Women in the intervention group exercised an average of 3.6 d/wk for 178 min/wk.
At 12 months, a significant reductions in estradiol and free estradiol hormone was noted along with increases in SHBG were observed in the exercise group compared with the control group.
This study suggests that physical activity may offer an acceptable means of reducing breast cancer risk for postmenopausal women who are not at a high enough risk for the benefits to outweigh the adverse effects of chemoprevention options that are currently under investigation, particularly given the broad health benefits associated with regular exercise.
Source article: Journal of Clinical Oncology
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