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Exercise Might Reduce Breast Cancer Risk by Altering Sex Hormones

Posted Feb 18 2010 6:41am
Exercise is an important part of a healthy lifestyle and critical to maintaining a healthy body weight.  As I've discussed in previous blogs, exercise also has been reported to reduce breast cancer risk; however, the mechanism by which breast cancer risk is reduced is uncertain.  Research studies suggest that exercise might reduce breast cancer risk by lowering sex hormone levels, altering production of insulin-like growth factors, or by reducing chronic inflammation.  This is an active area of research that I expect will yield some fascinating results over time.

One new research study explored the effects of aerobic exercise on sex hormone changes.  In this new study, researchers assigned 320 postmenopausal, sedentary women between 50-74 years of age to either (1) a control group who maintained their normal level of activity or (2) an exercise group where they were asked to exercise for 225 minutes per week for 1 year.  Blood levels of sex hormones were measured at the beginning of the study and after 6 and 12 months.  While no differences in estrone, androstenedione or testosterone levels were observed after 12 months, women in the exercise group had lower levels of total estradiol, lower levels of free estradiol, and higher levels of sex hormone - binding globulin (SHBG), a hormone that binds up estrogens.

The results of this study are a step in the right direction towards determining why exercise helps to reduce breast cancer risk.  Increased estrogen levels, particularly estradiol, are an important risk factor for breast cancer progression.  The National Cancer Institute indicates that while estrogen does not appear to directly cause DNA mutations that lead to the development of breast cancer, estrogen can stimulate growth of breast cancer cells.  Therefore, reducing estrogen levels or at least maintaining healthy estrogen levels can be an important part of reducing breast cancer risk.  This new study suggests that exercise might be one way to lower our body's production of estradiol and reduce breast cancer risk.

In addition to getting enough exercise, there are many things we can all do to reduce our breast cancer risk.  Read my book Fight Now: Eat & Live Proactively Against Breast Cancer ( to learn more.
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