Exercise may lower risk for breast cancer

It’s good for your heart, your brain and your bones. And here’s yet another reason to get some exercise.

A new U.S. study shows that women who engaged in an average of 10-19 hours of physical activity per week — either mild or intense — during their childbearing years were 30 per cent less likely to develop breast cancer after menopause. The same benefit also applied to women who were sedentary earlier in their lives but started exercising after menopause.

For the study, published in the journal Cancer, researchers looked at 3,000 women — with and without breast cancer — who were part of the Long Island Breast Cancer Study Project, an ongoing investigation of possible environmental causes of the cancer.

Participants were asked about their lifetime exercise habits and other lifestyle choices such as smoking and drinking. Other factors such as income and education were also taken into consideration.

The findings? The greatest risk reduction was found in women who exercised at least 10 hours per week. However, exercise at any intensity level — even mild physical activity like walking the dog — was tied to a significantly lower risk, researchers say. Regular physical activity appeared to reduce the risk of hormone receptor positive breast cancers, which are the most commonly diagnosed tumors.

“The observation of a reduced risk of breast cancer for women who engaged in exercise after menopause is particularly encouraging given the late age of onset for breast cancer,” lead researcher Lauren McCullough, of the University of North Carolina at Chapel Hill, said in a news release.

While exercise was linked to a reduced breast cancer risk in post-menopausal women, substantial weight gain may negate these benefits, researchers say. However, women who were overweight when the study started and who exercised had a lower breast cancer risk than those who didn’t participate in physical activity.

And similar to past studies on the topic, the findings indicate an association between exercise and lower breast cancer risk — but the biological processes that link physical activity and breast cancer are still unclear. In other words, more research is needed to prove conclusively that exercise itself was responsible for lower odds of developing breast cancer.

However, McCullough told Reuters Health that exercise could reduce breast cancer risk in several ways, including reducing levels of hormones such as estrogen that can feed tumor development. Exercise can also boost the immune system and the body’s ability to clear cell-damaging free radicals.

“What we can say is, exercise is good for you,” McCullough said. “We don’t know what it’s going to do for any one woman.”


Breast cancer in Canada

Breast cancer affects 1 in 9 Canadian women during their lifetime, according to the Canadian Breast Cancer Foundation. In 2012, it is estimated that 22,700 Canadian women and 200 Canadian men will be diagnosed with breast cancer.

Sources: Journal Cancer online abstract; University of North Carolina at Chapel Hill news release; Reuters Health; National Cancer Institute; CBS; Canadian Breast Cancer Foundation