In 2007, a study was published showing that women 20-69 years old who reported doing 6 or more hours per week of strenuous exercise had a 23% reduced risk of invasive breast cancer compared to sedentary women,
A recent study has just shown that women between the ages of 12 and 35 who exercise regularly are 23% less likely to get breast cancer before menopause than less active women. The women with the lowest risk reported either running 3.25 hours a week OR walking 13 hours a week.
A quarter of all breast cancer cases are diagnosed before menopause.
This new study is the largest study so far on pre-menopausal breast cancer. 65 000 women completed questionnaires on their level of physical activity at various periods of their lives, starting from age 12. The researchers followed up over six years and found that 550 women had been diagnosed with breast cancer.
The researchers concluded that the benefits of exercise weren’t linked to a particular sport or intensity, but to the total activity.
Both this study and the 2007 one speculate that women who are more active have a lower breast cancer risk because they tend to menstruate later in life and are therefore exposed to less estrogen. Women exposed to more estrogen have a greater breast cancer risk.
Bottom line: it’s important for girls to start being more physically active early on- in their teens and early adulthood- to help reduce their risk of developing breast cancer. Of course, being more physically active can also help prevent obesity and it’s complications- type 2 diabetes, heart disease, high blood pressure.
http://www.theglobeandmail.com/servlet/story/RTGAM.20080514.wlcancer14/BNStory/lifeMain , http://www.cbc.ca/health/story/2007/02/16/breast-cancer-exercise.html , http://ap.google.com/article/ALeqM5gQwQoRDjVs27bJQ6x2mvef_wEVCwD90KVP400