Teen Exercise May Cut Breast Cancer Risk

“New research shows that exercise during the teen years - starting as young as age 12 - can help protect girls from breast cancer when they're grown. Middle-aged women have long been advised to get active to lower their risk of breast cancer after menopause and now it appears that starting young pays off, too. ‘This really points to the benefit of sustained physical activity from adolescence through the adult years, to get the maximum benefit,’ said Dr. Graham Colditz of Washington University School of Medicine in St. Louis, the study's lead author. Researchers tracked nearly 65,000 nurses ages 24 to 42 who enrolled in a major health study. They answered detailed questionnaires about their physical activity dating back to age 12. Within six years of enrolling, 550 were diagnosed with breast cancer before menopause. A quarter of all breast cancer is diagnosed at these younger ages, when it is typically more aggressive The biggest impact was regular exercise from ages 12 to 22. The women at lowest risk reported doing 3 hours and 15 minutes of running or other vigorous activity a week - or, for the less athletic, 13 hours a week of walking. Typically, the teens reported more strenuous exercise, while during adulthood, walking was most common.”

http://www.boston.com/news/health/articles/2008/05/14/teen_exercise_may_cut_breast_cancer_risk/