The latest research on breast cancer is good news, it says that regular exercise can reduce the risk.
In a large and detailed analysis on the effects of exercise on premenopausal breast cancer, researchers have found that girls and young women who exercise regularly between the ages of 12 and 35 have a substantially lower risk of breast cancer before menopause.
The study of nearly 65,000 women by researchers in the U.S. found that young women who were physically active, particularly between ages 12 to 22, had a 23 percent lower risk of breast cancer before menopause.
The researchers from Washington University School of Medicine and Harvard University say it is clear that physical activity during adolescence and young adulthood can reduce a woman's risk of early breast cancer.
Lead researcher Professor Graham Colditz, from Washington University, says this is just one more reason to encourage young girls and women to exercise regularly.
A quarter of all breast cancers are diagnosed in women before menopause and these can be more aggressive and harder to treat than breast cancer in older women.
There is ample research which shows that physical activity reduces the risk of postmenopausal breast cancer, however research examining whether exercise can influence the breast cancer risk before menopause, is scant and often conflicting.
The study used data on almost 65,000 women enrolled in the Nurses' Health Study II, where after six years of follow-up, 550 women were diagnosed with breast cancer.
The women had completed detailed annual questionnaires about their levels of physical activity from age 12 on and the researchers found that the incidence rates for invasive breast cancer dropped from 194 cases per 100,000 person-years in the least active women to 136 cases in the most active.