Soy food contains substances called isoflavones that has both anti-estrogenic and anti-carcinogenic properties. The study reviewed here investigated the association between breast cancer risk and the intake of soy food in adolescents and adults (Lee S.A., et al. 2009). Food frequency questionnaires were used and 73,223 women participated. The follow up was an average of 7.4 years. The researchers found that adult soy food consumption, measured either by soy protein or isoflavone intake, was inversely associated with the risk of pre-menopausal breast cancer. Women who consistently had a high soy food consumption during adolescence and adulthood had a significant reduced risk for breast cancer. This was however not found for postmenopausal breast cancer. Including soy foods like tofu and roasted soy nuts in your diet seems to be a healthy thing to do. If you are using soy milk be sure it is unsweetened. Reference: Lee S.A. et al, 2009. Adolescent and adult soy food intake and breast cancer risk: results from the shanghai Womenâ€™s Health Study. Am J. Clin Nutr. 2009 Jun;89(6): 1920-6.