Soy Intake and Risk of Breast Cancer in Asian-Americans Principal investigator: Anna H. Wu, USC, Los Angeles Co-investigator: Peggy Wan Abstract This population-based case-control study of breast cancer in Asian-Americans was designed to investigate the causes of their increased breast cancer rates as compared to their rates in Asia. Specifically, our primary objective was to test the hypothesis that a diet rich in soy products reduces the risk of breast cancer. Our secondary objectives were to investigate the role of other dietary and (e.g., vegetables and fruits, dietary fiber and specific micronutrients, total and specific components of fat) non-dietary factors (e.g., physical activity, body size, menstrual and reproductive characteristics) in the etiology of breast cancer in Asian-Americans. This analyiss is based on complete interviews with 600 Asian-American women (Chinese, Filipino, Japanese), ages 25 to 74, who were diagnosed with biologically-confirmed primary breast cancer identified in Los Angeles County. A comparable number of Asian-American women(controls) without breast cancer matched to cases on age ethnicity and neighborhood of residence served as the comparison group (350 cases and 350 controls interviews were funded under 1RB-0287; additional subjects were recruited under funding from 3PB-0102 and 5PB-0018). Intake of soy foods (mg. of isoflavone per day) was influenced by birthplace and Asian ethnicity. Among control subjects intake was highest among Chinese (27 mg/day), intermediate among Japanese (19 mg/day), and lowest among Filipino women (9 mg/day). Intkae of soy was more than double among Asian women born in Asia compared to those born in the United States. The risk of breast cancer was significantly influenced by soy intake during adolescence and adult life. After adjusting for age, Asian ethnicicy, education, and migration history, women who reported soy intake 4 or more times per week during adolescence showed a 40% reduced risk of breast cancer compared to those who did not consume any soy (p<0.05). There was also a significant trend of decreasing risk with increasing quartile level of soy intake during adult life (p<0.05). The reduction in breast cancer risk associated with soy intake was observed among Asian migrants as well as women born in the US. Soy intake during adolescence and adult life conferred independent protective effects against breast cancer risk in this population. We are continuing to analyze these data to evaluate the soy-breast cancer association by menopausal status. We are also investigating the interrelationships between soy intake and other dietary and non-dietary risk factors to determine whether residual confounding may play a role in the observed soy-breast cancer association. Remember we are NOT Doctors and have NO medical training. This site is like an Encylopedia - there are many pages, many links on many topics. Support our work with any size DONATION - see left side of any page - for how to donate. You can help raise awareness of CAM.