Asian-American women who consumed soy foods on a weekly basis during their teen years and adulthood had about half the risk of developing breast cancer compared to similar women who ate little soy during the same time periods, according to a study in the September issue of Carcinogenesis.
Risk also was somewhat lowered for women who ate soy regularly during the teen years but consumed little during adulthood. However, preliminary data suggest little added benefit for women who ate little soy during adolescence but a high amount of soy during adulthood.
"There has been a lot of talk and controversy about the Asian diet and connections between soy food intake and breast cancer. We wanted to look at soy very carefully, to better understand if soy by itself is protective or if the level of soy consumption is just a marker for acculturation," says Anna H. Wu, Ph.D. professor of preventive medicine at the Keck School of Medicine.
Wu and colleagues conducted a case-control study of breast cancer among Chinese, Japanese and Filipino women in Los Angeles County, specifically looking at the importance of soy. From 1995 to 1998, they interviewed 501 Asian-American breast cancer patients and compared them to 594 healthy Asian-American women.
The researchers asked about eating habits, including how many times each week during adolescence they ate tofu. They also asked about the frequency and amounts of whole soy foods, such as tofu, soymilk, miso and fresh soybeans, usually eaten during adulthood.
Intake was highest among Chinese (26.8 milligrams of isoflavones a day), intermediate among Japanese (18.4 mg of isoflavones a day) and lowest among Filipinas (9.3 mg of isoflavones a day). Migrants ate a little more
Contact: Jon Weiner
University of Southern California