Sunday Dec 21, 2008 (foodconsumer.org) -- Eating soy food regularly may help prevent breast cancer in postmenopausal women, a new study published in the British Journal of Cancer suggests.

The study led by Wu AH and colleagues of the University of Southern California Keck School of Medicine in Los Angeles, California showed that high intake of soy foods was associated with a 18 percent reduction in breast cancer.

The study involved 35,303 Singapore Chinese women enrolled between April 1993 and Dec 1998 in the Singapore Chinese health Study.   Participants were surveyed for their dietary habits using a validated semi-quantitative food frequency questionnaire covering 165 food and beverage items.   During the follow-up through Dec 2005, 628 cases of breast cancers were identified.

After adjusting potential confounding factors, the researchers found high intake of soy was associated with significant reduction in breast cancer risk.   Compared to women with below-median consumption of soy, those with above-media consumption of soy foods were at 18 percent reduced risk of breast cancer.  

The association was mainly confined to postmenopausal women in whom a 26 percent reduction in breast cancer was observed in those who had higher consumption of soy.

The risk reduction was stronger in those with a high body mass index.   Among postmenopausal women who had higher intake of soy, those who had above media BMI had a 23 percent reduction in breast cancer risk compared to 17 percent reduction in leaner women.

The researchers concluded "These prospective findings suggest that approximately 10 mg of isoflavones per day, obtained in a standard serving of tofu, may have lasting beneficial effects against breast cancer development."