Cohort study of tofu intake and prostate cancer: no apparent association.

Three case-control studies and one cohort study have suggested that soy products reduce the risk of prostate cancer (1-4), but overall evidence from these epidemiologic studies is still limited. To investigate this issue further, we conducted a cohort study on the association of tofu (soybean curd) intake with prostate cancer among Japanese Americans in Hawaii. The annual mortality rate of prostate cancer among Japanese American men is 11.7 per 100,000, which is lower than the mortality rate of 24.1 per 100,000 among U.S. Whites (5). However, unlike clinical prostate cancer, occult prostate cancer, as determined by step sections of the prostate at autopsy, is as common among the Japanese Americans in Hawaii as among the U.S. Whites (6). This suggests the operation of factors that inhibits the progression of this tumor after induction among Japanese American men.