Soy and Isoflavone Intake Are Associated With Reduced Risk of Ovarian Cancer in Southeast China

To investigate whether intake of soy and isoflavones has an inverse association with ovarian cancer risk, a case-control study was conducted in Hangzhou, China. Cases were 254 patients with histologically confirmed epithelial ovarian cancer. The 652 controls comprised 340 hospital visitors, 261 non-neoplastic hospital outpatients, and 51 women recruited from the community. Habitual dietary intakes including 9 soy foods were measured by face-to-face interview using a validated and reliable food-frequency questionnaire. Unconditional logistic regression analyses were used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) accounting for age, demographic characteristics, hormonal factors, and total energy intake. Intake of soy and isoflavones was inversely related to the risk of ovarian cancer. Compared with the highest versus the lowest quartile intake, the ORs were 0.50 (95% CI = 0.31-0.82) for total soy foods and 0.51 (95% CI = 0.31-0.85) for isoflavones. Among subgroups of soy foods and isoflavones, the ORs for soybeans, bean curd, daidzein, genistein, and glycitein were 0.35 (95% CI = 0.22-0.58), 0.49 (95% CI = 0.29-0.81), 0.52 (95% CI = 0.31-0.87), 0.50 (95% CI = 0.30-0.84), and 0.59 (95% CI = 0.35-0.97), respectively.