Flavonoids and prostate cancer risk: a study in Italy.

Flavonoids have been associated with a reduced risk of lung, digestive tract, and certain hormone-related cancers. With reference to prostate cancer, a few epidemiological studies have found an inverse relation with intake of isoflavones, flavonols, and flavones, although the evidence remains limited and inconsistent. The role of six principal classes of flavonoids on prostate cancer was investigated using data from a multicentric case-control study conducted between 1991 and 2002 in Italy. This included 1,294 incident, histologically confirmed carcinomas of the prostate and 1,451 controls admitted to the same hospitals as cases for a wide spectrum of acute, non-neoplastic conditions. The patients' usual diet was assessed using a validated and reproducible food-frequency questionnaire; food and beverage content of six major classes of flavonoids was obtained from the U.S. Department of Agriculture. No association between prostate cancer risk was found with any of the flavonoids analyzed: the multivariate odds ratios for the highest versus the lowest quintile of intake were 0.96 (95% confidence interval, CI = 0.75-1.23) for flavanones, 1.3 (95% CI = 1.01-1.69) for flavan-3-ols, 1.23 (95% CI = 0.95-1.61) for flavonols, 1.09 (95% CI = 0.85-1.40) for flavonols, 1.18 (95% CI = 0.91-1.53) for anthocyanidins, 0.98 (95% CI = 0.76-1.26) for isoflavones, and 1.20 (95% CI = 0.92-1.58) for total flavonoids, all nonstatistically significant. Thus, the results of the present study do not support a protective effect of flavonoids on prostate cancer in this Italian population, characterized by a high intake of flavonoid-containing foods (except isoflavone-rich foods).