Intake of flavonoids has been inversely related to the risk of various common neoplasms, but limited data exist on renal cell carcinoma (RCC). We used data from a case-control study conducted between 1994 and 2002 in four Italian areas to study the relation between major flavonoid classes and RCC. The study included 767 cases with incident, histologically confirmed RCC and 1,534 hospital controls admitted for acute, nonneoplastic conditions and matched with cases by study center, sex, and quinquennia of age. We applied published data on food and beverage content of six major classes of flavonoids to dietary information collected through a validated food frequency questionnaire. After adjustment for major recognized confounding factors and total energy intake, the odds ratios for subjects in the highest versus the lowest quintile of intake were 0.80 [95% confidence interval (95% CI), 0.58-1.11] for total flavonoids, 0.76 (95% CI, 0.56-1.03) for isoflavones, 0.94 (95% CI, 0.60-1.47) for anthocyanidins, 0.77 (95% CI, 0.56-1.06) for flavan-3-ols, 0.90 (95% CI, 0.67-1.21) for flavanones, 0.68 (95% CI, 0.50-0.93) for flavones, and 0.69 (95% CI, 0.50-0.95) for flavonols. Allowance for vegetable and fruit consumption only partly explained these inverse relations. Thus, flavonoids, and particularly flavones and flavonols, may account, at least in part, for the favorable role of plant foods on RCC.
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