Estimated dietary flavonoid intake and major food sources of U.S. adults.

Estimating flavonoid intake is a first step toward documenting the protective effects of flavonoids against risk of chronic diseases. Although flavonoids are important dietary sources of antioxidants, insufficient data on the comprehensive food composition of flavonoids have delayed the assessment of dietary intake in a population. We aimed to estimate the dietary flavonoid intake in U.S. adults and its sociodemographic subgroups and to document major dietary sources of flavonoids. We expanded the recently released USDA Flavonoid Database to increase its correspondence with the 24-h dietary recall (DR) of the NHANES 1999-2002. We systematically assigned a particular food code to all foods that were prepared or processed similarly. This expanded database included 87% of fruits and fruit juices, 86% of vegetables, 75% of legumes, and, overall, 45% of all foods reported by the 24-h DR of the NHANES 1999-2002. Estimated mean daily total flavonoid intake, 189.7 mg/d, was mainly from flavan-3-ols (83.5%), followed by flavanones (7.6%), flavonols (6.8%), anthocyanidins (1.6%), flavones (0.8%), and isoflavones (0.6%). The flavonoid density of diets increased with age (P < 0.001) and income (P < 0.05). It was higher in women (P < 0.001), Caucasians (P < 0.001), and vitamin supplement users (P < 0.001) and lower in adults with high levels of nonleisure time physical activity (P < 0.01) compared with their counterparts. The greatest daily mean intake of flavonoids was from the following foods: tea (157 mg), citrus fruit juices (8 mg), wine (4 mg), and citrus fruits (3 mg). The proposed relation between flavonoid intake and the prevention of chronic diseases needs further investigation using the estimates introduced in this study.