Intakes of anthocyanins and flavones are associated with biomarkers of insulin resistance and inflammation in women

Although laboratory data suggest that several flavonoid subclasses are involved in glucose metabolism, limited clinical and epidemiologic data are available. The current study examined associations between habitual intake of flavonoid subclasses, insulin resistance, and related inflammatory biomarkers. In a cross-sectional study of 1997 females aged 18-76 y, intakes of total flavonoids and their subclasses (flavanones, anthocyanins, flavan-3-ols, polymeric flavonoids, flavonols, flavones) were calculated from food frequency questionnaires using an extended USDA database. Fasting serum glucose, insulin, high-sensitivity C-reactive protein (hs-CRP; n = 1432), plasminogen activator inhibitor-1 (n = 843), and adiponectin (n = 1452) levels were measured. In multivariable analyses, higher anthocyanin and flavone intake were associated with significantly lower peripheral insulin resistance [homeostasis model assessment of insulin resistance; quintile 5 (Q5) to Q1 = -0.1, P-trend = 0.04 for anthocyanins and flavones] as a result of a decrease in insulin concentrations (Q5-Q1 = -0.7 μU/mL, P-trend = 0.02 anthocyanins; Q5-Q1 = -0.5 μU/mL, P-trend = 0.02 flavones). Higher anthocyanin intake was also associated with lower hs-CRP levels (Q5-Q1 = -0.3 mg/L, P-trend = 0.04), whereas those in the highest quintile of flavone intake had improved adiponectin levels (Q5-Q1 = 0.7 μg/L, P-trend = 0.01). Anthocyanin-rich foods were also associated with lower insulin and inflammation levels. No significant associations were observed for total or other flavonoid subclasses. Higher intakes of both anthocyanins and flavones were associated with improvements in insulin resistance and hs-CRP. These associations were found with intakes readily achieved in the diet. The observed reduction in insulin levels was similar to that reported previously for other lifestyle factors. Dose-response trials are needed to ascertain optimal intakes for the potential reduction of type 2 diabetes risk.