Consumption of black currants, lingonberries and bilberries increases serum quercetin concentrations

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Abstract
Objective: To study serum quercetin concentrations of subjects consuming berries or habitual Finnish diets. Design: Randomized parallel dietary intervention. Subjects: Forty healthy men (age 60 y). Intervention: Twenty subjects consumed 100 g/day of berries (black currants, lingonberries and bilberries) for 8 weeks. Twenty subjects consuming their habitual diets served as controls. Fasting blood samples were obtained 2 weeks prior to the study, at baseline, and at 2, 4 and 8 weeks. Intake of quercetin was assessed from 3 day food records collected at baseline and at 8 weeks. Results: The serum quercetin concentrations were significantly higher in the subjects consuming berries compared to the control group (P=0.039 ANCOVA with repeated measures). During the berry consumption period the mean serum concentrations of quercetin ranged between 21.4 and 25.3 µg/l in the berry group, which was 32–51% higher compared with the control group. According to 3 day food records, there was no difference in quercetin intake at baseline, but at 8 weeks the intake was 12.3±1.4 mg/day (mean±s.e.m.) in the berry group and 5.8±0.6 mg/day in the control group (P=0.001). Conclusion: The results indicate that the berries used in this study are a good source of bioavailable quercetin. Sponsorship: The study was supported by the Academy of Finland, Juho Vainio Foundation and the Finnish Foundation for Cardiovascular Research.