1. ¹Biomarker Laboratory, National Public Health Institute, Helsinki, Finland
2. ²Research and Development Centre, The Social Insurance Institution, Turku, Finland
3. ³Research Unit of Substance Abuse, National Public Health Institute, Helsinki, Finland

Correspondence: I Erlund, Biomarker Laboratory, National Public Health Institute (KTL), Mannerheimint. 166, 00300 Helsinki, Finland. E-mail: iris.erlund@ktl.fi

^*Guarantors: AA and JM

^†Contributors: IE performed quercetin analyses, interpreted the data and wrote the article. PH and JM designed and executed the dietary intervention. PH calculated quercetin intake. EM performed statistical analyses. GA and AA supervised quercetin analyses. All authors read and commented on the manuscript.

Received 9 October 2001; Revised 17 April 2002; Accepted 18 April 2002.

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 g/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 12.31.4 mg/day (means.e.m.) in the berry group and 5.80.6 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.