The relationship between fasting plasma concentrations of selected flavonoids and their ordinary dietary intake

Abstract

Epidemiological studies suggest that a diet high in flavonoids protects against chronic diseases such as CVD and cancer. The objective of the present study was to evaluate the relationship between the intake of quercetin, kaempferol, isorhamnetin, apigenin and luteolin and their corresponding plasma concentrations, and further to explore whether these flavonoids can serve as biomarkers of their intake. Flavonoid intake and their plasma concentrations were analysed in ninety-two subjects consuming their habitual diet. Flavonoid intake was estimated with 7-d dietary records using available data on the flavonoid content of food. Plasma flavonoid concentrations were quantified by HPLC. In addition, we undertook a dietary intervention study to investigate plasma apigenin concentration after the consumption of celery leaf. The mean intake estimates of quercetin, kaempferol, isorhamnetin, apigenin and luteolin amounted to 1358, 1497, 1231, 423 and 808mg/d, respectively. The corresponding mean plasma concentrations were 8023, 5786, 3994, 1062 and 9990nmol/l. The mean 7d intake of five flavonoids was positively correlated to their corresponding plasma concentrations, with correlation coefficients ranging from 033 to 051 (P<005). In the dietary intervention study, the plasma apigenin concentration rose after celery leaf ingestion, and fell within 28h to below the limit of detection (232nmol/l). The present results suggest that quercetin, kaempferol, isorhamnetin, apigenin and luteolin are bioavailable from the diet. The levels of fasting plasma flavonoids seem to be suitable biomarkers of short-term intake. The combination of plasma flavonoids with their intake may prove useful when the possible health-protective effects of flavonoids are studied. © 2009 The Authors.