Daily Quercetin Supplementation Dose-Dependently Increases Plasma Quercetin Concentrations in Healthy Humans

Abstract

Our aim was to investigate the effects of an oral supplementation of quercetin at 3 different doses on plasma concentrations of quercetin, parameters of oxidant/antioxidant status, inflammation, and metabolism. To this end, 35 healthy volunteers were randomly assigned to take 50, 100, or 150 mg/d (group Q50-Q150) quercetin for 2 wk. Fasting blood samples were collected at the beginning and end of the supplementation period. Compared with baseline, quercetin supplementation significantly increased plasma concentrations of quercetin by 178% (Q50), 359% (Q100), and 570% (Q150; P , 0.01 for all).High interindividual variation was found for plasma quercetin concentrations (36-57%). Quercetin did not affect concentrations of serum uric acid or plasma a-and g-tocopherols, oxidized LDL, and tumor necrosis factor-a, or plasma antioxidative capacity as assessed by the ferric-reducing antioxidant potential and oxygen radical absorbance capacity assays. In addition,

Enriched cereal bars are more effective in increasing plasma quercetin compared with quercetin from powder-filled hard capsules

“…This finding is in accordance with our previous human kinetic study (15) and has also been found in pigs (27,28) . However, in contrast to mice and rats, in which nearly one-half of the absorbed amount of quercetin is methylated to isorhamnetin (29 -32) , the proportion of the methylated derivatives in human and pig plasma is rather low (approximately 15 -20 % of total plasma flavonols).…”

“…The plasma profiles of quercetin after the ingestion of 130 mg quercetin from capsules were similar to our previous human study that investigated the kinetics of plasma quercetin from three different quercetin dosages (50, 100 and 150 mg quercetin dihydrate) (15) . In accordance with previous human studies, we observed a relatively high inter-individual variance in plasma concentration -time curves of quercetin, isorhamnetin and tamarixetin following supplementation with quercetin (15 -18) , although our non-smoking female study population was very homogenous with respect to age, baseline plasma quercetin concentrations, body weight, BMI, fat mass and fat-free mass as well as lifestyle and physical activity.…”

Quercetin with vitamin C and niacin does not affect body mass or composition

“…In separate studies, no differences in body mass were detected after supplementation with quercetin in rats fed either high-fat or high-fat-high-sucrose chow (Barrenetxe et al 2006;Yamamoto and Oue 2006). Similar to our findings, Egert et al (2008) showed that low doses of quercetin supplements (50, 100, and 150 mg·day -1 ) for 2 weeks did not alter body mass or percent body fat in healthy human subjects. In addition, in a subset of subjects, quercetin failed to alter resting energy expenditure (Egert et al 2008).…”

“…The obesity pandemic has accelerated cell, animal, and human research on the anti-obesity effects of flavonoids (Borchardt and Huber 1975;Melzig 1996;Hase et al 2001;Nagao et al 2001Nagao et al , 2005Nagao et al , 2007Singh et al 2003;Alexander 2006;Greenberg et al 2006;Harwood et al 2007;Bose et al 2008;Egert et al 2008;Ito et al 2008;Stewart et al 2008;Liu et al 2009;Faria et al 2010;Grove and Lambert 2010;Zhu et al 2010). For example, several animal studies indicate that 3-15 weeks of supplementation with green tea extract and epigallocatechin gallate (EGCG) reduce body mass and fat mass (Bose et al 2008;Ito et al 2008).…”

“…In one study, mice fed a high-fat diet with quercetin supplements exhibited transiently increased energy expenditure after 3 weeks and decreased inflammatory markers, but without measurable effects on body mass or fat mass (Stewart et al 2008). One small-scale human study reported no effects of 2-week, low-dose quercetin supplementation (50, 100, or 150 mg·day -1 ) on body mass or body composition in healthy subjects (Egert et al 2008).…”