Quercetin supplementation does not alter antioxidant status in humans

Abstract

This study measured the influence of ingesting quercetin on plasma measures for oxidative stress and antioxidant capacity. Male and female subjects (n = 1002) varying in age (18-85 years) and body mass index (BMI) (16.7-52.7 kg/ m2) were studied. Subjects were randomized to one of three groups using double-blinded methods: placebo, 500 mg or 1000 mg quer-cetin/day with 125 mg or 250 mg vitamin C/day, respectively. Pre-and post-study fasting blood samples show that plasma quercetin increased in a dose-responsive manner. The pattern of change in plasma F2-isoprostanes, oxidized low density lipoprotein, reduced glutathione, ferric reducing ability of plasma (FRAP) and oxygen radical absorbance capacity (ORAC) did not differ between supplementation groups or after adjustment for gender, age, BMI and disease status. In summary, quercetin supplementation over 12 weeks in doses of 500 mg or 1000 mg/day significantly increased plasma quercetin levels, but had no influence on several measures of oxidative stress and antioxidant capacity AbstractThis study measured the influence of ingesting quercetin on plasma measures for oxidative stress and antioxidant capacity. Male and female subjects (n = 1002) varying in age (18-85 years) and body mass index (BMI) (16.7-52.7 kg/m 2 ) were studied. Subjects were randomized to one of three groups using double-blinded methods: placebo, 500 mg or 1000 mg quercetin/day with 125 mg or 250 mg vitamin C/day, respectively. Pre-and post-study fasting blood samples show that plasma quercetin increased in a dose-responsive manner. The pattern of change in plasma F 2 -isoprostanes, oxidized low density lipoprotein, reduced glutathione, ferric reducing ability of plasma (FRAP) and oxygen radical absorbance capacity (ORAC) did not differ between supplementation groups or after adjustment for gender, age, BMI and disease status. In summary, quercetin supplementation over 12 weeks in doses of 500 mg or 1000 mg/day significantly increased plasma quercetin levels, but had no influence on several measures of oxidative stress and antioxidant capacity.

Effects of Quercetin Supplementation on Endurance Performance and Maximal Oxygen Consumption: A Meta-Analysis

“…Ten manuscripts (Abbey & Rankin, 2011;Bigelman et al, 2010;Cheuvront et al, 2009;Cureton et al, 2009;Davis et al, 2010;Ganio et al, 2010;MacRae & Mefferd, 2006;Nieman et al, 2009;Nieman et al, 2010 ;Quindry et al, 2008) were identified, of which seven (Bigelman et al, 2010;Cureton et al, 2009;Davis et al, 2010;Ganio et al, 2010;MacRae & Mefferd, 2006;Nieman et al, 2009;Nieman et al, 2010) met the inclusion criteria. Altogether, those manuscripts provided 10 and 4 EP and VO 2max effect estimates, respectively.…”

“…Results of human studies are somewhat less promising, showing that in healthy young subjects QS does not decrease inflammation (Nieman, Henson, Davis, Angela Murphy, et al, 2007;Nieman, Henson, Davis, Dumke, et al, 2007) and oxidative stress (McAnulty et al, 2008;Shanely et al, 2010) or improve muscle oxidative capacity (Cureton et al, 2009) and mitochondrial biogenesis (Nieman et al, 2010), but it does enhance endothelial function (Loke et al, 2008).…”

“…Several human studies evaluated quercetin's ergogenic potential on aerobic performance (Bigelman et al, 2010;Cheuvront et al, 2009;Cureton et al, 2009;Davis et al, 2010;Ganio et al, 2010;MacRae & Mefferd, 2006;Nieman et al, 2009;Nieman et al, 2010;Quindry et al, 2008), and recently its effect on endurance exercise capacity has been meta-analyzed (Kressler, MillardStafford, & Warren, 2011).…”

“…Quercetin is one of the most abundant flavonoids available to humans (Davis, Murphy, & Carmichael, 2009), is found as a nutritional supplement, is highly bioavailable (Jin et al, 2010), and is considered safe and well tolerated by humans (Bischoff, 2008;Cureton et al, 2009;Harwood et al, 2007).…”

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

“…During the study, subjects agreed to avoid any other supplements containing quercetin; no other restrictions were placed on diet, supplement usage, or medications. Several papers have recently been published from this large study, with a focus on quercetin supplementation effects on inflammation, oxidative stress, plasma quercetin response, immune function, and upper respiratory tract infections (Heinz et al 2010a(Heinz et al , 2010bJin et al 2010;Shanely et al 2010). All experimental procedures were approved by the Appalachian State University Institutional Review Board, and written informed consent was obtained from each subject.…”