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Quercetin supplementation does not alter antioxidant status in humans
R Andrew Shanely1, Amy M Knab, David C Nieman
1North Carolina Research Campus, Appalachian State University, Human Performance Laboratory, Plants for Human Health Building, 600 Laureate Way, Kannapolis, NC 28081, USA. shanelyra@appstate.edu
Free Radical Research
|December 2, 2009
Summary
Quercetin supplements increased plasma quercetin levels in adults. However, this flavonoid did not impact measures of oxidative stress or antioxidant capacity in this 12-week study.
Area of Science:
- Nutritional Science
- Biochemistry
- Human Physiology
Background:
- Oxidative stress is implicated in numerous chronic diseases.
- Quercetin, a dietary flavonoid, possesses antioxidant properties in vitro.
- The in vivo efficacy of quercetin for oxidative stress markers requires further investigation.
Purpose of the Study:
- To evaluate the impact of quercetin supplementation on plasma oxidative stress and antioxidant capacity markers.
- To determine if quercetin's effects are dose-dependent and influenced by demographic factors.
Main Methods:
- A double-blind, randomized controlled trial involving 1002 adult participants.
- Supplementation groups received placebo, 500 mg quercetin + 125 mg vitamin C, or 1000 mg quercetin + 250 mg vitamin C daily for 12 weeks.
- Plasma levels of quercetin, F(2)-isoprostanes, oxidized LDL, reduced glutathione, FRAP, and ORAC were measured pre- and post-study.
Main Results:
- Plasma quercetin levels increased significantly and in a dose-responsive manner with supplementation.
- No significant differences were observed in F(2)-isoprostanes, oxidized LDL, reduced glutathione, FRAP, or ORAC between groups.
- Adjustments for gender, age, BMI, and disease status did not alter these findings.
Conclusions:
- Quercetin supplementation effectively increases plasma quercetin concentrations.
- This study found no evidence that quercetin supplementation influences key markers of oxidative stress or antioxidant capacity in humans.
- Further research may be needed to explore alternative dosages, durations, or specific populations.
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