Effects of daily quercetin-rich supplementation on cardiometabolic risks in male smokers

Limited information from human studies indicates that dietary quercetin supplementation influences blood lipid profiles, glycemic response, and inflammatory status, collectively termed cardiometabolic risks. We tested the hypothesis that quercetin-rich supplementation, derived from onion peel extract, improves cardiometabolic risk components in healthy male smokers in a randomized, double blinded, placebo-controlled parallel design. Randomly assigned subjects were instructed to take either the placebo (n = 43) or 100 mg quercetin capsules each day (n = 49) for 10 weeks. Anthropometric parameters and blood pressure were measured, and blood lipids, glucose, interleukin-6, and soluble vascular cell adhesion molecule-1 (sVCAM-1) were determined at baseline and after 10 weeks of quercetin supplementation. Quercetin-rich supplementation significantly reduced serum concentrations of total cholesterol (P < 0.05) and LDL-cholesterol (P < 0.01), whereas these effects were not shown in the placebo group. Furthermore, significant increases were observed in serum concentrations of HDL-cholesterol both in the placebo (P < 0.005) and quercetin-rich supplementation group (P < 0.001); however, changes in HDL-cholesterol were significantly greater in subjects receiving quercetin-rich supplementation than the placebo. Both systolic (P < 0.05) and diastolic blood pressure (P < 0.01) decreased significantly in the quercetin-rich supplementation group. Glucose concentrations decreased significantly after 10 weeks of quercetin-rich supplementation (P < 0.05). In contrast, no effects of quercetin-rich supplementation were observed for the inflammatory markers-IL-6 and sVCAM-1. Daily quercetin-rich supplementation from onion peel extract improved blood lipid profiles, glucose, and blood pressure, suggesting a beneficial role for quercetin as a preventive measure against cardiovascular risk.