title: Quercetin lowers plasma uric acid in pre-hyperuricaemic males: a randomised, double-blinded, placebo-controlled, cross-over trial.
abstract: Elevated plasma uric acid concentration is a risk factor for gout, insulin resistance and type 2 diabetes. Quercetin, a flavonoid found in high levels in onions, tea and apples, inhibits xanthine oxidoreductase in vitro, the final step in intracellular uric acid production, indicating that quercetin might be able to lower blood uric acid in humans. We determined the effects of 4 weeks of oral supplementation of quercetin on plasma uric acid, blood pressure and fasting glucose. This randomised, double-blinded, placebo-controlled, cross-over trial recruited twenty-two healthy males (19-60 years) with baseline plasma uric acid concentration in the higher, but still considered healthy, range (339 (SD 51) µmol/l). The intervention included one tablet containing 500 mg quercetin daily for 4 weeks, compared with placebo, with a 4-week washout period between treatments. The primary outcome was change in concentrations of plasma uric acid after 2 and 4 weeks; secondary outcome measures were changes in fasting plasma glucose, 24-h urinary excretion of uric acid and resting blood pressure. After quercetin treatment, plasma uric acid concentrations were significantly lowered by -26·5 µmol/l (95% CI, -7·6, -45·5; P=0·008), without affecting fasting glucose, urinary excretion of uric acid or blood pressure. Daily supplementation of 500 mg quercetin, containing the bioavailable amount of quercetin as present in approximately 100 g red onions, for 4 weeks, significantly reduces elevated plasma uric acid concentrations in healthy males.
authors.affiliation: School of Food Science and Nutrition,University of Leeds,Leeds LS2 9JT,UK.
authors.forename: Yuanlu
authors.initials: Y
authors.lastname: Shi
authors.affiliation: School of Food Science and Nutrition,University of Leeds,Leeds LS2 9JT,UK.
authors.forename: Gary
authors.initials: G
authors.lastname: Williamson
mesh_terms: D000328:Adult; D001786:Blood Glucose / Q000378:metabolism; D001794:Blood Pressure / Q000187:drug effects; D015992:Body Mass Index; D018592:Cross-Over Studies; D003924:Diabetes Mellitus, Type 2 / Q000097:blood; D019587:Dietary Supplements; D004311:Double-Blind Method; D006801:Humans; D033461:Hyperuricemia / Q000188:drug therapy*; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance; D008297:Male; D008875:Middle Aged; D011794:Quercetin / Q000494:pharmacology*; D016896:Treatment Outcome; D014527:Uric Acid / Q000097:blood* / Q000652:urine; D055815:Young Adult
chemical_list: D001786:Blood Glucose; D007328:Insulin; D014527:Uric Acid; D011794:Quercetin
keywords: Blood pressure; Clinical trials; Fasting glucose; Hyperuricaemia; Quercetin; Uric acid