Quercetin lowers plasma uric acid in pre-hyperuricaemic males: a randomised, double-blinded, placebo-controlled, cross-over trial
What this study found
Quercetin lowered plasma uric acid after 4 weeks and was well tolerated. In the quercetin period, plasma uric acid fell from 330 (56) µmol/l at baseline to 304 (48) µmol/l at 4 weeks, with a mean change of -26•5 (95% CI -7•6, -45•5; P = 0•008); the 2-week change was -15•9 (95% CI 0•9, -32•8; P = 0•06). Placebo did not produce a significant change: 315 (45) to 320 (47) µmol/l at 4 weeks (P = 0•60). Quercetin did not significantly affect fasting glucose, 24-hour urinary uric acid excretion, or systolic blood pressure, and no adverse events were reported.
- Study & population
- For the quercetin arm, 22 healthy adult men were studied in a randomised, double-blind, placebo-controlled, cross-over trial.
- Intervention
- Quercetin was given orally as quercetin dihydrate tablets at 500 mg daily for 4 weeks.
- Key limitation
- The trial was small and included only healthy men, limiting generalizability to women, patients with gout, or broader clinical populations.
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Open PDFOriginal abstract
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.