Quercetin lowers plasma uric acid in pre-hyperuricaemic males: a randomised, double-blinded, placebo-controlled, cross-over trial

For the quercetin arm, 22 healthy adult men were studied in a randomised, double-blind, placebo-controlled, cross-over trial. Participants were aged 19 to 65 years, non-smokers, not heavy drinkers, and had non-optimal/high-normal plasma uric acid without gout or kidney stones; the study was conducted at the University of Leeds, UK, from February 2013 to April 2014.

Quercetin was given orally as quercetin dihydrate tablets at 500 mg daily for 4 weeks. The active tablet contained 544 (SD 45) mg quercetin dihydrate aglycone per tablet and was compared with placebo in a randomised, double-blind, cross-over design with a 4-week washout between periods.

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.

The trial was small and included only healthy men, limiting generalizability to women, patients with gout, or broader clinical populations. The intervention was short term and used a cross-over design, so it does not address durability of effect or long-term safety. Dietary intake and lifestyle were generally maintained but not comprehensively characterized, which may leave residual confounding.