Lack of effect of tart cherry concentrate dose on serum urate in people with gout

Stamp LK, Chapman P, Frampton C, Duffull SB, Drake J, Zhang Y, Neogi T · Rheumatology (Oxford)

A dose-ranging trial run by two of the authors of the positive case-crossover study. It found no effect of dose on serum-urate area under the curve, on urine urate excretion, on urinary anthocyanin, or on flare frequency (p = 0.76), and no change to allopurinol's own urate lowering. Twenty-four adverse events were reported, one (hyperglycaemia) possibly related. The authors conclude that if cherry concentrate does reduce flares over a longer period, urate lowering is not how.

Population

Adults with gout and serum urate > 0.36 mmol/L, half on allopurinol

Intervention

Tart cherry juice concentrate at 7.5, 15, 22.5 or 30 mL twice daily for 28 days

Comparator

Placebo

Limitations

n=50 across five arms, so roughly ten people per dose, and 28 days with no formal power calculation. Open-label: participants prepared the doses at home and the placebo was two drops of concentrate in water. Underpowered for flares by design. Funded by the Health Research Council of New Zealand. Registered ANZCTR 12615000741583.