Vitamin C may reduce uric acid, with one meta-analysis of 12 clinical trials[1] reporting a reduction of 0.35 mg/dL in uric acid with supplemental vitamin C. However, the included studies had highly variable designs and populations. For example, many studies were performed on people performing moderate[2][3] to high levels of exercise,[4][5] including one study on ultramarathon runners.[6] Results from these studies may not be applicable to most people at risk of gout. Only one randomized trial[7] has investigated the effect of vitamin C on people with gout, but it compared vitamin C to a well established uric acid-lowering drug (allopurinol) rather than a placebo. This study reported a greater reduction in uric acid with allopurinol compared to 500 mg vitamin C and no reduction in uric with vitamin C compared to baseline. One large clinical trial on middle men observed a decrease in the risk of gout with supplementation, though there was no clear benefit among men with a BMI of 30 or higher.[8] There are currently no randomized, placebo-controlled trials examining the effect of vitamin C among people with active gout.
Tart cherries have been suggested to lower uric acid, though findings from clinical trials have been mixed. In one study on women who did not have gout, consumption of tart cherry juice led to a 19.2% reduction in uric acid compared to a sugar matched placebo,[9] whereas in a study on people with gout, consumption of various doses of tart cherry juice had no effect on uric acid levels or gout flares.[10]
A limited number of trials have reported reductions in uric acid from various supplements, including phytic acid (aka inositol hexametaphosphate or IP6),[11] a combination of glycine and tryptophan[12], psyllium fiber,[13] and probiotics.[14]