Huang HY, et al. The effects of vitamin C supplementation on serum concentrations of uric acid: results of a randomized controlled trial. Arthritis Rheum 2005;52:1843-1847.

One hundred eighty-four nonsmoking volunteers (mean age, 58 years) were randomly assigned to receive, in double-blind fashion, one of the following for two months: 1) vitamin C 500 (mg/day), 2) vitamin E (RRR-alpha-tocopheryl acetate, 400 IU/day), 3) both supplements, or 4) placebo. The mean fasting serum uric acid concentration decreased (-0.5 mg/dl) in the vitamin C groups and increased (+0.09 mg/dl) in the no-vitamin-C groups (p < 0.0001 for the difference in the change between groups). Among the 21 participants with hyperuricemia (serum uric acid level greater than 7 mg/dl) at baseline who received vitamin C, the mean serum uric acid concentration decreased by 1.5 mg/dl (p = 0.0008). Vitamin E had no effect on serum uric acid concentrations.

Comment: Lowering serum uric acid levels is useful for the prevention and management of gout. As hyperuricemia is also an independent cardiovascular disease risk factor, reducing serum uric acid levels may be one of the many mechanisms whereby vitamin C enhances heart health. The results of the present study indicate that supplementation with 500 mg/day of vitamin C for two months produced a modest reduction in serum uric acid levels. Previous research suggested that this effect is due to an increase in urinary excretion of uric acid.

The uric acid-lowering effect of vitamin C was reported as early as 1976, but doses of 8 g/day were used and the supplementation period lasted only one week. The new study indicates that considerably smaller doses, when taken over a longer period of time, can also lower uric acid levels.