The Effects of Vitamin C Supplementation on Serum Concentrations of Uric Acid

Results of a Randomized Controlled Trial

Huang, Han-Yao PhD
Appel, Lawrence J. MD
Choi, Michael J. MD
Gelber, Allan C. MD, PhD
Charleston, Jeanne RN
Norkus, Edward P. PhD
Miller, Edgar R. III MD, PhD

¹Johns Hopkins University, Baltimore, Maryland
²Our Lady of Mercy Medical Center, Bronx, New York

Address correspondence and reprint requests to Han-Yao Huang, PhD, Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, 615 N. Wolfe Street, E-6144, Baltimore, MD 21205-2223. E-mail: [email protected].

Supported by the NIH (grant RR-00722 from the National Center for Research Resources).

Submitted for publication October 04, 2004; accepted in revised form March 14, 2005

Arthritis & Rheumatism 52(6):p 1843-1847, June 2005.

Objective

Reductions in serum uric acid levels are clinically relevant. Previous studies have suggested a uricosuric effect of vitamin C. Whether vitamin C reduces serum uric acid is unknown. We undertook this study to determine the effects of vitamin C supplementation on serum uric acid concentrations.

Methods

The study was a double-blinded placebo-controlled randomized trial conducted in research units affiliated with an academic institution. Study participants were 184 nonsmokers, randomized to take either placebo or vitamin C supplements (500 mg/day) for 2 months.

Results

At the end of the study period, serum uric acid levels were significantly reduced in the vitamin C group (mean change −0.5 mg/dl [95% confidence interval −0.6, −0.3]), but not in the placebo group (mean change 0.09 mg/dl [95% confidence interval −0.05, 0.2]) (P < 0.0001). The same pattern of results was evident in subgroups defined by age, sex, race, body mass index, chronic illness, diuretic use, and quartiles of baseline serum ascorbic acid levels. In the subgroups, from the lowest to the highest quartile of baseline serum uric acid, net mean changes (95% confidence intervals) in serum uric acid with vitamin C supplementation were −0.4 (−0.8, 0.01), −0.5 (−0.9, −0.2), −0.5 (−0.8, −0.2), and −1.0 (−1.6, −0.4) mg/dl (P = 0.06, 0.005, 0.003, and 0.002, respectively). Compared with placebo, vitamin C increased the estimated glomerular filtration rate.

Conclusion

Supplementation with 500 mg/day of vitamin C for 2 months reduces serum uric acid, suggesting that vitamin C might be beneficial in the prevention and management of gout and other urate-related diseases.