Laurie Barclay, MD

March 10, 2009 — Vitamin C supplementation may help prevent gout, according to the results of a prospective study reported in the March 9 issue of the Archives of Internal Medicine.

“Several metabolic studies and a recent double-blind, placebo-controlled, randomized trial have shown that higher vitamin C intake significantly reduces serum uric acid levels,” write Hyon K. Choi, MD, DrPH, from Vancouver General Hospital and University of British Columbia in Vancouver, Canada, and colleagues. “Yet the relation with risk of gout is unknown.”

From 1986 through 2006, the investigators evaluated the association between vitamin C intake and the risk for incident gout in 46,994 male participants who had no history of gout at baseline. American College of Rheumatology criteria for gout were determined by a supplementary questionnaire, and validated questionnaires administered every 4 years examined vitamin C intake.

There were 1317 confirmed incident cases of gout during 20 years of follow-up. Compared with vitamin C intake less than 250 mg/day, the multivariate relative risk (RR) for gout associated with total vitamin C intake of 500 to 999 mg/day was 0.83 (95% confidence interval [CI], 0.71 – 0.97). For intake of 1000 to 1499 mg/day, RR was 0.66 (95% CI, 0.52 – 0.86), and for 1500 mg/day or greater, it was 0.55 (95% CI, 0.38 – 0.80; P < .001 for trend). Per 500-mg increase in total daily vitamin C intake, the multivariate RR was 0.83 (95% CI, 0.77 – 0.90).

These associations were independent of dietary and other risk factors for gout, such as body mass index, age, hypertension, diuretic use, alcohol use, and chronic renal failure, and they persisted across subgroups stratified by body mass index, alcohol use, and dairy intake.

Compared with lack of vitamin C supplementation, the multivariate RR for gout associated with supplemental vitamin C intake of 1000 to 1499 mg/day was 0.66 (95% CI, 0.49 – 0.88), and it was 0.55 (95% CI, 0.36 – 0.86) for 1500 mg/day or greater (P < .001 for trend).

“Higher vitamin C intake is independently associated with a lower risk of gout,” the study authors write. “Supplemental vitamin C intake may be beneficial in the prevention of gout.”

Limitations of this study include dietary consumption self-reported by questionnaire; observational design; lack of confirmation of gout diagnosis by observation of urate crystals in joint fluid; and restriction to health professionals, limiting generalizability.

The National Institutes of Health and TAP Pharmaceuticals supported this study in part. The study authors have disclosed no relevant financial relationships.

Arch Intern Med. 2009;169:502-507.

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