Despite previous studies touting its benefit in moderating gout risk, new research reveals that vitamin C, also known ascorbic acid, does not reduce uric acid (urate) levels to a clinically significant degree in patients with established gout.

Vitamin C supplementation, alone or in combination with allopurinol, appears to have a weak effect on lowering uric acid levels in gout patients according to the results published in the American College of Rheumatology (ACR) journal, Arthritis & Rheumatism.

Gout is an inflammatory arthritis that causes excruciating pain and swelling triggered by the crystallisation of uric acid within the joints. Medical evidence reports that long-term gout management requires treatment with medications that lower urate levels by inhibiting uric acid production (allopurinol) or increasing uric acid excretion (probenecid) through the kidneys.

Lead author Professor Lisa Stamp, from the University of Otago in Christchurch, New Zealand, said: "While current treatments are successful in reducing the amount of uric acid in the blood, there are many patients who fail to reach appropriate urate levels and need additional therapies. Vitamin supplementation is one such alternative therapy and the focus of our current study, which looked at the effects of vitamin C on urate levels in patients with gout."

The team recruited gout patients who had urate levels greater than the ACR treatment target level of 0.36mmol/L (6mg/100 mL). Of the 40 participants with gout, 20 patients already taking allopurinol were given an additional 500mg dose of vitamin C daily or had the dose of allopurinol increased, while another 20 patients not already taking allopurinol were either started on allopurinol or vitamin C (500mg/day). Researchers analysed blood levels of vitamin C (ascorbate), creatinine and uric acid at baseline and week eight.