May 29, 2013
Vitamin C Doesn’t Significantly Improve Uric Acid Levels in Patients With Gout
Christchurch, New Zealand—While previous studies have suggested that vitamin C could moderate gout risks in patients at risk for the disease, new research found that ascorbic acid does not have a clinically significant effect in lowering uric acid levels in patients with the established disease.
The study, published in the journal Arthritis & Rheumatism, found that Vitamin C supplementation, alone or in combination with allopurinol, appears to only have a weak effect on lowering uric acid levels in gout patients.
Usual treatment for gout, which affects as many as 8.3 million Americans and can cause excruciating pain and swelling, includes medications such as allopurinol to lower urate levels by inhibiting uric acid production or probenecid to increase uric acid excretion through the kidneys.
“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,” explained lead author Prof. Lisa Stamp from the University of Otago in Christchurch, New Zealand. “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.”
Recruited for the study were 40 gout patients who had urate levels greater than the American College of Rheumatology treatment target level of 0.36 mmol/L (6 mg/100 mL). Of those, 20 patients already taking allopurinol were given an additional 500-mg 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 (500 mg/day). Blood levels of ascorbate, creatinine and uric acid were analyzed at baseline and Week 8.
Researchers determined that a modest vitamin C dose for 8 weeks did not lower urate levels to a clinically significant degree in gout patients, although it did increase ascorbate. Earlier studies had suggested that vitamin C reduced urate levels in healthy individuals without gout but with high levels of uric acid (hyperuricemia). Yet, the recent study found that reduction of uric acid was significantly less in gout patients taking vitamin C compared to those who started or increased their dose of allopurinol.
The researchers wrote in the study abstract, “Modest dose vitamin C (500mg/d) for eight weeks had no clinically significant urate lowering effect in patients with gout despite increasing plasma ascorbate. These results differ from findings in hyperuricaemic healthy controls. The uricosuric effect of modest dose vitamin C appears less in patients with gout both as monotherapy and in combination with allopurinol.”
“Though vitamin C may reduce risk of developing gout, our data does not support using vitamin C as a therapy to lower uric acid levels in patients with established gout,” Stamp concluded. “Further investigation of the urate lowering effects of a larger vitamin C dose in those with gout is warranted.”
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