March 16, 2009

Vitamin C May Reduce Risk of Gout

Image of multicolored crystals The uric acid crystals that cause gout. Wellcome Images.

A new study has linked higher vitamin C intake with a lower risk of gout. Vitamin C supplements, the results imply, may help to prevent gout.

Nearly 3 million adults nationwide are estimated to have gout. The condition develops when excess uric acid in the blood begins to form crystals. These crystals then accumulate in joints to cause swelling and pain. Gout often first affects the joints of the big toe, but many other joints can also be involved. Left untreated over time, gout can permanently damage affected joints.

Recent studies have found that higher vitamin C intake reduces uric acid levels in blood. Whether this ultimately affects the risk of gout, however, has been unknown. A research team led by Dr. Hyon K. Choi of the University of British Columbia (now at the Boston University School of Medicine) set out to examine the relationship between vitamin C intake and gout. Their work was supported by grants from several NIH institutes and TAP Pharmaceuticals.

The researchers studied data gathered between 1986 and 2006 by the ongoing Health Professionals Follow-up Study. The study asked male health professionals to fill out a dietary questionnaire every 4 years. From these, the researchers calculated the men’s vitamin C intake, adding in vitamin C from supplements. Every 2 years, the men also recorded whether they had received a doctor’s diagnosis of gout. The researchers were thus able to compare vitamin C intake with the incidence of gout in almost 47,000 men who didn’t have gout when the study began.

By 2006, gout had developed in 1,317 of the men. The results, published in the March 9, 2009, issue of Archives of Internal Medicine, showed that men who had the highest vitamin C intake—1,500 milligrams or higher per day—had a 45% lower risk of gout than those with the lowest daily intake—less than 250 milligrams per day.

When the researchers focused on vitamin C supplements, they found that the men who took 1,000-1,499 milligrams per day had a 34% lower risk of gout than men who didn’t take any vitamin C supplements. Those who took 1,500 milligrams per day had a 45% lower risk than those who didn’t take any.

These associations held independent of dietary and other known risk factors for gout, including body mass index (a ratio of weight to height), age, hypertension, diuretic use, alcohol use and chronic renal failure. The results support the idea that vitamin C has a protective effect against gout. The researchers believe it may act by helping the kidneys clear uric acid from blood. The vitamin might also help protect against the inflammation caused by gout.

The protective effect of vitamin C against gout still needs to be confirmed in a controlled clinical trial. The recommended daily intake for vitamin C, set by the Food and Nutrition Board at the National Academies’ Institute of Medicine, is currently 90 milligrams per day for men. High doses of vitamin C can cause side effects, including stomach upset and diarrhea, so talk to your doctor if you’re considering taking vitamin C supplements to prevent gout.

—by Harrison Wein, Ph.D.

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