LIVERPOOL, ENGLAND — Consumption of soft drinks containing fructose may underlie the sharp increase in gout in American adults that has occurred in recent decades, Dr. Hyon K. Choi said at the annual meeting of the British Society for Rheumatology.
Since 1967, when high-fructose corn syrup became commercially available and began to be used for sweetening soft drinks, there has been a 61% increase in the consumption of these beverages and a doubling of the incidence and prevalence of gout, particularly in men.
Conventional strategies for the prevention of gout have emphasized limiting consumption of purine-rich foods because uric acid is a breakdown product of purine. But fructose also can increase uric acid. The process involves the breakdown of adenosine triphosphate to adenosine monophosphate, a uric acid precursor, said Dr. Choi, a rheumatologist at the University of British Columbia, Vancouver.
Fructose also contributes to impaired glucose tolerance and increases insulin resistance and hyperinsulinemia, which could elevate serum uric acid levels.
Prospective studies have shown that sugary soft drinks contribute significantly to gout—as well as obesity, type 2 diabetes, and metabolic syndrome, he said.
In the large, ongoing health-professionals follow-up study of more than 51,000 men aged 40–75 years who answered dietary questionnaires and have been followed since 1986, a total of 755 new cases of gout have been diagnosed. The multivariate relative risk of gout for five to six servings of sugary soft drinks a week was 1.29; this rose to 1.85 for two or more servings a day, representing an 85% increase in incident gout in the highest consumers (BMJ 2008;336:309–12).
In another study that includes 14,761 participants aged 20 years and older from the third National Health and Nutrition Examination Survey (NHANES-III), serum uric-acid levels increased significantly with increasing sugary soft-drink consumption, with multivariate odds ratios for hyperuricemia being 1.82 in those who consumed four or more servings a day (Arthritis Rheum. 2008;59:109–16).
In both of these studies, the associations were independent of risk factors for gout including alcohol use, hypertension, and body mass index.
Data from NHANES-III, which is considered a nationally representative sample, also suggest that coffee may be protective, but only if it is drunk in large quantities, he said. After adjustment for age and sex, serum uric-acid levels in those drinking six cups of coffee a day were significantly lower by 0.43 mg/dL than in those who did not drink coffee (Arthritis Rheum. 2007;57:816–21).
The effect was not related to caffeine intake, as modest effects were seen with decaffeinated coffee, and none were seen in tea drinkers. “It could derive from other components in coffee such as chlorogenic acid or noncaffeine xanthines,” he said.
In conclusion, patients at risk for gout should continue to emphasize limitations on purine-rich foods such as beer and certain meats. Purine-rich vegetables such as spinach and beans do not seem to elevate uric-acid levels, and need not be avoided.
Sugary soft drinks and other processed foods containing fructose should be avoided, not only for gout prevention but for prevention of the common comorbidities such as hypertension and obesity, he said.
Dr. Choi's work has been funded by the National Institutes of Health and the Arthritis Society of Canada. He said he has served on the advisory boards for TAP Pharmaceutical Products Inc. and Savient Pharmaceuticals Inc.