At the annual meeting of the British Society for Rheumatology it was said that consumption of soft drinks containing fructose may underlie the sharp increase in gout among American adults that has occurred in recent decades.
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. Since that time, there also has been a doubling of the incidence and prevalence of gout, particularly among men. Approximately 6 million Americans are afflicted by this inflammatory arthritis today.
Conventional strategies for the prevention of gout have emphasized limiting the consumption of purine-rich foods because uric acid is a breakdown product of purine. However, it is now known that fructose also can increase uric acid, and is the only carbohydrate that can do so. The process involves the breakdown of adenosine triphosphate to adenosine monophosphate, which is a uric precursor, explained by a rheumatologist at the University of British Columbia, Vancouver.
Fructose also contributes to impaired glucose tolerance and increases insulin resistance and hyperinsultinemia, which could indirectly elevate serum uric acid levels.
Prospective studies have now demonstrated that sugary soft drinks contribute significantly to gout to say nothing of obesity, type 2 diabetes, and metabolic syndrome and in fact represent the largest single food source of calories in the American diet.
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 per week was 1.29; this rose to 1.85 for two or more servings per day, representing an 85% increase in incident gout among the highest consumers.
In another study that includes 14,761 participants aged 20 years and older from the third National Health and Nutrition Examination Survey, serum uric-acid levels increased significantly with increasing sugary soft drink consumption, with multivariate odds ratios for hyperuricemia being 1.82 among those who consumed four or more servings per day. In both of these studies, the associations were independent of risk factors for gout including alcohol use, hypertension, and body mass index.
They also found modest increases in orange juice consumption, but not for diet soda.
Data from NHANES-III, which is considered a nationally representative sample of US adults, also suggest that drinking coffee may be protective, but only if it is drunk in considerable quantities. After adjusting for age and sex, serum uric-acid levels in individuals drinking six cups of coffee per day were significantly lower by 0.43 mg/dL than in those who did not drink coffee.
The effect was not related to total caffeine intake, as modest effects were also seen with decaffeinated coffee, and it was not seen in tea drinkers. They think it derives from some other components in coffee, such as chlorogenic acid, which is a powerful antioxidant, or from noncaffeine xanthines.
In conclusion, dietary advice for 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 appear to elevate uric-acid levels, possibly because of different bioavailability, and need not be avoided.
Sugary soft drinks and other processed foods containing fructose clearly should be avoided, not only for gout prevention, but also for prevention of the common comorbidities such as hypertension and obesity. Coffee intake also is beneficial.