Can soy intake affect serum uric acid level? Pooled analysis from two 6-month randomized controlled trials among Chinese postmenopausal women with prediabetes or prehypertension

Various purine-rich foods and high protein intake have long been thought to be risk factors for gout. Similarly, the possibility that the consumption of dairy products has a role in protecting against gout has been raised by metabolic studies. We prospectively investigated the association of these dietary factors with new cases of gout. Over a 12-year period, we prospectively examined the relationship between purported dietary risk factors and new cases of gout among 47,150 men who had no history of gout at base line. We used a supplementary questionnaire to ascertain whether participants met the American College of Rheumatology survey criteria for gout. Diet was assessed every four years by means of a food-frequency questionnaire. During the 12 years of the study, we documented 730 confirmed new cases of gout. The multivariate relative risk of gout among men in the highest quintile of meat intake, as compared with those in the lowest quintile, was 1.41 (95 percent confidence interval, 1.07 to 1.86; P for trend = 0.02), and the corresponding relative risk associated with seafood intake was 1.51 (95 percent confidence interval, 1.17 to 1.95; P for trend = 0.02). In contrast, the incidence of gout decreased with increasing intake of dairy products; the multivariate relative risk among men in the highest quintile, as compared with those in the lowest quintile, was 0.56 (95 percent confidence interval, 0.42 to 0.74; P for trend <0.001). The level of consumption of purine-rich vegetables and the total protein intake were not associated with an increased risk of gout. Higher levels of meat and seafood consumption are associated with an increased risk of gout, whereas a higher level of consumption of dairy products is associated with a decreased risk. Moderate intake of purine-rich vegetables or protein is not associated with an increased risk of gout. Copyright 2004 Massachusetts Medical Society

Post-hoc analyses of the GREACE and the LIFE trials have renewed the interest in elevated serum uric acid (SUA) as a factor contributing to atherosclerotic cardiovascular disease (CVD) and in the possible benefit derived from its pharmacological reduction. The results of these trials are consistent with reports indicating favourable effects of SUA lowering treatment with allopurinol on the rate of cardiovascular complications in patients with coronary heart disease, congestive heart failure and dilated cardiomyopathy. Two recent overviews have concluded that, while in population samples at relatively low risk of CVD, SUA is at best a very weak predictor of CVD, by contrast it is a significant independent predictor among subjects at high or very high risk. This raises the question of a different meaning of excess SUA levels under different circumstances. Whereas in uncomplicated obese, insulin-resistant and hypertensive patients SUA levels increase mainly as a consequence of impaired renal excretion, in conditions of local ischemia an increased production of uric acid occurs in parallel with that of reactive oxygen species (ROS). Thus, although clinical and experimental evidence suggest that uric acid has actually antioxidant properties, it is conceivable that under these conditions its antioxidant activity is overcome by the pro-oxidant and pro-inflammatory effects of ROS accumulation. At present, there is no solid evidence to recommend treatment of the mild asymptomatic hyperuricemia associated with obesity, diabetes and/or hypertension (up to 10mg/dL). By contrast, similar SUA elevations in patients at higher cardiovascular risk should be taken more seriously. A controlled trial to investigate the effects of SUA reduction in these patients, while monitoring concomitant changes in parameters of oxidative stress and inflammation, is warranted.