Role of Diet in the incidence of Gout
Approximately 1% of the U.S. population is estimated to have gout, the majority of whom are male. While dietary triggers in prevalent gout are well established, little is known about the effect of diet on incident gout. Here, Choi et al (NEJM 350:1093, 2004) examine the association of diet on the development of gout in a large, prospective cohort of non-physician health professionals.
Methods: Participants in the Health Professionals Follow-up Study with no prior history of self-reported gout were studied. This longitudinal study of male non-physician health professionals (dentists, pharmacists, veterinarians, etc) begun in 1986 included semi-quantitative food frequency questionnaires administered in 1986, 1990, and 1994. In addition, questionnaires sent every two years asked whether participants had received a new diagnosis of gout. A confirmatory questionnaire, asking specific questions related to the components of the ACR criteria for a diagnosis of gout, was sent to each of the incident gout cases in 2001. Verification of diagnostic criteria by chart review was confirmed.
For analysis, subjects were classified into quintiles based on the cumulative average of self-reported intake of each food group (meat, seafood, purine-rich vegetables, dairy products, low-fat dairy products, total protein, and animal protein) from all three food frequency questionnaires. Information on potential confounding variables, such as BMI, hypertension, diuretic use, fluid intake, alcohol use, and history of renal insufficiency, were collected.
Results: Over the twelve-year study period, 1332 self-reported cases of gout were identified. Of the1064 responders to the supplemental gout questionnaire, 730 (69%) met ACR criteria for a diagnosis of gout. Analysis was conducted on these 730 respondents. Among the incident cases of gout, the majority were in the 50-64 year age range. Among all of those surveyed, men who consumed more protein or dairy products tended to consume less daily alcohol.
The risk of gout was significantly greater in the quintile of highest total meat or seafood intake (multivariate relative risk 1.41 and 1.51 respectively) compared to the lowest quartiles of intake.
Incident gout was decreased with increasing intake of dairy products, with significant protective effects of low-fat dairy (multivariate relative risk 0.58 for the highest quintile of intake) compared with high-fat dairy (multivariate relative risk 1.00 for the highest quintile of intake).
An increased risk of gout was not associated with higher intake of purine-rich vegetables, or totals of animal or vegetable protein in the diet. In fact, men in the highest quintiles of vegetable or dairy protein intake demonstrated a significantly lower incidence of gout (multivariate relative risk 0.73 and 0.52 respectively for highest quintile of intake compared to lowest quintile). Increasing alcohol intake did not tend to influence the above associations. Likewise, the only influence of BMI on the increased risk of developing gout was observed in men with a BMI of less than 25 and with increasing intake of seafood.
Conclusions: Increased intake of meat and seafood is associated with an increased risk of incident gout. Increasing intake of low-fat dairy products as well as vegetable protein is associated with a decreased risk of incident gout. Increasing intake of purine-rich vegetables or animal protein is not associated with a significant increase in risk of developing gout.
Editorial Comments: This investigation confirms some assumptions about diet and gout, while dispelling others. The long-held tenet that heavy meat and seafood intake in the diet is associated with gout is confirmed here. Surprisingly, however, was the lack of an association between increasing intake of animal protein or alcohol. This study also confirmed the previously unproven suggestion that higher intake of dairy products lessens the risk for developing gout. It is important to remember when trying to apply these results to clinical practice that this study examines the influence of diet on incident gout. Whether the intake of these foods causes gout in otherwise gout-free men or whether increasing intake of these foods simply promotes hyperuricemia past a threshold in gout-prone men cannot be answered by this type of study. Lastly, although this study targeted middle-aged men (the most common group affected by gout), this particular group, health-care professionals, represent a relatively restricted population. Therefore, the results of this study may not be generalizable (e.g. to women, men in lower socio-economic brackets, etc)