The research, published in today's issue of the New England Journal of Medicine (vol 350:1093-1103), confirms the suspicion that consumption of meats and seafood increase the risk, although overall protein intake does not play a role in this risk. The study also found that intake of dairy products, particularly low-fat dairy, may be protective against the disease.
"The association of purine-rich foods with gout had long been suspected but never proven," said Hyon Choi of the Massachusetts General Hospital (MGH) Rheumatology Unit, the paper's lead author. "Any contribution of protein intake to risk was uncertain, and this is the first evidence that dairy products can be strongly protective." Gout is caused by deposits of uric acid in connective tissue, often in joints of the feet or ankles that lead to inflammatory arthritis. Repeated attacks can cause permanent joint damage, and the disease often results in substantial disability, occupational limitations and frequent medical care.
Treatment includes the pain-relieving drugs called NSAIDs (non-steroidal anti-inflammatories) and for more serious outbreaks, corticosteroid drugs like prednisone. Most patients with gout eventually require long-term treatment with medications that lower blood uric acid levels.
Because uric acid is formed by the breakdown of purines - compounds found in all human tissues and in many foods - gout patients have long been advised to avoid purine-rich foods. And since many animal products are rich in purines, avoidance of animal proteins has also been recommended. But the association of these foods with the risk of gout was never confirmed by prospective studies.
The new findings are based on a 12-year study, using the Health Professionals Follow-up Study in the US to determine how diet related to risk of gout. Consumption of meat - particularly beef, pork and lamb - significantly increased the risk of gout and all types of seafood tended to carry an even higher risk.
Notably, no increased risk was seen with consumption of purine-rich vegetables - which include peas, beans, mushrooms, cauliflower and spinach - or with overall protein intake. The study actually found a potential protective effect from vegetable and dairy proteins.
The protective impact of dairy products had been suggested by an earlier study finding that a dairy-free diet could increase uric acid in the blood, and the current report confirmed that increased consumption of low-fat dairy products significantly reduced the risk of gout.
Choi notes that this study's results are probably most relevant to individuals who have a history of gout or are at increased risk because of family history or other factors.
"Dietary manipulation and behavioral modification to reduce risk of gout may have a much more substantial impact than currently believed. Reducing red meat consumption may be recommended because it also has been associated with such problems as colon cancer and diabetes. At the same time, healthy foods such as vegetables do not need to be restricted."
"Recommendations for seafood or dairy intake should be individualized with a physician or dietitian, taking into account their potential impact on any other health issues," he added.
While this study examined only men, in whom gout is more common, the investigators suspect that the results would also apply to women. Future studies to investigate whether reducing meat and seafood consumption or increasing low-fat dairy intake actually prevents outbreaks in gout patients could be valuable, the researchers added.