Study clarifies impact of diet on the risk of gout

03/05/04

Meat and seafood associated with greater risk, dairy products may be protective

A new study has clarified the role of diet in the risk of developing gout – the most common form of inflammatory arthritis in men. By taking a comprehensive look at a broad range of dietary factors, the report confirms the suspicion that consumption of purine-rich meats and seafood increases the risk of gout. It also determines that purine-rich vegetables and overall protein intake do not raise risk. Appearing in the March 11 New England Journal of Medicine, the study also finds that intake of dairy products, particularly low-fat, may be protective against gout.

"The association of purine-rich foods with gout had long been suspected but never proven," says Hyon Choi, MD, DrPH, 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." The report is part of the Health Professionals Follow-up Study, which is based at the Harvard School of Public Health (HSPH).

A painful condition affecting more than 5 million adults in the U.S., gout is caused by deposits of uric acid in connective tissue, often in joints of the feet or ankles, that lead to inflammatory arthritis. Symptoms include swelling, redness, stiffness, and severe pain. Although attacks of gout can subside in a few days, 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.

Initiated in 1986, the Health Professionals Follow-up Study has gathered information regarding the relationship between dietary factors and several illnesses from more than 50,000 men employed in the health professions. Every two years participants complete questionnaires regarding their diseases and health-related topics like smoking and exercise, and every four years the questionnaires also collect comprehensive dietary information.

The current investigation began with 47,000 men who did not report a history of gout at the study's outset. Participants who subsequently reported developing gout were surveyed to verify that they met standard criteria for the disorder, confirming a diagnosis of gout in 730 men by 1998. The researchers then analyzed dietary information that all study participants provided in 1986, 1990 and 1994 to determine how diet related to their risk for gout.

The study results confirmed that consumption of meat – particularly beef, pork and lamb – significantly increases the risk of gout and that consumption of 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 explains. Choi is an instructor in Medicine at Harvard Medical School.

While this study examined only men, in whom gout is more common, the investigators strongly 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 say.

Choi's co-authors include senior author Gary Curhan, MD, ScD, of HSPH and the Channing Laboratory at Brigham and Women's Hospital (BWH), Karen Atkinson, MD, MPH, of the MGH Rheumatology Unit; and Elizabeth Karlson, MD, and Walter Willett, MD, DrPH, of BWH and HSPH. The study was supported by grants from the National Institutes of Health and TAP Pharmaceuticals.

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