A study offers proof that diet modification can have a dramatic effect on the risk of recurrent gout attacks. Published online in Annals of the Rheumatic Diseases, the study found that for people with gout, eating a lot of purine-rich foods – like red meat, organ meat, certain fish and vegetables – over a short period of time can increase the risk of a gout attack almost fivefold compared to their risk when eating fewer purine-rich foods.

Avoiding or limiting purine-rich foods is not new advice for gout patients. When purines are metabolized by the body, they break down into uric acid. Gout occurs when excess uric acid in the bloodstream – called hyperuricemia – builds up too quickly or can’t be eliminated fast enough and is, instead, deposited as needle-shaped crystals in the tissues of the body, including joints, causing intense pain. In theory, avoiding or reducing purine-rich food should reduce the risk for a gout attack.

This scientific study, conducted by researchers at the Boston University School of Medicine, is the first to formally test the hypothesis, show a direct association between purine intake and gout attacks, and quantify the risk. The authors conclude that ingestion of purine-rich foods can actually trigger a gout attack within days – and that the risk rises as more purines are included in the diet.

“The biological mechanisms linking purine-rich food intake with hyperuricemia as well as with [the] incidence of gout are well understood,” says study co-author Yuqing Zhang, professor of medicine and public health at Boston University. “Our study added new evidence that [an] increase of purine intake within a short period could trigger gout attacks among subjects with pre-existing gout.”

Purines, which are found in protein-rich foods, are most abundant in food from animal sources – especially organ meats and some oily fishes, such as anchovies and sardines. But some vegetables contain purine, too, including spinach, mushrooms, beans, peas, asparagus and cauliflower.

The study involved more than 630 participants with a history of gout within the previous 12 months. Participants were asked to fill out a lifestyle questionnaire over the Internet every three months – data that served as a control – then an additional questionnaire any time a gout attack occurred.
 

During the one-year surveillance period, approximately two-thirds of the participants experienced at least one new gout attack, resulting in 1,247 flare episodes. Those experiencing a flare were questioned about their diet in the two days leading up to the attack. Actual analysis was restricted to cases in which gout symptoms were unmistakable – with redness over the joint, maximal pain at 24 hours and treatment with at least one anti-gout medication, such as colchicine, a nonsteroidal anti-inflammatory drug, also known as an NSAID, or a corticosteroid.

The study broke down the reported gout episodes into five groups, based on amount of purine ingestion in the 48 hours before the attack – a timeframe the authors refer to as the “hazard period.” The results show a clear escalation in acute gout attacks as purine ingestion increased.

“Our study showed that risk of recurrent gout attacks increased almost 40 percent if intake of purine went from less than 1 gram to 1.75 grams over two days,” Zhang says. The fivefold increase in gout-flare risk came at purine ingestion levels about twice that level – and the risk persisted even in those taking the uric acid-lowering agent allopurinol.

Registered dietitian Sandra Allonen, at Beth Israel Deaconness Medical Center in Boston, says practitioners have known intuitively about the connection between a purine-rich diet and gout, but that this new study provides a solid rationale for recommending gout patients limit purine intake.

The study looked not only at total purine intake preceding a gout attack – but where that purine was coming from. And the results point to animal sources of purine being more of a problem than vegetable sources – in part, the authors say, because vegetables contain less purine than meats. The authors also note that in a previous study, ingestion of vegetable protein actually lowered the risk of gout.

The study brings up important nutrition questions for those with gout: What and how much should you eat to keep gout attacks to a minimum, and what are the “safest” sources of protein (since they can contain high amounts of purines).

Allonen, who provides nutritional counseling to gout patients, says the average person needs a lot less protein than they probably are taking in. She uses a formula based on weight to determine daily protein needs. A 150-pound, generally healthy person, for example, needs about 54 grams, or 7 to 8 ounces, of protein daily, she says – even if they are prone to gout attacks.

For people with gout, “I recommend the more alkaline proteins found in plant-based foods [first], then fish, then poultry and then red meat,” she says.

As for general dietary recommendations in those with gout, Allonen says it’s case-by-case. If they have regular gout attacks, “I would be more inclined to advise them to be careful with purine-rich foods. If their gout attacks are [few and far] between, I'd be a bit more liberal with their diet and work closely with the health-care provider who is overseeing their gout issues.”