A new review finds no definitive connection between diet and rheumatoid arthritis (RA), a disease in which the body’s immune system attacks the lining of the joints.

As an individual’s rheumatoid arthritis progresses, his or her joints can become swollen and stiff, reducing mobility. While treatments are available to relieve some of these symptoms, no cure exists.

Although sufferers of rheumatoid arthritis have turned to a variety of special diets, the new review of 15 studies found little evidence that changing their diets made any significant difference.

“There are different theories behind certain diets,” said Kare Hagen, the lead review author. “There are some reports showing that food allergy or intolerance is present or even common in RA patents.” However, she said, “No body of evidence exists for dietary intervention for RA.”

Hagen is a senior researcher at the National Resource Center for Rehabilitation in Rheumatology of the Diakonhjemmet Hospital in Oslo, Norway.

The new review appears in the latest issue of The Cochrane Library, a publication of The Cochrane Collaboration, an international organization that evaluates medical research. Systematic reviews like this one draw evidence-based conclusions about medical practice after considering both the content and quality of existing medical trials on a topic.

Of the review studies, one found that fasting followed by 13 months on a vegetarian diet might reduce pain by 1.89 percent on a scale of zero to 10, but had no effect on physical function or morning stiffness.

In another study, a 12-week Mediterranean diet reduced pain by 14 percent, but had no effect on physical function or morning stiffness. The Mediterranean diet is high in fruit, vegetables, cereals and legumes, fish and olive oil, and low in red meat.

Two studies looked at the use of an elemental diet, consisting of hypoallergenic, easy-to-digest food. The diet, sometimes prescribed for patients with Crohn’s disease, made no significant differences in pain, function or stiffness in participants with rheumatoid arthritis. Studies on vegan diets and elimination diets, which remove one or more food items from the diet to see if improvement occurs, were inconclusive.

Overall, study participants who were placed on a diet were twice as likely to drop out as those in control groups were. Those who did change their diet lost more weight, up to six and a half pounds, without intending to do so — not necessarily a good thing for these people.

Reviewers explained that some of the diets, without special planning, could cause a deficiency in important vitamins and minerals. People with rheumatoid arthritis might already find it difficult to buy and prepare food, so a special diet could put them at a further disadvantage.

“Considering that many RA patients are already at nutritional risk, we cannot consider weight loss as a solely beneficial effect,” Hagen said.

“As the authors conclude, there is not enough information to make a strong, scientifically based recommendation regarding use of dietary changes to control RA inflammation symptoms,” said Mark Wenner, M.D., a professor at the University of Washington School of Medicine. “One of the problems is that there are few well-done clinical studies that have investigated the influence of diet on RA inflammation and the studies that have been done differ from one another.”

Still, diet does offer other benefits for related conditions for which RA patients are at increased risk, Wenner said. “For example, attention to dietary and nutritional factors that lower risk for cardiovascular disease and osteoporosis is particularly valuable for RA patients.”

For Wenner, the review confirmed the benefits of the Mediterranean diet, which he recommends as a healthy heart diet. While the improvement in rheumatoid arthritis generally is modest, he said, the Mediterranean diet poses little risk.

The Cochrane Collaboration is an international nonprofit, independent organization that produces and disseminates systematic reviews of health care interventions and promotes the search for evidence in the form of clinical trials and other studies of interventions.

Hagen KB, et al. Dietary interventions for rheumatoid arthritis. The Cochrane Database of Systematic Reviews 2009, Issue 1.

Source: Health Behavior News Service