The new study is based on food diaries kept by about 260 people, a third of whom had inflammatory arthritis, such as rheumatoid arthritis, in at least two joints. Participants kept detailed food journals for seven days, weighing their food for accurate records.
Dorothy Pattison, PhD, and colleagues reviewed the diaries to see if any foods were associated with inflammatory arthritis.
Among the diary entries, red meat stood out.
Participants who ate the most red meat were more than twice as likely to have inflammatory arthritis. Forty-two percent of inflammatory arthritis patients reported eating more than 58 grams of red meat per day. Those frequently combining red meat and other meats also had a higher risk of inflammatory arthritis.
But red meat wasn't alone. Protein in general was linked to inflammatory arthritis. Participants eating the most protein from all sources (more than 75 grams daily) almost tripled their risk of inflammatory arthritis compared with those with the lowest protein intake (less than 62 grams).
That doesn't make red meat the dietary bad guy. The researchers don't blame it for inflammatory arthritis. They're not sure exactly what's at work.
Possibilities could include collagen, which occurs naturally in meat, or additives or even infectious agents, say the researchers. At this point, it's guesswork. "There is no evidence as to what might be important in relation to rheumatoid arthritis," Pattison and colleagues write in Arthritis & Rheumatism's December issue.
Identifying causes of rheumatoid arthritis has challenged researchers for years. It's believed that lifestyle factors may account for about 40 percent of the risk of developing rheumatoid arthritis.
For instance, smoking has consistently been flagged as a risk factor. In Pattison's study, inflammatory arthritis patients were much more likely to be smokers. However, the findings about red meat weren't affected by taking smoking into consideration.
Pinning down rheumatoid arthritis' dietary influences has been tougher. Everything from coffee (which may increase risk) to fish oil (which may be protective) has been explored. In some cases, such as with alcohol, results have been inconsistent.
And that's just the beginning. Studies have gotten down to the nitty-gritty details of how fruits and vegetables are prepared and what compounds and vitamins they contain.
A few years ago, researchers found that people who rarely eat fruit and had low levels of vitamin C intake were up to three times more likely to develop inflammatory arthritis. This time, the link was a little weaker but still present.
Scientists aren't able to prescribe a menu that eliminates rheumatoid arthritis risk. But maintaining a healthy diet can't hurt.
Sources: Pattison, D. Arthritis & Rheumatism, December 2004; vol 50: pp 3804-3812. WebMD Medical Reference provided in collaboration with The Cleveland Clinic: "Understanding Arthritis: What Is Inflammation?" News release, Arthritis & Rheumatism.
By Miranda Hitti
Reviewed by Michael W. Smith, MD
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