The condition afflicts around 350,000 people in the U.K., with women more likely to be affected than men.
It causes pain, swelling and inflammation in the joints and can leave people feeling generally unwell and tired.
Rheumatoid arthritis also puts sufferers at higher risk from strokes and heart attacks.
A new study published in the journal Arthritis Research and Therapy found that a gluten-free vegan diet -- which excludes animal products -- lowered levels of "bad" cholesterol, which is linked to heart disease.
The diet also raised the levels of natural antibodies to fight compounds in the body which are implicated in arthritis, according to the study.
Experts from the Rheumatology Unit at the Karolinska Institute in Stockholm, Sweden, split a group of patients with rheumatoid arthritis, with half eating a vegan and gluten-free diet and half eating a non-vegan diet.
A total of 30 patients in the vegan group and 28 in the non-vegan group completed at least three months on the diet and were included in the final analysis.
The result showed a decrease in the total level of cholesterol and in levels of "bad" cholesterol, also called LDL, among those on a vegan diet.
There was also an increase in levels of natural protective antibodies.
In contrast, the diet among the control group did not influence cholesterol values significantly.
Of the results of the vegan diet, the authors said, "There is now a large body of evidence indicating that this change of lipid profile is favorable in relation to atherosclerosis and cardiovascular disease, and this diet therefore is likely to be antiatherogenic also in rheumatoid arthritis.
"We also report that both BMI and weight decreased significantly in the vegan diet group, which was not the case in the control group."
The authors recommended a larger study to help confirm their findings.
A spokeswoman for the Arthritis Research Campaign said the study would have to be replicated in larger numbers before firm conclusions could be drawn but was still of "great interest."
"The role of diet and how it can reduce the symptoms of rheumatoid arthritis tends to be exaggerated," she said.
"However, we do know that, for example, eating oily fish can reduce inflammation, and risk factors for developing the condition include high consumption of red meat and low consumption of fruit and vegetables, so diet does play some role, however limited."
Professor David Scott, chief medical adviser to the National Rheumatoid Arthritis Society, added, "This has lots of potential value, so we should certainly encourage this group's research whilst keeping an open mind about its more widespread implications."
From the March 31, 2008, Prepared Foods e-Flash