Arthritis

Results of a study of people living in southern Greece suggest that eating hearty amounts of olive oil and cooked vegetables may reduce the risk of developing rheumatoid arthritis, researchers report.

Rheumatoid arthritis is a chronic inflammatory disease of the joints. Its cause is unknown, but genes, infectious agents, hormones, and diet have been suggested as possible causes.

Some reports have suggested that fish oil and vegetable oil in the diet may help relieve arthritis symptoms, but research has not confirmed that these foods have a protective effect. The new study findings suggest that olive oil and cooked vegetables may, in fact, reduce arthritis risk.

"Consumption of both cooked vegetables and olive oil was inversely... associated with risk of rheumatoid arthritis," according to the team of Greek and U.S. researchers, meaning that individuals who had higher levels of these oils in their diets had a lower risk of developing rheumatoid arthritis.

The team did not find evidence that fish consumption reduced the risk.

The study was based on data from 145 patients with rheumatoid arthritis and 188 people who did not have the disease. All of the study participants lived in southern Greece and provided demographic, socioeconomic, family and medical information.

The consumption of more than 100 food items was determined through interviews. The research team, led by Athena Linos of the University of Athens Medical School in Greece, estimated the number of days per year that subjects consumed olive oil and tallied these numbers to estimate consumption over a lifetime. They then calculated the likelihood of developing rheumatoid arthritis in relation to consumption of olive oil, fish, vegetables, and other food groups.

The investigators found that people who consumed the least olive oil were 2.5 times more likely to develop rheumatoid arthritis than those who consumed the most olive oil.

Further, those who consumed the most cooked vegetables had a 75% lower risk of developing rheumatoid arthritis, they note.

Although the mechanism by which these foods might lower the risk remains unclear, the authors suggest that antioxidant substances could play a role. Olive oil is rich in vitamin E, which has "a beneficial biological role as (a free) radical quencher." Free radicals are molecules involved in several chronic diseases as well as aging.

"It is possible that heat destroys the cell walls of cooked vegetables, helping the body to absorb more of a potentially beneficial substance," the team writes in the December issue of the American Journal of Clinical Nutrition. But they add that the "specific beneficial substances in cooked vegetables remain to be identified."

Linos and colleagues also note that the typical American diet is rich certain types of fat that are broken down to hormones that promote inflammation. The fatty acid in olive oil, on the other hand, is broken down to hormones that inhibit inflammation.


SOURCE: American Journal of Clinical Nutrition 1999;70:1077-1082.