High adherence to a Mediterranean diet appears to be associated with a lower risk of rheumatoid arthritis (RA), especially in men and those who are seropositive, according to a study published in Arthritis Research & Therapy.

Researchers from the Karolinska Institutet performed a matched, case-controlled study that analyzed the diet of 1,721 patients with incident RA and 3,667 controls. A Mediterranean diet score (0-9) was based on a 124-item food frequency questionnaire.

Overall they found that 24% of RA patients and 28% of controls had high adherence to the Mediterranean diet (score between 6 and 9).

High adherence to a Mediterranean diet reduced the odds of developing RA by 21% (OR 0.79; 95% CI 0.65–0.96) compared to low adherence (score of 0-2).

The RA risk reduction with a Mediterranean diet only applied to men (OR 0.49; 0.33–0.73), and those who were seropositive for rheumatoid factor (RF) (OR 0.69; 95% CI 0.54–0.88) or those with antibodies to citrullinated peptides (ACPA), but not in ACPA-negative RA. Interestingly, high adherence to a Mediterranean diet did not benefit women (OR 0.94; 95% CI 0.74–1.18), and ACPA or RF-negative RA (OR 0.96; 95% CI 0.68–1.34).

These findings indicate that the Mediterranean diet score was inversely associated with risk of RA, but only in men and those who have seropositive RA. These findings may have implications in those at risk or those deemed to have "pre-clinical RA".

In other studies the Mediterranean diet has been linked with lower risk of mortality, cardiovascular diseases and cancer.