High adherence to a Mediterranean diet may reduce the risk of developing rheumatoid arthritis (RA), according to study results published in Arthritis Research & Therapy. However, this association was only statistically significant in men and in seropositive RA.

This study included data from the Swedish Epidemiological Investigation of Rheumatoid Arthritis (EIRA), which was a population-based case-control study. Data on 1721 participants with incident RA and 3667 controls matched for age, gender, and residential area were included. The researchers calculated participants’ Mediterranean diet score on a scale of 0 to 9 based on a 124-item food frequency questionnaire.

In total, 24.1% of participants with RA had high adherence to the Mediterranean diet defined as a score of 6 to 9 compared with 28.2% of controls.

After adjusting for BMI, educational level, physical activity, the use of dietary supplements, energy intake, and smoking status, the researchers found that high adherence to the Mediterranean diet reduced the risk of developing RA by 21% (odds ration[OR], 0.79; 95% CI, 0.65-0.96) compared with low adherence (score from 0 to 2).

When they stratified the results by gender, the researchers found that the effect became more pronounced in men (OR, 0.49; 95% CI, 0.33-0.73) and was not statistically significant in women (OR, 0.94; 95% CI, 0.741.18).

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In participants who were rheumatoid factor (RF)-positive, the results indicated an association between high adherence score and low risk for RA (OR, 0.69; 95% CI, 0.54-0.88). However, this association was not seen in participants who were RF-negative (OR, 0.96; 95% CI, 0.68-1.34).

“These results add to the accumulating evidence showing the importance of diet in the primary prevention of RA,” the researchers wrote. “However, we need to acknowledge that the mechanisms and impact of potential dietary guidelines might [have to] differ between RA sub-groups.”

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Reference

Johansson K, Askling J, Alfredsson L, et al. Mediterranean diet and risk of rheumatoid arthritis: a population-based case-control study [published online August 9, 2018]. Arthritis Res Ther. doi:10.1186/s13075-018-1680-2