The Mediterranean Diet (MD) is one of the healthiest dietary pattern existing and consists in the high consumption of products like fruits, vegetables, legumes, unrefined cereals and nuts, the moderate consumption of fish, poultry and dairy products as cheese and yoghurt, and the low consumption of red meat products. Olive oil is used as the main edible-fat source and wine is consumed in a regular, but moderate, basis with a meal. The reduction in overall mortality and morbidity has been linked to a greater adherence to the MD and this food pattern is highly proposed as a beneficial dietary approach for patients with inflammatory diseases.

Studies have shown rheumatoid arthritis disease characteristics namely, inflammatory activity disease, physical function and vitality, may be clinically related to MD pattern, particularly when compared to a western diet. One study, after 12 weeks of intervention, patients in the MD group showed a significant improvement in Disease Activity Score (28 joints), Health Assessment Questionnaire, whereas subjects in the control group displayed no significant changes in these parameters. In another study, after 6 months, patient global pain (Visual Analog Scale), and morning stiffness were significantly improved in the intervention group when compared to controls.

Rich fibre foods such as fruit, vegetables, and legumes, all regularly consumed by individuals who practice a MD pattern, have the ability to become degraded by the gut bacteria ‘Firmicutes’ and ‘Bacteroidetes’ bacteria, leading to high feacal Short Chain Fatty Acids (SCFA’s). Fibre is the most well-known nutrient with an important impact on microbiota. Diets rich in this nutrient increase SCFA producing bacteria, with benefits on intestinal barrier structure. Particularly the butyrate strengthens the barrier and decreases intestinal permeability and bacterial translocation. This has been shown to prevent the activation of undesirable local and systemic inflammatory responses. The changes in gut microbial ecology and associated SCFA driven immune modulation can, in a logical way, explain the mechanisms behind clinical amelioration of RA in individuals exposed to MD.