Psoriasis is a chronic inflammatory disease that is affected by multiple lifestyle-associated factors. In recent years, several studies have demonstrated the ability of certain foods and dietary patterns to modulate different markers related to systemic inflammation,1 which is an important component of moderate-to-severe psoriasis and is closely linked to associated comorbidities. In a meta-analysis of clinical trials, weight loss through diet was associated with a significant decrease in disease severity.2 Although these improvements could be attributed to a reduction in obesity-associated systemic inflammation, the results of the included studies showed great heterogeneity, suggesting a role of factors other than weight loss in the observed benefit. Diet composition, as mentioned above, could be one such factor.1,2 The Mediterranean diet (MD) is a great source of antioxidant and anti-inflammatory molecules, and has been associated with a decreased risk of cardiovascular and chronic inflammatory diseases.1 Accordingly, several research groups have investigated the potential benefits of MD in patients with psoriasis.

In a cross-sectional study published in 2015 by Barrea et al.,3 poor MD adherence was observed in a significantly higher percentage of psoriasis patients than controls (30.6 and 4.8%, respectively; P<0.001). Diet adherence was negatively correlated with disease severity as measured by the psoriasis area severity index (PASI). In the multiple regression analysis, consumption of olive oil was one of the main predictors of PASI score, with a correlation coefficient (r2) of 0.548 (P<0.001). The largest study in this field is a cross-sectional study published in 2018 in JAMA Dermatology4 that included 35735 subjects from the NutriNet-Santé cohort. Of the participating subjects, 3557 had psoriasis, which was classified as severe in 878 patients. In the multivariate analysis, after adjusting for variables such as age, sex, weight, and cardiovascular risk factors, the percentage of patients with severe forms of the disease was significantly lower among the groups with the greatest adherence to the diet. Castaldo et al.5 evaluated the effect of a very low-calorie ketogenic diet for 4 weeks followed by hypocaloric MD for 6 weeks in a group of overweight/obese patients with psoriasis without systemic treatment. The authors observed significant reductions in weight and improvements in PASI and quality of life. Interestingly, they observed no linear correlation between weight loss and PASI, suggesting that the anti-inflammatory effect of ketone bodies and other dietary components contributed to the observed benefits. Finally, a recent study reported an inverse and weight-independent correlation between psoriatic arthritis activity and MD adherence, suggesting a potential benefit of this dietary pattern in these patients.6Table 1 summarizes published studies evaluating the effect of MD in psoriasis and/or psoriatic arthritis.

In conclusion, the available evidence indicates that MD may be associated with less severe forms of psoriasis and/or psoriatic arthritis. Bearing in mind that reduced severity was independent of body mass index in several studies,4–7 it is possible that the beneficial effects of this dietary pattern are due to more than mere weight loss. However, more experimental longitudinal studies will be necessary to consolidate these findings and to precisely define the role of MD in the treatment of this disease.