Mediterranean diet and rheumatic diseases

Dietary habits have long been known to have a critical role on human health and diseases. Recently, growing evidence has emerged on the impact of dietary factors in shaping the pathogenesis and progression of several chronic conditions, including rheumatic diseases. Food-derived molecules have been shown to act as epigenetic modifiers, affecting immune response and the so-called mosaic of autoimmunity through differential interactions with the gastrointestinal epithelial barrier, the mucosal immune system and intestinal microbial flora.1 It is therefore not surprising that nutritional intervention has now been part of a broader multidisciplinary approach to several chronic diseases, becoming of central concern for both patients and clinicians. Regarding rheumatic diseases, this approach is supported by the evidence of a dietary-based inflammatory phenotype, which has derived from a progressive westernization of diet. In fact, modern western diets, characterized by high consumption of refined carbohydrates, added sugars and salty foods, could progressively induce a pro-inflammatory state and therefore autoimmune diseases.2,3 It has in fact been shown that visceral adiposity drives naïve myeloid cells into M1 pro-inflammatory macrophages and that high concentration of sodium chloride induces differentiation of Th17 cells and overproduction of inflammatory cytokines.2 The aim of nutritional intervention in the course of rheumatic diseases is instead to provide a dietary regimen centered on a high anti-inflammatory and antioxidant profile of nutrients.2 To this purpose, different dietary approaches have been investigated, mainly focusing on rheumatoid arthritis (RA), as the prototypical chronic inflammatory disease.4 Among the proposed dietary approaches, the Mediterranean diet (MedDiet) is the best-balanced and most complete diet and the only one to support substantial health benefits for rheumatic diseases.2 Originating in the rural areas of the upper Mediterranean basin, MedDiet is characterized by a large variety of nutrients reflecting the eating habits and geographical resources of those territories. It consists in an abundant intake of antioxidant and anti-inflammatory compounds derived from extra-virgin olive oil (EVOO), vegetables, fresh fruits, nuts, whole grains, fish and from a small number of dairy products and from red wine and an appropriate lipid profile with low intake of saturated fats and optimal ratio of n-6 to n3 polyunsaturated fatty acids (PUFAs).2 There is accumulating evidence that MedDiet, beyond its preventive role on general health, could also be beneficial for most rheumatic diseases, offering effective integrative treatments to a pharmacological approach.2 A recent systematic review has confirmed the beneficial effect of MedDiet in reducing pain and increasing physical function in RA patients.5 More specifically, a large number of experimental and observational studies have focused on the properties of each bioactive compounds provided by MedDiet, reporting their positive effects on rheumatic diseases progression.6 Dietary antioxidants, highly contained in red fruits, vegetables, nuts and cocoa, are a heterogeneous group of bioactive compounds with a strong anti-inflammatory function and analgesic effect.6 Interestingly, these nutrients have been recently reported to reduce pain and inflammation in experimental models and in human clinical studies of arthritis. Specifically, resveratrol, which is found in high concentrations in grapes and red wine, has been reported to potently inhibit nuclear factor kB (NF-kB) activity, preventing inflammation in RA in vitro models.6 Anti-inflammatory properties are mostly attributed to spices, traditionally an integral part of MedDiet. These contain components such as curcumin and capsaicin, which exert a regulatory effect on oxidative stress and inflammation.1,2 Curcumin has been used in Ayurvedic medicine for centuries for its properties in treating various inflammatory conditions, including psoriasis and arthritis.1 More recently, in vitro studies have reported its efficacy in suppressing inflammatory cascade by blocking NF-kB and cyclooxygenase 2 pathways and, specifically, in Correspondence: Maurizio Cutolo, Research Laboratories and Academic Division of Rheumatology, Postgraduate School of Rheumatology, Department of Internal Medicine University of Genova, Ospedale Policlinico San Martino, Viale Benedetto XV 6, 16132 Genova, Italy. E-mail: mcutolo@unige.it