Effect of Plant-Based Diets on Rheumatoid Arthritis: A Systematic Review

CONTEXT: Rheumatoid arthritis (RA) is an autoimmune disease that leads to chronic inflammation and joint damage. Various plant-based diets are thought to have effects on RA symptoms and disease activity. OBJECTIVE: Relevant literature on the effect of different types of plant-based diets on RA was reviewed. DATA SOURCES: A systematic search was conducted using the Web of Science, PubMed, Scopus, and Cochrane databases and following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. DATA EXTRACTION: Articles on observational and interventional human studies carried out in the adult population and published in English between February 2013 and April 2023 were eligible for inclusion. Articles reporting on studies performed in populations under 18 years of age, with unclear methods and results, or for which the full text was unavailable were excluded. The risk of bias in the selected studies was assessed using the Joanna Briggs Institute checklists. DATA ANALYSIS: Of 547 screened articles, 15 were included, comprising 4 cross-sectional, 2 cohort, and 9 randomized controlled trials. These studies examined the effects of various diets, including the Mediterranean, low-fat high-carbohydrate, anti-inflammatory, and vegan, on RA. Results indicate adherence to plant-based diets generally reduced disease severity and improved dietary intake, physical activity, body weight, and key clinical markers such as the Disease Activity Score-28, Visual Analog Scale score, Health Assessment Questionnaire Disability Index, erythrocyte sedimentation rate, and C-reactive protein level in patients with in RA. CONCLUSIONS: Most of the studies suggested the Mediterranean diet may positively affect the severity of RA. However, the included studies show heterogeneity. Therefore, more randomized controlled studies are needed in this area to increase understanding of the effect of diet on RA and facilitate the implementation of strategies to prevent RA. SYSTEMATIC REVIEW REGISTRATION: PROSPERO registration no. CRD42023420577.