Specific Composition Diets and Improvement of Symptoms of Immune-Mediated Inflammatory Diseases in Adulthood—Could the Comparison Between Diets Be Improved?

Diet is considered a possible cofactor, which affects the immune system and potentially causes dysregulation of intestinal homeostasis and inflammation. This study aimed to review the quality of evidence on the effects of specific diet composition on symptoms of immune-mediated inflammatory diseases (IMIDs), including rheumatoid arthritis (RA), spondyloarthritis, multiple sclerosis (MS), inflammatory bowel disease (IBD) [remission maintenance of Crohn’s disease and ulcerative colitis], psoriasis and psoriatic arthritis in adult patients. We conducted a review of meta-analyses and Cochrane systematic reviews using PubMed and EMBASE, from inception to September 2024, and Google Scholar. The methodological quality of the meta-analyses was assessed using the AMSTAR 2 rating system. Three Cochrane systematic reviews and eight meta-analyses were evaluated. Some specific composition diets have been shown to reduce the symptoms of RA, IBD, and MS and improve activity parameters in IBD and RA, with critically low or low levels of evidence. The reduction in inflammatory biomarker levels is unclear. This review summarizes the global evidence for specific dietary interventions, mostly with anti-inflammatory properties due to their components, to improve IMID symptoms, clarifying the weaknesses of clinical trials and dietary meta-analyses with critically low or low levels of evidence; and shows the need to use indices such as the Dietary Inflammatory Index, which allows diets to be classified by their pro-inflammatory or anti-inflammatory food content, to better compare diet groups in clinical trials. The difficulty of obtaining high-level evidence from dietary studies is apparent and may delay the application of the results. Clinicians should be aware of the role of diets with anti-inflammatory properties as a complement to pharmacological treatments in IMIDs.