Efficacy of diets with specific compositions to reduce the symptoms of immune-mediated diseases. Narrative review

Diet is considered a possible cofactor that participates in the inflammatory cascade and influences at the molecular level, microbiota, and intestinal permeability, affecting the immune system, and potentially causing dysregulation of intestinal homeostasis, inflammation, food intolerance, or food allergy. This study aimed to review the evidence on the effects of specific diet composition on the symptoms of some immune-mediated diseases -rheumatic diseases, multiple sclerosis, inflammatory bowel disease, and psoriasis-. We conducted a narrative review of meta-analyses, and Cochrane systematic reviews, on PubMed, EMBASE, and Google Scholar, from inception to July 2023. The methodological quality of meta-analyses was assessed using AMSTAR 2 rating. Eight meta-analyses showing the level of evidence for specific diets in IMD symptoms were selected and evaluated. A tendency to the reduction in pain, fatigue, and quality of life in the studied IMDs, and to improve inflammatory markers in rheumatoid arthritis with diets reducing inflammatory foods, and no differences were observed for other outcome measures, with a very low level of evidence. This review provides clarity on the weaknesses of clinical trials and meta-analyses on diet, updates the global evidence on diet to improve immune-mediated disease symptoms, and analyzes the influence of dietary mechanisms. Likewise, it shows the beneficial effects of diets reducing inflammatory foods in decreasing the symptoms of immune-mediated diseases, however, the included studies had a very low level of evidence. The difficulty in obtaining high-level evidence is clear in diet studies, and this can delay the application of the results.