Summary

Objective: Rheumatoid arthritis (RA) is one of the most prevalent autoimmune diseases worldwide. Dietary interventions can be of great value in treatment of RA, since current drug therapies cause many side-effects and work insufficiently in a substantial number of patients. Therefore we aimed to assess the effects of dietary interventions on inflammatory markers and the gut microbiome in patients with autoimmune diseases and to extrapolate the results to rheumatoid arthritis. Methods: This systematic subreview was part of a larger systematic review. We included randomised controlled trials and clinical intervention studies in patients with autoimmune diseases, investigating the effect of dietary interventions on inflammation measured via CRP and the gut microbiome diversity, composition and metabolites. Results: 10 studies were included. We distinguished three main dietary groups: high-fiber and Mediterranean diets, specific carbohydrate and low FODMAP diets and fiber supplements and synbiotics. High-fiber and Mediterranean diets moderately lowered CRP while the specific carbohydrate diets were most effective at reducing CRP. The low FODMAP diet and fiber supplements did not lower CRP. No overall patterns of change were observed in gut microbiome composition, diversity and metabolites were observed due to these diets. Conclusion: Diets excluding added sugars, processed foods and unfermented dairy products were able to reduce CRP in patients with autoimmune diseases. No noticeable changes were observed in gut microbiome composition after these dietary interventions.