Exploring the Relationship Between Gut Health and Autoimmune Diseases: A Systematic Review and Meta-Analysis

Autoimmune diseases (AIDs) are multifaceted, chronic illnesses characterized by immune dysregulation and systemic inflammation. Newer evidence has pointed a finger at the human gut microbiota, a trillion-fold population of microorganisms that inhabits the human GI tract, as a major influential modulator of immune reactivity and a significant contributor to autoimmune pathogenesis. This systematic review will seek to address how the literature correlates with systematic changes in the gut microbiota in AIDs as well as explore mechanistic associations with biological processes like intestinal permeability and modulation of the immune system, coupled with determining the effectiveness of microbiota-directed interventions. An extensive literature search was conducted in PubMed, Embase, Cochrane Central, and Web of Science, involving the availability of studies until May 2025. The eligible studies included observational studies, randomized controlled trials, and relevant mechanistic research regarding autoimmune diseases and alterations of the gut microbiome or administered interventions. Data extraction and risk of bias (ROB) assessments were performed by two independent reviewers, and a narrative synthesis with an illustrative meta-analysis was applied. Inclusion criteria were met by 10 studies, encompassing various autoimmune diseases, including systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), multiple sclerosis (MS), type 1 diabetes mellitus (T1DM), autoimmune thyroid diseases (AITDs), and psoriasis. Familiar patterns of microbiome dysbiosis were identified, such as a reduction in microbial diversity, increased intestinal permeability, and the expansion of pro-inflammatory species like Ruminococcus gnavus. Dietary interventions, fecal microbiota transplantation, and probiotics demonstrated positive effects on clinical outcomes and immune measures across multiple studies. The meta-analysis revealed that microbiota-directed interventions significantly improved disease activity and immune response markers in AIDs, indicating a robust link between gut microbiota composition and autoimmune pathology. In autoimmune disorders, gut microbiota is a key factor in immunopathology. Gut biology as an adjunct interventional strategy provides potential in managing these diseases. Additional studies are required to help standardize methods and identify microbial targets specific to diseases that can then be addressed through therapeutic interventions.