Effect of Probiotic and Synbiotic Oral Supplementation in Autoimmune Diseases: An Updated Systematic Review and Meta-Analysis of Randomized Controlled Trials

Background: Autoimmune diseases affect 5–10% of the global population. Probiotic supplementation has emerged as a potential adjunctive therapy in managing inflammation associated with these conditions. This systematic review and meta-analysis aimed to examine the effectiveness of oral probiotics in patients with autoimmune diseases for managing inflammation. Methods: A literature search of PubMed, EMBASE, and Cochrane CENTRAL was performed up to 18 June 2024. Eligible studies were randomized controlled trials (RCTs) examining the effects of oral supplementation of probiotics, synbiotics, or prebiotics in patients with established autoimmune diseases. The primary outcome was changes in inflammatory markers, including interleukin (IL)-6, IL-10, IL-1β, tumor necrosis factor (TNF)α, and high-sensitivity C-reactive protein (hs-CRP). Results: Twelve RCTs involving 703 patients were included. Significant reductions were observed in levels of IL-6 (pooled standardized mean difference [pSMD] = −0.83; 95% confidence interval [CI]: −1.30, −0.37), IL-10 (pSMD = −0.30; 95% CI: −0.61, −0.00), TNFα (pSMD = −0.41; 95% CI: −0.77, −0.06), and hs-CRP (pSMD = −0.71; 95% CI: −1.18, −0.23) in patients taking probiotic supplementation. Subgroup analysis revealed that in rheumatoid arthritis (RA) patients, the probiotics group showed greater improvements in IL-6, IL-1β, and TNFα compared to the controls. In multiple sclerosis (MS) patients, the probiotics group demonstrated greater improvements in hs-CRP. Conclusions: Oral probiotic supplementation lowers the levels of some inflammatory markers in patients with autoimmune diseases. Further studies with longer follow-up durations are needed to confirm these findings and explore the long-term benefits of probiotics in this population.