The therapeutic effect of probiotics on rheumatoid arthritis: a systematic review and meta-analysis of randomized control trials

Rheumatoid arthritis is an autoimmune disease in which probiotics appears to have an immune modulating action along with decreased inflammatory process. Therefore, we aim to investigate the efficacy of probiotics as an adjuvant therapy for rheumatoid arthritis. A comprehensive literature search was performed using nine databases including PubMed and Web of Science. Interesting data was extracted and meta-analyzed. We assessed the risk of bias using Cochrane Collaboration's tool. The protocol was registered in PROSPERO (CRD 42016036769). We found nine studies involving 361 patients who met our eligibility criteria. Our meta-analysis indicated that pro-inflammatory cytokine IL-6 was significantly lower in the probiotics compared with the placebo group (standardized mean difference = - 0.708; 95% confidence interval (CI) - 1.370 to 0.047, P = 0.036). However, there was no difference between probiotics and placebo in disease activity score (mean difference 0.023; 95% CI - 0.584 to 0.631, P = 0.940). Probiotics lowered pro-inflammatory cytokines IL-6 in RA; however, its clinical effect is still unclear. Hence, many high-quality randomized controlled trials (RCTs) are still needed to prove this effect.