The meta-analysis of randomized controlled trials on the effect of probiotics on immune factors in patients with inflammatory bowel disease (IBD)

Clinical trials on probiotic treatment for IBD have reported conflicting changes in immune factor levels. To resolve this discrepancy, we systematically reviewed randomized controlled trials to better understand how probiotics influence serum immune markers in individuals with IBD. We searched PubMed, the Cochrane Library, Web of Science, and Embase to identify relevant studies published until November 2025. Inflammatory cytokine levels served as our primary endpoint measure. Two authors independently conducted the literature screening, bias risk appraisal, and information extraction procedures. For all included studies, outcome measures were systematically extracted and analyzed. Quantitative synthesis was conducted by calculating standardized mean differences (SMDs) with 95% confidence intervals (CIs), while heterogeneity was assessed using the I 2 statistic. A random-effects model was employed for all meta-analyses to account for potential between-study variations. A total of 3,081 studies were screened, with 10 RCTs meeting inclusion criteria for meta-analysis. Probiotics can reduce CRP levels (SMD = −1.11; 95% CI = [−1.93, −0.29], I 2 = 92.2%, p < 0.001) to alleviate IBD symptoms, significantly lower TNF- α levels ( SMD = −2.31; 95% CI = [−3.67, −0.95], I 2 = 98.6%, p < 0.001), and increase IL-10 levels (SMD = 1.82; 95% CI = [0.52, 3.13], I 2 = 98.1%, p < 0.001). However, their regulatory effect on IL-6 (SMD = 0.44, 95% CI = [−1.59, 2.46], I 2 = 98.7%, p < 0.001) was not statistically significant. In the treatment of IBD, probiotic supplementation can bidirectionally modulate pro-inflammatory and anti-inflammatory cytokines, significantly reducing serum concentrations of TNF- α and CRP, while increasing IL-10 levels, demonstrating its potential therapeutic efficacy in IBD treatment. • Assesses the impact of probiotic supplementation on serum immune biomarkers (TNF- α , IL-16, IL-10, CRP) in IBD patients. • Demonstrates the modulation of both pro- and anti-inflammatory cytokine levels. • Uses the GRADE framework to evaluate the certainty of evidence, supporting the validity of the results.