Effect of multistrain probiotics on symptom severity in irritable bowel syndrome: a systematic review and meta-analysis of irritable bowel syndrome–symptom severity score outcomes

Irritable bowel syndrome (IBS) is a common gastrointestinal disorder with varying symptom severity. Although probiotics are frequently used for IBS management, the effects of multistrain probiotic interventions on IBS symptom severity, as measured by the IBS symptom severity score (IBS-SSS), remain unclear. This systematic review, conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020 guidelines, compared multistrain probiotics with placebo in patients with IBS, focusing on IBS-SSS outcomes. Risk of bias was assessed using the Risk of Bias 2.0 tool, and meta-analysis was performed with Review Manager 5.4.1. From the 1858 screened records, 12 studies involving 1303 participants were included. Multistrain probiotics significantly reduced total IBS-SSS scores [mean difference = -43.66, 95% confidence interval (CI): -65.89 to -21.44, P = 0.0001, I ² = 99%]. Significant improvements were also found in IBS-SSS subscores, including number of days with pain (mean difference = -7.38, 95% CI: -11.86 to -2.89, P = 0.001, I ² = 100%), bloating (-5.62, 95% CI: -10.76 to -0.48, P = 0.03, I ² = 100%), bowel habit satisfaction (-11.90, 95% CI: -19.21 to -4.59, P = 0.001, I ² = 99%), and quality of life (QoL) (-11.99, 95% CI: -16.3 to -7.60, P < 0.00001, I ² = 91%); however, changes in abdominal pain scores and IBS-specific QoL were not statistically significant. High heterogeneity prompted sensitivity analyses to identify contributing factors. Overall, multistrain probiotics significantly reduced IBS-SSS and its subscores but did not significantly improve QoL compared with placebo.