Background and objectives: immune system alteration in irritable bowel syndrome (IBS) patients may be modulated by probiotics. We assessed the efficacy of some probiotic species in alleviating characteristic IBS symptoms.
Material and methods: a meta-analysis of all identified randomized controlled trials comparing probiotics with placebo in treating IBS symptoms was performed with continuous data summarized using standardized mean differences (SMDs) with 95% confidence intervals (95% CIs), where appropriate. The random-effects model was employed in cases of heterogeneity; otherwise, fixed-effects models were used.
Results: meta-analysis was performed with 10 of 24 studies identified as suitable for inclusion. Probiotics improved pain scores if they contained Bifidobacterium breve (SMD, - 0.34; 95% CI, - 0.66; -0.02), Bifidobacterium longum (SMD, -0.48; 95% CI, - 0.91; -0.06), or Lactobacillus acidophilus (SMD, -0.31; 95% CI, -0.61; -0.01) species. Distension scores were improved by probiotics containing B. breve (SMD, -0.45; 95% CI, -0.77; -0.13), Bifidobacterium infantis, Lactobacillus casei, or Lactobacillus plantarum (SMD, -0.53; 95% CI, -1.00; -0.06) species. All probiotic species tested improved flatulence: B. breve (SMD, -0.42; 95% CI, -0.75;- 0.10), B. infantis, L. casei, L. plantarum (SMD, -0.60; 95% CI, -1.07; -0.13), B. longum, L. acidophilus, Lactobacillus bulgaricus, and Streptococcus salivarius ssp. thermophilus (SMD, -0.61; 95% CI, -1.01; -0.21). There was not a clear positive effect of probiotics concerning the quality of life.
Conclusions: some probiotics are an effective therapeutic option for IBS patients, and the effects on each IBS symptom are likely species-specific. Future studies must focus on the role of probiotics in modulating intestinal microbiota and the immune system while considering individual patient symptom profiles.