The Utility of Probiotics in the Treatment of Irritable Bowel Syndrome: A Systematic Review

Purpose: To perform a systematic review of randomized controlled trials (RCTs) evaluating the efficacy, safety and tolerability of probiotics in the treatment of IBS. Methods: Searches of MEDLINE, PUBMED, EMBASE and COCHRANE databases were performed to identify appropriate studies. Study selection criteria: (1) study design-randomized controlled trials (RCT),; (2) study population-adults with IBS defined by Manning or Rome II criteria;, (3) intervention-single or combination probiotic versus placebo; (4) outcome-improvement in IBS symptoms and frequency of adverse events. Data about quality of study design based upon Rome Committee recommendations was also extracted. Data were extracted in duplicate. Due to extreme variability in study design, study dosage, and outcome measures, quantitative pooling of data was not feasible. Results: 13 RCTs met selection criteria. 11/13 studies demonstrated sub-optimal study design with inadequate blinding, inadequate trial length, inadequate sample size, and lack of ITT analysis. Only three studies provided any quantifiable data about tolerability and adverse events. The only probiotic to demonstrate significant improvement in IBS symptoms in appropriately designed studies was Bifidobacterium infantis 35624 (Align ®, Proctor & Gamble). In the first, Bifidobacterium infantis 35624 resulted in significant improvement in the composite score abdominal pain/discomfort, bloating/distention and bowel movement difficulty compared to placebo for the entire treatment period (P < 0.05). In a subsequent study, Bifidobacterium infantis 35624 again demonstrated superior efficacy to placebo for the primary outcome measure abdominal pain/discomfort as well as the secondary measures bloating/distention, incomplete evacuation, straining, passage of gas and a composite score of abdominal pain/discomfort, bloating/distention, and bowel movement satisfaction at the a priori time point four weeks. Conclusion:Bifidobacterium infantis 35624 has demonstrated efficacy for improvement in IBS symptoms. There is inadequate data to comment on the efficacy of other probiotics. Most trials do not provide adequate data about safety and tolerability. Future RCTs should follow Rome recommendations for appropriate design of an RCT and should provide precise data on tolerability and adverse events.