Editorial: The importance of systematic reviews and meta-analyses of probiotics and prebiotics.

Irritable bowel syndrome (IBS) and chronic idiopathic constipation are prevalent and burdensome gastrointestinal disorders. A systematic review and meta-analysis of the evidence for probiotics, prebiotics, and synbiotics in IBS and chronic idiopathic constipation has recently been performed. By far, the most convincing evidence was for the use of probiotics in IBS, which reported that overall probiotics reduced the risk of symptom persistence by 21%. However, only a minority of the trials were at a low risk of bias, and some used small sample sizes. Meta-analysis is a powerful tool to combine individual small trials to improve the power to detect the direction, size, and consistency of an effect, but it can do little to overcome the poor design of individual trials. Many debate the use of meta-analysis to combine data from different probiotic species, strains, or combinations. It is recommended that all future meta-analyses of probiotics, in any clinical setting, perform subgroup analysis on specific species/strains and specific combinations. It is hoped that the current meta-analysis will empower clinicians in making evidence-based decisions regarding whether probiotics should be recommended for IBS, which species/strain(s) to use, and for which symptoms.