Systematic Review With Meta-analysis

The Efficacy of Prebiotics, Probiotics, Synbiotics and Antibiotics in Irritable Bowel Syndrome

Alexander C. Ford; Lucinda A. Harris; Brian E. Lacy; Eamonn M. M. Quigley; Paul Moayyedi


Aliment Pharmacol Ther. 2018;48(10):1044-1060. 

In This Article

Abstract and Introduction


Background: Irritable bowel syndrome (IBS) is a chronic functional bowel disorder. Disturbances in the gastrointestinal microbiome may be involved in its aetiology.

Aim: To perform a systematic review and meta-analysis to examine the efficacy of prebiotics, probiotics, synbiotics and antibiotics in IBS.

Methods: MEDLINE, EMBASE, and the Cochrane Controlled Trials Register were searched (up to July 2017). Randomised controlled trials (RCTs) recruiting adults with IBS, comparing prebiotics, probiotics, synbiotics or antibiotics with placebo or no therapy were eligible. Dichotomous symptom data were pooled to obtain a relative risk (RR) of remaining symptomatic after therapy, with a 95% confidence interval (CI). Continuous data were pooled using a standardised mean difference with a 95% CI.

Results: The search identified 4017 citations. Data for prebiotics and synbiotics were sparse. Fifty-three RCTs of probiotics, involving 5545 patients, were eligible. Particular combinations of probiotics, or specific species and strains, appeared to have beneficial effects on global IBS symptoms and abdominal pain, but it was not possible to draw definitive conclusions about their efficacy. There were five trials of similar design that used rifaximin in non-constipated IBS patients, which was more effective than placebo (RR of symptoms persisting = 0.84; 95% CI 0.79–0.90). Adverse events were no more common with probiotics or antibiotics.

Conclusions: Which particular combination, species or strains of probiotics are effective for IBS remains, for the most part, unclear. Rifaximin has modest efficacy in improving symptoms in non-constipated IBS.


Irritable bowel syndrome (IBS) is a functional bowel disorder with a relapsing and remitting natural history.[1–3] The global prevalence of the condition in the community is approximately 10%, depending on the criteria used to define its presence,[4] although using the latest Rome IV criteria it is lower, estimated at 6%.[5] Despite being common, only a minority of people who report symptoms suggestive of IBS will consult a physician.[3] Because the pathophysiology of the disorder remains incompletely understood, medical treatment is empirical and is usually based on targeting the predominant symptom reported by the patient.[6] This leads to unsatisfactory control of symptoms for many patients and, therefore, alternative approaches are needed.

The concept that alterations in the gut microbiome might be relevant to IBS arose from observations that symptoms of IBS often developed after an infection, known as post-infectious IBS.[7,8] Furthermore, small intestinal bacterial overgrowth (SIBO) may cause symptoms indistinguishable from IBS,[9] and data suggest that the colonic microbiome is altered in patients with IBS, when compared with healthy controls.[10–13] In addition, some IBS symptoms, such as bloating, slowed gastrointestinal (GI) transit, and early satiety have been associated with specific gut microbiome profiles.[14,15]

Data from studies such as these suggest that alterations in the gut microbiome may induce IBS symptoms de novo or exacerbate existing symptoms. This then raises the obvious question of whether antibiotics, or other related interventions, can be used to modulate the gut microbiome and thus improve IBS symptoms. Prebiotics are substrates that are selectively utilised by host microorganisms, conferring a health benefit.[16] Probiotics have been defined as "live microorganisms that, when administered in adequate amounts, confer a health benefit on the host".[17] Synbiotics, which are also food or dietary supplements, are a mixture of probiotics and prebiotics that act synergistically to promote the growth and survival of beneficial organisms.

The use of antibiotics as a means of treating SIBO, a postulated pathophysiologic mechanism for IBS, remains an area of continuing controversy. This is because the tests commonly used to diagnose SIBO, such as lactulose and glucose hydrogen breath tests and small intestinal aspirates, are fraught with problems such as altered intestinal transit,[18–20] which influence their sensitivity and specificity. Despite the fact that any effect of probiotics in IBS is poorly understood, a recent survey of clinicians demonstrated that most believe probiotics to be a benign therapy and over 90% incorporated probiotics into their clinical practice.[21] Gaining a better understanding of probiotics and their clinical use in IBS remains a challenging task due to variations in study design, strain, species and dose of probiotics as well as small size of study populations.

Previous systematic reviews by our group,[22,23] conducted to inform the American College of Gastroenterology's (ACG) monograph on the management of IBS,[24,25] have examined the role of prebiotics, probiotics and synbiotics, but not antibiotics, in IBS. In the intervening 4 years since our last meta-analysis, there have been further studies published. We therefore performed an updated systematic review and meta-analysis to examine the efficacy of prebiotics, probiotics, synbiotics and antibiotics in IBS.