Probiotic Therapy of the Irritable Bowel Syndrome: Why Is the Evidence Still Poor and What Can Be Done About It?

Abstract

Background/AimsDespite numerous randomized clinical trials and meta-analyses, there is no increased evidence for the efficacy of probiotics in the treatment of irritable bowel syndrome (IBS). We review this evidence, identify and analyse the reasons for this lack of evidence and propose methodological improvements for future studies. MethodsBased on a literature search, we identified 56 papers that matched the purpose of our analyses. Twenty-seven studies used multi-species bacterial preparations and 29 used single-strain probiotics. They were analysed regarding patients included, treatment duration, probiotic dosage, and outcome measures. ResultsTrials in both groups suffered from heterogeneity with respect to probiotic concentration, duration of treatment, and other methodological issues (crossover design and underpowered studies). This heterogeneity did not allow the application of a meta-analytic approach and a systematic review was therefore performed instead. Multi-strain preparations combined 2 to 8 different bacterial subspecies, mostly lactobacilli or bifidobacteria, and used variable lengths of treatments. Overall, more than 50% of trials presented negative outcomes. The majority of the single-strain probiotic trials employing lactobacilli or Saccharomyces were negative, whereas trials employing bifidobacteria showed positive results. ConclusionsThe heterogeneity of the studies of probiotics in IBS questions the value of meta-analyses. The use of different bacterial strains and different mixtures of these strains, as well as different dosages, are the main contributors to this heterogeneity. Current data provides limited evidence for the efficacy of a small number of single-strain probiotics in IBS (mostly bifidobacteria) and

Effect of Probiotics on Central Nervous System Functions in Animals and Humans: A Systematic Review

“…To date, there are a few reviews on probiotic effects on infantile colic, which may reflect peripheral nervous system action, and one recent study reviewing only human studies. [64][65][66] Similarly, among the 56 RCTs so far which tested probiotics in adults with IBS that have or have not shown effects on peripheral (bowel) functions, 15 none have investigated whether any CNS effect was affected or improved. We identified studies applying probiotics as single-or multiple-strain preparations in animals and humans.…”

“…The clinical efficacy of probiotic interventions and guidelines for their administration in diseases such as diarrhea, allergies, IBS, and inflammatory bowel disease has been addressed in previous reviews. 15,71,72 More studies investigating probiotic effects in mental disorders are needed.…”

“…[67][68][69] These probiotics were also found to reduce the symptoms of gastrointestinal disease, such as irritable bowel syndrome. 15,16,58,70 Probiotics may play an important role in gut-brain axis communication, thereby benefiting both the brain and the gut. While some studies found no significant effect of probiotic intervention, the evidence is inadequate to conclude that the interventions were ineffective because some difficulties and/or weak points exist.…”

Irritable bowel syndrome

“…However, a central effect of 5-HT3 receptor antagonists on pain cannot be excluded 200 . Safety concerns, with 183,184,205 ; again, it is unclear whether probiotics act on IBS symptoms through direct modulation of the microbiota, indirect via the gut immune system or otherwise.Others-A proportion of patients use herbal supplements either as single herbs or in combination. Four weeks of treatment with iberogast, which is a mixture of nine plant extracts, improved abdominal pain and QOL in a double-blind RCT of 208 patients with all types of IBS 206 .…”

Irritable Inflammatory Bowel Syndrome as a Distinct Disease Entity

“…Amitriptyline and selective serotoninreuptake inhibitors are effective for treating psychological symptoms in IBD patients. 10 The evidence of probiotic therapy for IBS is still poor because of insufficient efficacy of current data, 11 and therefore, probiotic therapy for IIBS is still questionable. This was a retrospective cross sectional study, therefore, it would not be expected if initial disease severity correlated with development of IBS-like symptoms during clinical course.…”