Title : Consistency, clinical Relevance, and limitations of gut microbiota findings in irritable bowel syndrome: A review of 20 studies
Abstract:
Background: Irritable bowel syndrome (IBS) is a prevalent functional gastrointestinal disorder with multifactorial pathogenesis. Increasing evidence links IBS to gut microbiota alterations; however, findings remain heterogeneous and clinical translation is challenging.
Aim: To evaluate the consistency, clinical relevance, and methodological limitations of reported gut microbiota alterations in IBS by analyzing 20 peer-reviewed studies, and to compare the effectiveness of microbiota-targeted interventions.
Methods: A narrative comparative review of 20 peer-reviewed studies (including observational studies, randomized controlled trials, and meta-analyses) was conducted. The analysis focused on: 1) microbiota patterns in IBS vs. healthy controls; 2) intervention outcomes (low-FODMAP diet, probiotics/synbiotics, fecal microbiota transplantation (FMT)); and 3) sources of heterogeneity across studies.
Results: Across studies, no single reproducible microbial signature of IBS was identified. Reported alterations frequently included reduced microbial diversity and functional shifts involving short-chain fatty acid-related pathways, but results varied by IBS subtype, population, and sequencing methodology. Low-FODMAP diet was consistently associated with symptom improvement, yet may reduce beneficial taxa such as Bifidobacterium; probiotic co-administration may partially restore these changes in some cohorts. Meta-analyses suggest probiotics provide modest symptom improvement, but effects appear strain-, dose-, and subtype-dependent. FMT outcomes were inconsistent, with response influenced by donor selection and administration route; microbiota changes did not reliably translate into sustained clinical benefit and adverse effects were reported.
Conclusion: Current evidence supports an association between gut microbiota and IBS, but heterogeneity and methodological variability limit reproducibility and causal interpretation. Standardized study designs, subtype-stratified analyses, and long-term follow-up are needed to define clinically actionable microbiome-based biomarkers and optimize personalized interventions.
Keywords: IBS; gut microbiota; dysbiosis; low-FODMAP; probiotics; fecal microbiota transplantation.
