SCFA Alterations in IBS Subtypes: Systematic Evidence and Future Prospects for Biomarker-Based Diagnosis in India

Irritable bowel syndrome (IBS) is a chronic disorder of gut-brain interaction characterized by abdominal pain and altered bowel habits. Short-chain fatty acids (SCFAs), microbial metabolites of dietary fiber, play key roles in gut physiology and have been implicated in IBS pathogenesis. Propionate, acetate, and butyrate are of particular interest as potential biomarkers for diagnosis and subtype differentiation. A systematic search of PubMed, Web of Science, and Embase identified studies reporting fecal SCFA concentrations in IBS patients versus healthy controls (HCs). Adult cohorts diagnosed by Rome criteria, case-control or randomized designs, and sufficient SCFA data for effect size calculation were included. Data were harmonized to mean ± SD and analyzed; pooled standardized mean differences (SMDs) with 95% confidence intervals (CI) were calculated, with subgroup analyses for IBS-D and IBS-C. Methodological quality was assessed using the Newcastle-Ottawa Scale (NOS). Eleven studies met inclusion criteria. Across all IBS cohorts, propionate was significantly elevated compared to HCs, while acetate and butyrate showed no differences. In IBS-D, propionate was consistently higher. In IBS-C, total SCFAs were significantly reduced, with negligible heterogeneity. Acetate, propionate, and butyrate remained non-significant, with moderate to substantial heterogeneity. NOS assessment indicated that most studies were of good quality, with one rated moderate. This meta-analysis highlights propionate elevation as a biomarker for IBS, particularly IBS-D, and reduced total SCFAs as a distinct metabolic signature in IBS-C. Variability in individual metabolites reflects dietary and methodological influences. The absence of Indian cohorts limits generalizability; future studies integrating SCFA profiling with microbiome analysis in Indian populations are needed to validate biomarker utility and support precision management of IBS.