Different Types of SIBO Show Unique Gut Bacteria and Metabolism Patterns

Authors
Journal
Nature Scientific Reports
Year
DOI
10.1038/s41598-026-43935-5
Study Type
Human
Outcome
Neutral
Peer Reviewed
Yes
Country
China
Health Condition
Small Intestinal Bacterial Overgrowth (SIBO)
Body System
Digestive

TL;DR

Hydrogen- and methane-predominant SIBO subtypes show distinct clinical features and microbiome–metabolome profiles, with methane levels better differentiating subtypes.

Key Finding

Hydrogen- and methane-predominant SIBO subtypes show distinct clinical characteristics and different bacterial and metabolic profiles, with methane measurements being more useful than hydrogen measurements for telling the subtypes apart.

Summary

This study examined 503 adults who underwent breath testing to detect small intestinal bacterial overgrowth (SIBO)—a condition where bacteria grow excessively in the small intestine. Researchers compared people with different types of SIBO based on whether they produced more hydrogen or methane gas. They found that hydrogen-predominant and methane-predominant SIBO types had different clinical features, different bacterial compositions in their stool, and different metabolic signatures (patterns of chemical compounds). The study suggests these two SIBO subtypes may involve distinct interactions between the person's body and their bacteria.

Practical Takeaway

This exploratory research identifies biological differences between SIBO subtypes, which may eventually help doctors tailor treatments. However, the study was observational and the multi-omics findings (microbiota and metabolic data) were limited to a subset of participants, so these results are preliminary. More research is needed before these differences can guide clinical decisions for individual patients.

Abstract

We aimed to investigate the clinical, microbiome, and metabolomic characteristics of hydrogen (H₂)- and methane (CH₄)-predominant small intestinal bacterial overgrowth (SIBO) subtypes. We retrospectively enrolled adults who underwent standardized lactulose hydrogen–methane breath testing between February 2021 and July 2025. Participants were categorized as Normal, H₂–SIBO, CH₄–SIBO, or mixed H₂/CH₄–SIBO. Clinical characteristics were compared using Kruskal–Wallis tests and chi-square tests. Multivariable logistic regression was used to identify factors independently associated with each SIBO subtype. Expiratory gas profiles (AUC, peak, and mean values) were quantified, and correlations with age and body mass index (BMI) were assessed using Spearman analysis. In a subset of participants, stool samples underwent 16S rRNA gene sequencing and untargeted metabolomic profiling, followed by integrative analyses of microbiota composition, diversity, and metabolic signatures across SIBO subtypes. Among 503 participants, higher serum albumin levels were independently associated with H₂–SIBO, whereas higher fasting glucose was independently associated with CH₄–SIBO. Breath-test profiling indicated that methane parameters, rather than hydrogen, better differentiated SIBO subtypes, and total (H₂ + CH₄) gas output was modestly correlated with age but not BMI. In the exploratory multi-omics subset, fecal microbiota composition and metabolomic signatures differed by subtype; LEfSe identified Bacteroidaceae as a CH₄-SIBO signature and Alcaligenaceae/Acidaminococcaceae as H₂–SIBO signatures. Differential metabolites were enriched in pathways related to branched-chain amino acid biosynthesis, lipid metabolism, and mineral absorption. H₂- and CH₄-predominant SIBO subtypes exhibit distinct clinical correlates and stool microbiome–metabolome profiles. Methane exhalation appears more informative for differentiating subtypes, and age is modestly associated with total expiratory gas volumes. These findings support potential subtype-specific host–microbe metabolic interactions, although the multi-omics results should be interpreted as exploratory.