Breath Test Identifies Bacterial Overgrowth Subtypes in Bloating Patients
- Authors
- Congcong Jin, Ruiping Liu, Zongyao Ling, Chuanlian Chu
- Journal
- Journal of Visualized Experiments (JoVE)
- Year
- 2026
- DOI
- 10.3791/71610
- Study Type
- Human
- Outcome
- Neutral
- Peer Reviewed
- Yes
- Country
- China
- Health Condition
- Functional Bloating
- Body System
- Gastrointestinal
TL;DR
Hydrogen-methane breath testing identified distinct gas-production patterns in functional bloating, with positive tests linked to greater bloating severity and methane more strongly associated with constipation.
Key Finding
Adults with functional bloating who tested positive for abnormal hydrogen or methane gas production had greater bloating severity, and methane-positive patients were more likely to experience constipation-related symptoms than hydrogen-positive patients.
Summary
This study looked at whether a breath test measuring hydrogen and methane gases could help identify different subtypes of patients with functional bloating (chronic bloating without a clear structural cause). Ninety adults with functional bloating took a standardized breath test after drinking lactulose, a sugar that gut bacteria ferment. Researchers found that about half tested positive for abnormal gas production, and those who did had more severe bloating. Different gas patterns — hydrogen, methane, or both — were linked to different bowel habits, suggesting the breath test can reveal meaningful differences between patients.
Practical Takeaway
This study is about measuring hydrogen gas produced by gut bacteria — not hydrogen water consumption — so it does not directly apply to people interested in drinking hydrogen water. However, it highlights that hydrogen gas in the gut plays a measurable role in bloating and digestive symptoms, which is relevant background for understanding gut-related hydrogen research.
Abstract
Functional bloating is a common disorder of gut-brain interaction with heterogeneous symptom patterns and uncertain underlying mechanisms. Small intestinal bacterial overgrowth and intestinal methanogen overgrowth have both been implicated in gas-related symptoms; however, the clinical utility of combined lactulose hydrogen-methane breath testing for phenotypic characterization in patients with functional bloating remains incompletely defined. This cross-sectional observational study evaluated whether lactulose hydrogen-methane breath testing could distinguish clinically relevant subgroups among symptomatic patients with functional bloating. Ninety adults with functional bloating underwent standardized lactulose hydrogen-methane breath testing with serial sampling over 120 min. Demographic characteristics, symptom duration, bloating severity, abdominal pain, bowel habit patterns, and breath gas profiles were recorded. Breath test results were categorized as hydrogen-positive, methane-positive, mixed-positive, or negative according to predefined interpretation criteria. Breath testing was positive in 42 of 90 patients, including 24 hydrogen-positive, 12 methane-positive, and 6 mixed-positive cases. Patients with positive breath tests exhibited greater bloating severity than those with negative breath tests. Methane-positive and mixed-positive groups demonstrated a higher prevalence of constipation-related features, whereas the hydrogen-positive group showed greater overlap with mixed bowel habits. These findings demonstrate that combined lactulose hydrogen-methane breath testing can identify clinically meaningful gas-production phenotypes in adults with functional bloating and may support symptom-based clinical stratification.