Breath Test Study Reveals How Gut Gases Link to Digestive Symptoms

Authors
Journal
Journal of Clinical Gastroenterology
Year
DOI
10.1097/MCG.0000000000002326
Study Type
Human
Outcome
Neutral
Peer Reviewed
Yes
Country
United States
Health Condition
Small Intestinal Bacterial Overgrowth (SIBO)
Body System
Digestive System

TL;DR

In a large at-home breath test cohort, hydrogen sulfide levels were strongly associated with diarrhea and overall symptom severity, methane with constipation, and hydrogen with diarrhea.

Key Finding

Hydrogen sulfide levels in breath tests correlated most strongly with diarrhea, urgency, and abdominal pain, showing the greatest overall symptom severity compared to the other two gases measured.

Summary

Researchers analyzed breath test results from 3,004 people to see how three gases produced by gut bacteria relate to digestive symptoms. The study found that hydrogen sulfide (a gas produced by certain bacteria) was most strongly linked to diarrhea, urgency, and abdominal pain, while methane was associated with constipation. The type of sugar used in the test (lactulose versus glucose) also mattered—lactulose detected more cases of bacterial overgrowth than glucose did.

Practical Takeaway

This large real-world study suggests that three-gas breath testing may help identify which specific gut bacterial imbalances are driving a person's symptoms. However, the study only shows associations between gas levels and symptoms—it doesn't prove that reducing these gases would improve symptoms. The choice of substrate (lactulose versus glucose) in the test appears to affect results, which is important information for anyone considering this diagnostic test.

Abstract

Goals and background: Hydrogen (H2) breath testing (BT) is used to diagnose small intestinal bacterial overgrowth (SIBO), and methane (CH4) to diagnose constipation. Recently, a third microbially derived gas, hydrogen sulfide (H2S), was added to BT and associated with diarrhea. Here, we assess a 3-gas BT nationwide, comparing the results to gastrointestinal (GI) symptoms. Study: Consecutive subjects (N=6000) undergoing 3-gas at-home BT were asked to complete a symptom questionnaire. Substrate choice (glucose or lactulose) was at physician's discretion. H2, CH4, and H2S levels, and presence/absence of SIBO (≥20 ppm rise in H2 within 90 min), intestinal methanogen overgrowth (IMO) (≥10 ppm CH4), and intestinal sulfide overproduction (ISO, defined here as ≥2 ppm H2S) were compared with symptom severity. Gas interactions and symptoms' correlations were determined using machine learning (Uniform Manifold Approximation and Projection [UMAP]). Results: A total of 3004 subjects who completed breath tests and primary questions were included. Bloating was the most common reason for BT. More subjects reported severe or very severe symptoms for bloating (52.9%) than diarrhea (17.8%), constipation (17.1%), or abdominal pain (17.1%). SIBO positivity was more common using lactulose (27%) versus glucose (7.3%). Higher H2 levels correlated with more severe diarrhea (P=0.031), and CH4 levels correlated with constipation (P=0.002). Higher H2S levels correlated with more severe diarrhea (P<0.0001), urgency (P=0.003), and abdominal pain (P=0.01). UMAP revealed that H2S levels increased symptom severity, and ISO (alone or with SIBO/IMO) drove greater diarrhea, urgency, bloating, and overall severity, with highest pain and severity in ISO alone. Conclusions: H2, CH4, and H2S are associated with unique symptoms: CH4 with constipation and H2S with diarrhea and a greater overall symptom severity. Glucose appears less sensitive than lactulose, suggesting it could potentially miss some symptomatic patients.