Breath Test Study Reveals How Gut Gases Link to Digestive Symptoms
- Authors
- Mark Pimentel, Gabriela Leite, LiJin Joo, Ali Rezaie, Ruchi Mathur, Darren Brenner, Linda Nguyen, Mohamad Rashid, Ava Hosseini, Daniel Brimberry, Matthew Mitcho, David Richardson, Fabrice Wilfong
- Journal
- Journal of Clinical Gastroenterology
- Year
- 2026
- 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 (excerpt)
Goals and Background: Hydrogen (H 2 ) breath testing (BT) is used to diagnose small intestinal bacterial overgrowth (SIBO), and methane (CH 4 ) to diagnose constipation. Recently, a third microbially derived gas, hydrogen sulfide (H 2 S), was added to BT and associated with diarrhea. Here, we…