Impact of Short Duration FODMAP Restriction on Breath Gases and Gastrointestinal Symptoms.

Background and aims: IBS symptoms are thought to relate in part to the accumulation of luminal gases following ingestion of fermentable carbohydrates (i.e. FODMAPs). To understand this relationship, participants monitored breath hydrogen (H2) and methane (CH4) levels using an at-home breath analysis device and recorded symptoms and meals in real-time using the associated app.

Methods: We studied 1,984 users from July 2021 to April 2025. Participants first completed a baseline week on their habitual diet, followed by a one-week low FODMAP diet ("Reset"), with continued tracking of meals, symptoms, and post-prandial H2 and CH4 levels. Breath H2 and CH4 were measured in parts per million (PPM), and area under the curve (AUC) was calculated to assess gas production during typical waking hours. Participants recorded dietary intake and gastrointestinal symptoms after meals (i.e. non-fasting).

Results: Breath H2, CH4, and gastrointestinal symptoms (bloating, abdominal pain, and flatulence) were significantly reduced following FODMAP restriction (all p < 0.0001). Both mild/absent and moderate/severe symptom groups showed significant improvements in symptoms with greater absolute reductions seen in the moderate/severe group. Exhaled gas levels, particularly H2, exhibited diurnal variation corresponding to mealtimes and symptom patterns.

Conclusion: This study suggests that breath H2 and CH4 may be influenced by short-term dietary changes and could be a useful biomarker of response to FODMAP restriction. Future studies should investigate whether non-fasting breath H2 and CH4 levels, in response to habitual dietary intake, is predictive of response to the low-FODMAP diet.