Breath Gas Patterns Predict Response to Low FODMAP Diet

PHILADELPHIA — Non-fasting breath gas patterns may help identify patients with irritable bowel syndrome (IBS) who are most likely to respond to a low fermentable oligo-, di-, monosaccharides and polyols (FODMAP) diet, according to a new study.

The low FODMAP diet is the most evidence-based dietary therapy for patients with IBS, but we know that “only about 50% of our patients respond to it,” said principal investigator Prashant Singh, MD, assistant professor at the University of Michigan in Ann Arbor, Michigan. “Exhaled breath gases represent bacterial fermentation of dietary carbohydrates. These measurements could provide a simple biomarker for response to low FODMAP diets.”

Even before starting the low FODMAP diet, “you could see notable differences in breath test patterns between responders and nonresponders,” he said. “We saw that low FODMAP responders had higher hydrogen (H2) and lower methane (CH4) at baseline than nonresponders and had a greater drop in hydrogen following FODMAP restriction vs non-responders.”

He added that these results imply that responders to this diet may exhibit differences in baseline microbiota composition regarding saccharolytic capacity and/or methanogens. 

Singh presented the findings at the American College of Gastroenterology (ACG) 2024 Annual Scientific Meeting. 

Breaths That Can Predict Response

To determine if pre-intervention non-fasting breath patterns are associated with a clinical response to low FODMAP diets, Singh and colleagues enrolled 284 self-selected participants (mean age, 45.2 years) with mild to moderate gastrointestinal (GI) symptoms. Participants used an app-connected breath analyzer to record hourly, non-fasting H2 and CH4 levels during waking hours, in addition to logging meal content and symptom severity (bloating, abdominal pain, and flatulence) on a 0-10 scale. 

Patients were directed to consume their habitual diet for 1 week, before following an app-directed low FODMAP diet for 1 week. Responders were defined as those with a ≥ 30% reduction in at least one mean symptom score. The researchers then compared average hourly H2 and CH4 levels and symptom scores at baseline between low FODMAP diet responders and nonresponders.

Of the participants, 111 were classified as responders and 173 as nonresponders. There were no significant differences between the groups in gender, age, body mass index, or FODMAP per calorie.

Following FODMAP restriction, responders had consistently lower abdominal pain throughout the day and lower bloating and flatulence predominantly in the latter part of the day. Nonresponders experienced no significant changes in key abdominal symptoms after adopting the low FODMAP diet. 

The researchers found that breath tests taken at baseline revealed predictive trends between the groups, even though average FODMAP consumption did not significantly differ between them. Baseline H2 levels were higher among responders than among nonresponders, especially in the morning and evening. However, responders had lower baseline CH4 levels throughout the day. 

Following FODMAP restrictions, responders had a significant drop in non-fasting H2 but not CH4, whereas nonresponders did not have a significant drop in either.

The study was limited by the fact that participants were not clinically diagnosed with IBS, their GI symptoms were mild overall, and no data were available on stool consistency/frequency or fecal microbiome composition for correlation with exhaled breath gas levels.

A Potential New Biomarker

Session co-moderator Kyle Staller, MD, MPH, director of the Gastrointestinal Motility Laboratory at Mass General and associate professor of medicine at Harvard Medical School in Boston, Massachusetts, told Medscape Medical News that if validated, these findings provide hope for better directing low FODMAP diets to those patients who may benefit. 

There are some patients who may or may not respond to a FODMAP diet, for reasons we don’t yet know, possibly related to fermentation of gas, and it’s helpful to know before starting treatment, he said. It may help us with more of “a precision medicine approach before we really torture people with diets that can be very difficult to adhere to.” 

Staller, who was not involved in the study, added that, “People tend to really focus on small intestinal bacteria overgrowth when it comes to hydrogen and methane production, but in reality, this is really a very agile day-to-day, meal-to-meal responsiveness.” 

“It’s a different paradigm,” he continued. “I’d also like to see more data as to why we see the diurnal rhythm” and whether potential factors such as intestinal transit times are playing a role. 

Singh reported receiving royalties from UpToDate. Staller reported receiving research support from Ardelyx and Restasis and serving as a consultant to Anji, Ardelyx, GI Supply, Mahana, Restasis, and Sanofi. Funding associated with the study was not available at the time of publication. 

John Watson is a freelance writer in Philadelphia, Pennsylvania.