Gut Microbiome Composition and Function, Diet, and Clinical Factors in Relation to Fermentable Carbohydrate-Induced Bloating: A Double-Blind, Randomized, Crossover Trial.

In 30 seconds

This double-blind, placebo-controlled, randomized crossover trial examined clinical, dietary, microbial, and fermentation factors associated with bloating after fermentable carbohydrates in people with functional bloating. Participants received 8 g/d of fructan or α-galacto-oligosaccharides (α-GOS) for 7 days, with a 21-day washout. Of those completing both challenges, 7/39 (17.9%) responded to fructan and 8/40 (20%) to α-GOS, experiencing fiber-related symptom induction. Greater abdominal girth distinguished responders to both challenges; higher prechallenge breath hydrogen was also associated with response to α-GOS.

Key findings

• Fructan-related symptom induction occurred in 7/39 participants (17.9%); α-GOS-related induction occurred in 8/40 (20%).
• Greater abdominal girth distinguished responders from nonresponders to fructan (P = 0.009) and α-GOS (P = 0.030).
• α-GOS responders had higher prechallenge breath hydrogen than nonresponders (P = 0.011).
• Fructan responders had higher carbohydrate-active enzyme diversity, while α-GOS responders showed a greater increase in gene expression for GABA degradation.

Why it matters

The findings suggest that baseline symptom burden and, for α-GOS, breath hydrogen may help explain why some people with functional bloating experience symptom worsening with fermentable fibers. Microbial functional measures also differed between response groups, but the study does not establish their role in causing symptoms. These observations may inform further work on individual variation in food-related bloating.

What to keep in mind

The trial included 41 participants, with 39 completing both challenges. Microbial findings were exploratory, and the authors state that further investigation is needed before drawing firm conclusions about microbial influence.