• irritable bowel syndrome
• dietary fibre
• colonic fermentation

Consumption of dietary fibre has been associated with multiple beneficial outcomes. For example, it reduces the risk of cardiovascular disease by lowering cholesterol and improving glucose homeostasis, and it improves digestive comfort with looser and more frequent stools. Furthermore, dietary fibre can potentially lower the risk of colon cancer, although evidence from intervention studies supporting the latter is considered insufficient to serve as a basis of guidelines for dietary fibre intake.1 More recent studies indicate that dietary fibre also exhibits immunomodulatory properties and may affect mood and cognition.2

In addition to enhancing bulking in the colon and increasing the viscosity in the intestinal lumen, production of short-chain fatty acids by colonic microbial fermentation is believed to be an important mechanism underlying these health benefits.3 However, fermentation of dietary fibre concomitantly increases the production of gases, in particular hydrogen and to a lesser extent methane and carbon dioxide. Hydrogen primarily results from the reoxidation of reduced pyridine nicotinamide-adenine-dinucleotide (NADH) and flavine-adenine-dinucleotide (FADH) nucleotides, which is essential to maintaining the luminal redox balance. Accumulation of hydrogen, which would restrict further fermentation, is prevented by hydrogenotrophic microbes that convert hydrogen into acetate (acetogens), methane (methanogenic archaea) and sulfate (sulfate-reducing bacteria).4

Patients …