Colonic fermentation--more than meets the nose.

Fermentation of undigested foods in the colon by its resident bacteria affects not only colonic health (protection against inflammation and tumour formation) but also influences metabolic health. Studying fermentation directly is difficult for lack of access. We hypothesise that the anatomical structure of the colon is suited to act as a fermenting chamber with the gaseous molecules (VOCs) emitted having direct effects on the colonocytes as well as gut neural and metabolic effects. We refer to this complex system as the 'fermentome', and further hypothesise that alteration in the 'fermentome' through dietary modification will have a direct impact on colonic as well as metabolic health and disease. The VOCs emitted may play a role in bacterial chemical signalling within the colon but importantly could also function as a 'gas' biomarker. Measurement of such VOCs through non-invasive methods would have important application as a hypothesis-generating tool with subsequent clinical application.