Detection of changes in regional colonic fermentation in response to supplementing a low FODMAP diet with dietary fibres by hydrogen concentrations, but not by luminal pH

Carbohydrate fermentation plays a pivotal role in maintaining colonic health with excessive proximal and deficient distal fermentation being detrimental.To utilise telemetric gas- and pH-sensing capsule technologies for defining patterns of regional fermentation following dietary manipulations, alongside conventional techniques of measuring fermentation.In a double-blind crossover trial, 20 patients with irritable bowel syndrome were fed low FODMAP diets that included no extra fibre (total fibre content 24 g/day), or additional poorly fermented fibre, alone (33 g/day) or with fermentable fibre (45 g/day) for 2 weeks. Plasma and faecal biochemistry, luminal profiles defined by tandem gas- and pH-sensing capsules, and faecal microbiota were assessed.Plasma short-chain fatty acid (SCFA) concentrations (μmol/L) were median (IQR) 121 (100-222) with fibre combination compared with 66 (44-120) with poorly fermented fibre alone (p = 0.028) and 74 (55-125) control (p = 0.069), but no differences in faecal content were observed. Luminal hydrogen concentrations (%), but not pH, were higher in distal colon (mean 4.9 [95% CI: 2.2-7.5]) with fibre combination compared with 1.8 (0.8-2.8) with poorly fermented fibre alone (p = 0.003) and 1.9 (0.7-3.1) control (p = 0.003). Relative abundances of saccharolytic fermentative bacteria were generally higher in association with supplementation with the fibre combination.A modest increase in fermentable plus poorly fermented fibres had minor effects on faecal measures of fermentation, despite increases in plasma SCFA and abundance of fermentative bacteria, but the gas-sensing capsule, not pH-sensing capsule, detected the anticipated propagation of fermentation distally in the colon. The gas-sensing capsule technology provides unique insights into localisation of colonic fermentation.ACTRN12619000691145.