Plain language summary
Inulin is a water-soluble fibre present in chicory, onions, garlic, bananas and many other plants. It acts as prebiotic, passing through the small intestine into the colon where the fibres are fermented by the gut bacteria. This double-blind, randomised controlled cross-over intervention study aimed to assess the impacts of inulin supplementation on the diversity of intestinal bacterial profiles and on mild constipation in study participants. Modest effects of 12g of daily inulin consumption were detected on microbial composition and specific changes in the relative abundance were found for 3 particular bacterial species (Anaerostipes, Bilophila and Bifidobacterium). The reduction in the abundance of Bilophila was associated with reduced constipation and improved constipation-specific quality of life measures.
Abstract
OBJECTIVE Contrary to the long-standing prerequisite of inducing selective (ie, bifidogenic) effects, recent findings suggest that prebiotic interventions lead to ecosystem-wide microbiota shifts. Yet, a comprehensive characterisation of this process is still lacking. Here, we apply 16S rDNA microbiota profiling and matching (gas chromatography mass spectrometry) metabolomics to assess the consequences of inulin fermentation both on the composition of the colon bacterial ecosystem and faecal metabolites profiles. DESIGN Faecal samples collected during a double-blind, randomised, cross-over intervention study set up to assess the effect of inulin consumption on stool frequency in healthy adults with mild constipation were analysed. Faecal microbiota composition and metabolite profiles were linked to the study's clinical outcome as well as to quality-of-life measurements recorded. RESULTS While faecal metabolite profiles were not significantly altered by inulin consumption, our analyses did detect a modest effect on global microbiota composition and specific inulin-induced changes in relative abundances of Anaerostipes, Bilophila and Bifidobacterium were identified. The observed decrease in Bilophila abundances following inulin consumption was associated with both softer stools and a favourable change in constipation-specific quality-of-life measures. CONCLUSIONS Ecosystem-wide analysis of the effect of a dietary intervention with prebiotic inulin-type fructans on the colon microbiota revealed that this effect is specifically associated with three genera, one of which (Bilophila) representing a promising novel target for mechanistic research. TRIAL REGISTRATION NUMBER NCT02548247.
