Impact ofβ2-1 fructan on faecal community change: results from a placebo-controlled, randomised, double-blinded, cross-over study in healthy adults

Abstract

AbstractHealthy adults (n30) participated in a placebo-controlled, randomised, double-blinded, cross-over study consisting of two 28 d treatments (β2-1 fructan or maltodextrin; 3×5 g/d) separated by a 14-d washout. Subjects provided 1 d faecal collections at days 0 and 28 of each treatment. The ability of faecal bacteria to metaboliseβ2-1 fructan was common; eighty-seven species (thirty genera, and four phyla) were isolated using anaerobic medium containingβ2-1 fructan as the sole carbohydrate source.β2-1 fructan altered the faecal community as determined through analysis of terminal restriction fragment length polymorphisms and 16S rRNA genes. Supplementation withβ2-1 fructan reduced faecal community richness, and two patterns of community change were observed. In most subjects,β2-1 fructan reduced the content of phylotypes aligning within theBacteroides, whereas increasing those aligning within bifidobacteria,Faecalibacteriumand the family Lachnospiraceae. In the remaining subjects, supplementation increased the abundance of Bacteroidetes and to a lesser extent bifidobacteria, accompanied by decreases within theFaecalibacteriumand family Lachnospiraceae.β2-1 Fructan had no impact on the metagenome or glycoside hydrolase profiles in faeces from four subjects. Few relationships were found between the faecal bacterial community and various host parameters; Bacteroidetes content correlated with faecal propionate, subjects whose faecal community contained higher Bacteroidetes produced more caproic acid independent of treatment, and subjects having lower faecal Bacteroidetes exhibited increased concentrations of serum lipopolysaccharide and lipopolysaccharide binding protein independent of treatment. We found no evidence to support a defined health benefit for the use ofβ2-1 fructans in healthy subjects.