High dose of prebiotics reduces fecal water cytotoxicity in healthy subjects

Scope: In vitro and animal studies have shown differential colonic fermentation of structurally different prebiotics. We evaluated the impact of two structurally different prebiotics (wheat bran extract (WBE, containing arabinoxylan-oligosaccharides) and oligofructose) on colonic fermentation and markers of bowel health in healthy volunteers. Methods and results: Nineteen healthy subjects completed a double-blind, cross-over randomized controlled trial. Interventions with WBE, oligofructose or placebo for 2 wk (week 1: 15 g/day; week 2: 30 g/day) were separated by 2-wk wash-out periods. At the end of each study period, colonic fermentation was characterized through a metabolomics approach. Fecal water genotoxicity and cytotoxicity were determined using the comet and WST-1 assay, respectively, as parameters of gut health. Cluster analysis revealed differences in effects ofWBE and oligofructose on colonic fermentation. WBE, but not oligofructose, reduced fecal p-cresol (p=0.009) and isovaleric acid concentrations (p=0.022), markers of protein fermentation. Fecal water cytotoxicity was significantly lower after intake ofWBE (p=0.015). Both WBE- and oligofructose-intake tended to reduce fecal water genotoxicity compared to placebo (WBE: p = 0.060; oligofructose: p = 0.057). Changes in fermentation were not related to changes in fecal water toxicity. Conclusion: Structurally different prebiotics affect colonic fermentation and gut health in a different way.