Colonic transit time is related to bacterial
metabolism and mucosal turnover in the gut
Henrik M. Roager1, Lea B. S. Hansen2, Martin I. Bahl1, Henrik L. Frandsen1, Vera Carvalho1,
Rikke J. Gøbel3, Marlene D. Dalgaard2, Damian R. Plichta2, Morten H. Sparholt4,
Henrik Vestergaard3, Torben Hansen3, Thomas Sicheritz-Pontén2, H. Bjørn Nielsen2,
Oluf Pedersen3, Lotte Lauritzen5, Mette Kristensen5, Ramneek Gupta2 and Tine R. Licht1
1National Food Institute, Technical University of Denmark, DK-2860 Søborg, Denmark. 2Department of Systems Biology, Technical University of Denmark,
DK-2800 Kgs. Lyngby, Denmark. 3The Novo Nordisk Foundation Center for Basic Metabolic Research, Section of Metabolic Genetics, University of
Copenhagen, DK-2200 København N, Denmark. 4Department of Radiology, Bispebjerg Hospital, DK-2400 København NV, Denmark. 5Department of
Nutrition, Exercise and Sport, University of Copenhagen, DK-1958 Frederiksberg C, Denmark.
Abstract
Little is known about how colonic transit time relates to human colonic metabolism and its importance for host health,
although a firm stool consistency, a proxy for a long colonic transit time, has recently been positively associated with gut
microbial richness. Here, we show that colonic transit time in humans, assessed using radio-opaque markers, is associated
with overall gut microbial composition, diversity and metabolism. We find that a long colonic transit time associates with
high microbial richness and is accompanied by a shift in colonic metabolism from carbohydrate fermentation to protein
catabolism as reflected by higher urinary levels of potentially deleterious protein-derived metabolites. Additionally,
shorter colonic transit time correlates with metabolites possibly reflecting increased renewal of the colonic mucosa.
Together, this suggests that a high gut microbial richness does not per se imply a healthy gut microbial ecosystem and
points at colonic transit time as a highly important factor to consider in microbiome and metabolomics studies.
Nature Microbiology, Published 27 June 2016, DOI: 10.1038/NMICROBIOL.2016.93