Abstract: The present invention is directed to a particular arabinoxylan (“AX”) preparation and the finding that this preparation has a beneficial effect on the organization of the intestinal microbial community in the lumen and in particular at the site of the gut mucosa, where it modulates the barrier function of the intestinal surface, primarily by modulating the mucosa-associated microbial community towards a relative increase of health beneficial bacteria, such as bifidobacteria and lactobacilli. It is accordingly a first aspect of the present invention to provide said arabinoxylan preparation characterized in comprising isolated water-soluble arabinoxylans and the use thereof to improve functioning (e.g. barrier function) of the intestinal epithelium.