DIETARY FRUCTOOLIGOSACCHARIDE, XYLOOLIGOSACCHARIDE AND GUM-ARABIC HAVE VARIABLE EFFECTS ON CECAL AND COLONIC MICROBIOTA AND EPITHELIAL-CELLPROLIFERATION IN MICE AND RATS

Two experiments were conducted to determine if supplementing soluble f iber (fructooligosaccharide, xylooligosaccharide or gum arabic) to a s emielemental diet would beneficially change cecal and colonic microbio ta populations and enhance epithelial cell proliferation. Experiments 1 and 2 used identical dietary regimens; mice and rats were given free access to a powdered semi-elemental diet. Animals were assigned to on e of the four following treatment groups: control, no supplemental die tary fiber, fructooligosaccharide, xylooligosaccharide and gum arabic. Dietary fiber was supplied via drinking water at 30 g/L. In Experimen t 1 populations of Bifidobacteria and total anaerobic flora were enume rated from the contents of the cecum and colon of weanling mice. Consu mption of fructooligosaccharide increased (P < 0.05) the concentration s of Bifidobacteria and the, ratio of Bifidobacteria to total anaerobi c flora. In Experiment 2 tissue from the cecum and distal colon of wea nling rats was examined for morphological changes of the mucosa. Consu mption of xylooligosaccharide increased (P < 0.05) cecal crypt depth a nd labeling index relative to the other three treatments. Consumption of gum arabic and the control diet increased (P < 0.01) cecal prolifer ation zone. Consumption of xylooligosaccharide and the control diet in creased (P < 0.01) cecal cell density (number of cells in a vertical-h alf of the crypt). Distal colonic crypt depth was greatest (P < 0.05) in controls and rats fed fructooligosaccharide, intermediate in those fed gum arabic, and smallest in those fed xylooligosaccharide. These r esults suggest that fructooligosaccharide effectively stimulates growt h of Bifidobacteria and xylooligosaccharide supports a modest enhancem ent of cecal epithelial cell proliferation.