THE EFFECTS OF AND INTERACTIONS BETWEEN FERMENTABLE DIETARY FIBER ANDLIPID IN GERM-FREE AND CONVENTIONAL MICE

Background/Aims: Dietary fiber can stimulate intestinal epithelial cel l proliferation. The aim of this study was to resolve the different ro les of fermentation and intraluminal viscosity on this trophic action and to investigate reported interactions between fiber and dietary fat . Methods: Conventional and germfree mice were fed guar gum in combina tion with low- or high-lipid diets for 2 weeks, and crypt cell product ion rates were determined. Results: Guar gum significantly stimulated proliferation in the small intestine, especially when combined with fa t. Lipid itself also stimulated proliferation in the small intestine a nd had a direct trophic effect in the cecum and colon of the germfree mice. Fiber markedly stimulated proliferation in the cecum and colon b ut only in the conventional group. Interactions between lipid and bact eria and between guar gum and bacteria were also observed in the small intestine. Conclusions: Guar gum has a trophic effect in the small bo wel, probably related to viscosity, in addition to its fermentation-re lated actions in the colon. Positive interaction with lipid may be ass ociated with delayed absorption. Lipid also has its own direct actions on small bowel mucosal proliferation, which are attenuated by the pre sence of bacteria.