The bifidogenic effect of inulin and oligofructose is now well established in various studies, not only in adult participants but also in other age groups. This bifidogenic shift in the composition of the colonic microbiota is likely the basis for the impact of these prebiotic compounds on various parameters of colonic function. Mainly from animal and in vitro studies and also from some human trials, there are indications, for instance, that inulin-type fructans may reduce the production of potentially toxic metabolites and may induce important immune-mediated effects. This review discusses how these changes in the composition and activity of the colonic microbiota may affect gut health in healthy people, including in those who may experience some form of gastrointestinal discomfort.