The gastrointestinal tract is populated by a collection of microorganisms, primarily bacteria, that interact with intestinal host cells. In the past two decades, several studies have demonstrated the effects of the intestinal microbiota on host physiological, metabolic and immunological processes and have revealed that the microbiota is fundamental to host body function. There is currently a growing interest in manipulating the intestinal microbiota to enhance the effects on health and welfare of the intestine. In this regard, since its introduction, the concept of prebiotics has stimulated both scientific and industrial interest. A dietary prebiotic is a selectively fermented ingredient that results in specific changes, in the composition and/or activity of the gastrointestinal microbiota, thus conferring benefits upon host health. To date, the prebiotics most widely evaluated in human clinical trials are inulin-type fructans (inulin, fructo-oligosaccharides, oligofructose) and galacto-oligosaccharides (GOS).