1. Definitions

1.1 Prebiotics

Until recently, prebiotics were considered to be non-digestible food ingredients (soluble fibers) with a beneficial effect on the host's state of health. They act by selectively stimulating the growth and/or metabolic activity of one or a limited number of bacterial constituents of the intestinal microbiota, which can also interact with protein receptors located on the surface of the intestinal epithelium and/or bacteria of the microflora, thus modifying both microbial adhesion and immune properties in the digestive tract. Then the definition evolved: the targets of prebiotics were extended to the ecosystems of other mucous membranes, such as the vagina, mouth and skin. Only oligosaccharides met these criteria