Probiotics are living microorganisms that favorably influence the health of the host by improving the indigenous microflora. Prebiotics are nondigestible food components that increase the growth of these probiotic organisms in the gastrointestinal tract. The prebiotic substances derived from whey or lactose include lactitol, lactulose, lactosucrose and galactooligosaccharides.
These compounds are not digested in the small intestine, passing instead to the colon where they serve as fermentation substrates for probiotic bacteria, including Bifidobacterium and Lactobacillus strains. Many new products have been introduced recently in the United States that combine probiotic bacteria and prebiotic ingredients. This combination is called synbiotics.