Prebiotics are food for commensals
Prebiotics are fermentable complex carbohydrates and dietary fibers. Prebiotics are not digested in the small intestine, but reach the colon intact, where they ‘feed’ the microbiota. Examples of prebiotics are: fructooligosaccharides (FOS), galactooligosaccharides (GOS), acacia fiber, resistant dextrin, and inulin. They play an important role in both gut health and overall health. Prebiotic dietary fibers are components of fruit & vegetables, whole grains, potatoes, seeds, nuts and legumes.
Probiotics deliver food for commensals
The role of probiotics as food for commensals is indirect. The probiotic bacteria themselves are not the food, but the metabolites they produce are food for the commensals. This phenomenon is called cross-feeding and is explained in detail here .