Thus, consumption of prebiotics may facilitate the health of the host. Based on the previous classifications, plant-derived carbohydrate compounds called oligosaccharides are the main source of prebiotics that have been identified. Specifically, fructans and galactans are two oligosaccharide sources which have been found to stimulate the activity and growth of beneficial bacterial colonies in the gut. Fructans are a category of carbohydrate consisting of fructooligosaccharides (FOS) and inulins, while galactans consist of galactooligosaccharides. Other dietary fibers also fit the definition of prebiotics, such as resistant starch, pectin, beta-glucans, and xylooligosaccharides.