Fructooligosaccharides (FOS) are short chains of fructose molecules that are naturally found in various plants, such as chicory root, onions, and garlic. They are classified as prebiotics, meaning they serve as food for beneficial gut bacteria, promoting a healthy digestive system. FOS are often added to food products and dietary supplements for their health benefits, including improved gut health and enhanced mineral absorption. They are not digested in the small intestine, which allows them to reach the large intestine intact, where they can support the growth of good bacteria.