Fructooligosaccharides (FOS) are natural sugars that are used as food by healthful bacteria in the gut. The body cannot digest FOS; instead, they are utilized in the gastrointestinal tract by active beneficial bacteria, known as probiotics, such as acidophilus and bifidus. These bacteria aid in digestion and help to maintain a balanced gastrointestinal ecosystem. Most of the health benefits of FOS are related to their ability to stimulate acidophilus and bifidus bacterial growth. In addition, FOS is sometimes used in place of sucrose as a food sweetener.
Good sources of FOS are onions, garlic, asparagus, Jerusalem artichoke, various fruits, and herbs such as chicory.
There is no RDI for fructooligosaccharides. There are no known side effects from large intakes of FOS.