Chitosan is a new dietary fiber derived from chitin, a polysaccharide, derived from the shells of crustaceans. Chitosan does not contain any appreciable amounts of toxic minerals such as mercury, which have previously been associated with the meaty portions of certain shellfish.

Like other fibers, Chitosan is indigestible, and can reduce "transit time", which is the time it takes for foods to pass through the digestive system and out of the body. Therefore less fats in general, including cholesterol, sterols, fatty acids, and essential fatty acids are available to be absorbed. Dietary fiber is usually deficient in modern diets where foods are more highly processed. Fiber tends to increase stool bulk, hydration and it acts as a catalyst for colonic microflora, all of which speed transit time, and produces a softer stool.