lactulose A disaccharide of galactose and fructose which does not occur naturally but is formed in heated or stored milk by isomerization of lactose. About half as sweet as sucrose. Not hydrolysed by human digestive enzymes but fermented by intestinal bacteria to form lactic and pyruvic acids. Thought to promote the growth of Lactobacillus bifidus and so added to some infant formulae; in large amounts it is a laxative. See also lactitol.

lactulose (lak-tew-lohz) n. a disaccharide sugar that acts as an osmotic laxative. Administered by mouth, it remains intact until it reaches the colon. There it is split by bacteria into simpler sugars that help to retain water, thereby softening the stools. Trade names: Lactugal, Regulose.