Lactulose is a synthetic disaccharide (a special kind of sugar). It can be obtained from Lactose, at high temperatures. When milk is treated using heat, for example with pasteurization, some Lactulose will be result as well. Friedrich Petuely (1922-94) discovered that Lactulose also has properties that are useful for medical treatments: It is beneficial to the gut flora of infants. In larger quantities, in adults, it acts as a laxative. In the gut, Lactrulose favors the growth of bacteria that can process lactose.