Lactose-free dairy milk is milk with added lactase, an enzyme that is used by mammals to digest lactose in milk. Now, children, remember from dairy science clas

Lactose-free dairy milk is milk with added lactase, an enzyme that is used by mammals to digest lactose in milk. Now, children, remember from dairy science class: lactose is a complex sugar made of two siple sugars, glucose and galactose. Lactase breaks lactose down to its constituent simple sugars so that they can more easily be absorbed by picky mammalian guts. Fun fact: lactose-free milk still has all the sugars that made up its original lactose content (you could even argue it still has all its lactose, if you wanted to be really obstinate). Glucose in particular registers as sweeter than lactose and for this reason many "lactose-free" milks have messages on the packaging informing consumers that they have "no sweetener added". Lactose-free milks also tend to be Ultra Heat Treated, which enhances the sweet taste by means of the Maillard reaction. See wikipedia.