June 11, 2012 | Lactose intolerance results from a shortage of the enzyme lactase, which is normally produced by the cells that line the small intestine. Lactase breaks down lactose into simpler forms that can then be absorbed into the blood stream. When there is not enough lactase to digest the amount of lactose consumed, the results may include nausea, cramps, bloating, gas, and diarrhea, which begin about 30 minutes to two hours after eating or drinking foods containing lactose. Lactose intolerance occurs in adults when their lactase production decreases as their diet becomes more varied and less reliant on milk. It can also occur when lactase production decreases after an illness, surgery or an injury to the small intestine. It’s also possible for babies to be born with lactose intolerance. Infants with congenital lactose intolerance are intolerant of the lactose in their mothers’ breast milk and have diarrhea from birth. These babies will need to be fed with formula that is lactose free.