Lactose intolerance is the inability to digest significant amounts of lactose, which is predominantly found in milk. It results from a shortage of the enzyme lactase, which is produced by the cells in the small intestine. When there is not enough lactase to digest the amount of lactose consumed, the results may be very distressing. Symptoms include nausea, cramps, bloating, gas and diarrhea which begin between 30 minutes and 2 hours after eating or drinking foods containing lactose. It is estimated that between 30 and 50 million Americans are lactose-intolerant.