Lactose

Nutrient, sweetener: Whipped topping mix, fortified breakfast pastry.
Lactose, a carbohydrate that is found only in milk, is nature's way of delivering calories to infant mammals. One-sixth as sweet as sugar, it is used as a slightly sweet source of carbohydrate. The intestine secretes an enzyme that splits lactose into its two principal sugars: glucose and galactose. Children suffering from galactosemia, a rare genetic disease, can suffer serious harm by consuming lactose. Far more common is ‘lactose intolerance', where undigested lactose is metabolized by bacteria, producing gas, bloating, and flatulence. Most Asians and people of black African heritage cannot tolerate as much lactose as Caucasians after early childhood. Some people are acutely lactose intolerant, but most people with lactose intolerance can safety eat smaller amounts of dairy products or foods with added lactose.