Alternate Names : Lactase Deficiency
Lactose intolerance is a condition in which a person cannot digest enough
lactose, the sugar found in milk and milk products. The individual has a
deficiency of an enzyme known as lactase.
What is going on in the body?
People with lactose intolerance don't have enough lactase to break
down the lactose they eat or drink. They are unable to break the lactose down
into glucose, which is the form of sugar used by body cells. When lactase is
missing from the intestine, the condition is called lactase deficiency. There
are three types of lactase deficiency:
Congenital lactase deficiency is a rare disorder that appears to run in
families. Infants begin to have symptoms of bloating and watery diarrhea
shortly after starting on breast milk or formula feeding.
Acquired lactase deficiency comes on gradually over time. It also seems to run
in families. It affects certain ethnic groups more than others. The enzyme
lactase is present in the baby's intestine from about the middle of pregnancy
onward. The amount of lactase in the intestine begins to drop after weaning. By
5 to 7 years of age, a child's lactase activity is about 10% of what it was at
Temporary lactase deficiency sometimes follows gastroenteritis in children. When the child has diarrhea, his
or her intestines are stripped of the enzyme lactase. The child then has
trouble digesting lactose when he or she drinks milk products.
When lactose is not digested, water is retained in the bowel. This results in
bloating and watery diarrhea. Lactose that passes into the large intestine is
fermented by bacteria. This produces carbon dioxide, hydrogen, and methane.
This in turn leads to bloating, cramping, and flatulence, or passing
What are the causes and risks of the condition?
Having no lactase causes lactose intolerance. In young children,
temporary lactose intolerance may follow a stomach virus. About 75% of African
Americans and Native Americans have lactose disorder. As many as 90% of Asian
Americans are lactose-intolerant.
Milk and milk products are the only natural sources of lactose.
However, dry milk powder, whey, curds, and milk solids are common ingredients
in processed foods. Some foods that often contain lactose include:
baked goods, including bread
baking mixes for pancakes, cookies, and cakes
instant soups and drinks
margarine and salad dressings
Lactose may also be found in both over-the-counter and prescription
medicines. Common examples include antacids and oral contraceptives.