Overview, Causes, & Risk Factors
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.
congenital
acquired
temporary
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 birth.
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 gas.
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
candy
cereals
instant soups and drinks
lunch meat
margarine and salad dressings
Lactose may also be found in both over-the-counter and prescription medicines. Common examples include antacids and oral contraceptives.
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 birth.
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 gas.
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:
Lactose may also be found in both over-the-counter and prescription medicines. Common examples include antacids and oral contraceptives.
Symptoms & Signs
What are the signs and symptoms of the condition?
Common symptoms of lactose intolerance include:Infants with congenital lactase deficiency may have some of the following symptoms:
Diagnosis & Tests
How is the condition diagnosed?
Diagnosis of lactose intolerance begins with a medical history and physical exam. The healthcare provider may order the following tests:In most cases, such tests are not required. If lactose intolerance is suspected, then milk and milk products can be eliminated from the diet for a period of time. If the symptoms go away, then lactose-containing foods should be added back into the diet to be sure that lactose was the culprit.
Prevention & Expectations
What can be done to prevent the condition?
There is no prevention for lactose intolerance. Individuals may reduce their symptoms by avoiding foods high in lactose. Lactose may be better tolerated if it is eaten with other foods.What are the long-term effects of the condition?
In most cases, there are no long-term effects from lactose intolerance. However, an infant with congenital lactase deficiency can become very dehydrated and fail to thrive.What are the risks to others?
Lactose intolerance is not contagious and poses no risk to others.Treatment & Monitoring
What are the treatments for the condition?
Infants and young children with lactose intolerance should not eat or drink foods containing lactose. This includes milk and milk products. Special infant formulas are available for babies with congenital lactose intolerance. Older children and adults may be able to eat or drink limited amounts of lactose-containing foods.The enzyme lactase is available in tablet or capsule form. Persons with lactose intolerance can sometimes tolerate milk products if they take a lactase tablet first. Liquid lactase may also be added to milk to lower the lactose content before the person drinks it. Dietary counseling can be helpful to an individual with lactose intolerance. The dietary plan should include foods high in calcium and vitamin D.
What are the side effects of the treatments?
Lactase supplements have no significant side effects.What happens after treatment for the condition?
If the ability to digest lactose has been permanently lost, treatment might be lifelong.How is the condition monitored?
Any new or worsening symptoms should be reported to the healthcare provider.Attribution
Author:John Wegmann, MD
Date Written:
Editor:Crist, Gayle P., MS, BA
Edit Date:08/28/01
Reviewer:Eileen McLaughlin, RN, BSN
Date Reviewed:08/27/01
Date Written:
Editor:Crist, Gayle P., MS, BA
Edit Date:08/28/01
Reviewer:Eileen McLaughlin, RN, BSN
Date Reviewed:08/27/01
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