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Lactose Intolerance


Lactose intolerance is a condition caused by a lack of an enzyme called lactase. Inadequate amounts of lactase cause the body to be unable to digest lactose, a sugar found in milk products. Lactase is normally produced in the small intestine, where it breaks lactose down into a form that can be absorbed by the blood. A lack of lactase can cause uncomfortable symptoms for some people. Those who do exhibit the symptoms are said to be lactose intolerant. At Lurie Children’s, lactose intolerance is treated by the Division of Gastroenterology, Hepatology & Nutrition.

Thirty to 50 million Americans (adults and children) are lactose intolerant. The disorder affects some populations more than others:

  • Seventy-five percent of all African-Americans and Native Americans are lactose intolerant.
  • Ninety percent of Asian-Americans are lactose intolerant.
  • Lactose intolerance is least common among people with a northern European heritage.

Digestive diseases or injuries to the small intestine can reduce the amount of enzymes produced and is the usual cause of lactose intolerance in young children. However, most cases of lactose intolerance develop over a period of many years in adolescents and adults.


The most common symptoms for lactose intolerance are nausea, cramps, bloating, gas and diarrhea. However, each individual may experience symptoms differently. Symptoms commonly begin about 30 minutes to two hours after consuming foods or beverages containing lactose. The severity of symptoms varies depending on the amount of lactose consumed and the amount each individual can tolerate. The symptoms of lactose intolerance may resemble other conditions or medical problems. Always consult your child's physician for a diagnosis.

The most common diagnostic tests are the lactose tolerance test and the hydrogen breath test, both of which can be performed on an outpatient basis at the hospital, clinic or physician's office. These tests measure the absorption of lactose in the digestive system.

Lactose Tolerance Test
This test measures the absorption of lactose in the digestive system. After fasting, the patient drinks a liquid that contains lactose. The diarrheal stools are then tested for lactose for the next 24 hours. Undigested lactose fermented by bacteria in the colon creates lactic acid and other fatty acids, which can be detected in a stool sample, along with glucose as a result of unabsorbed lactose.

Hydrogen Breath Test
The patient drinks a lactose-heavy beverage. The breath is then analyzed at regular intervals to measure the amount of hydrogen. Undigested lactose in the colon is fermented by bacteria, resulting in the production of various gases, including hydrogen. When high levels of hydrogen are present in the breath, improper digestion of lactose is diagnosed.


Although, there is not a treatment to improve the body's ability to produce lactase, symptoms caused by lactose intolerance can often be controlled with a proper diet. In addition, lactase enzymes may be suggested by your child's physician.

Calcium is essential for the growth and repair of bones throughout life and has been suggested as a preventive measure for other diseases. Because milk and other dairy products are a major source of calcium, parents must be concerned with lactose intolerant children and teenagers getting enough calcium in a diet that includes little or no milk.

The recommended daily dietary allowance (RDA) for calcium, released in 1997 by the National Institutes of Medicine, varies by age group.

  • 0 to 6 months, 210 mg
  • 6 months to 1 year, 270 mg
  • 1 to 3 years, 500 mg
  • 4 to 8 years, 800 mg
  • 9 to 18 years, 1,300 mg

Many nondairy foods are high in calcium, including green vegetables (such as broccoli and kale) and fish with soft, edible bones (such as salmon and sardines). Yogurt with active cultures may be a good source of calcium for many people with lactose intolerance - evidence shows that the bacterial cultures used in making yogurt produce some of the lactase enzyme required for proper digestion.

Your child's physician may prescribe a calcium supplement if your child is unable to get enough calcium from his/her diet. Vitamin D is necessary for the body to absorb calcium, therefore, your child's diet should provide an adequate supply of vitamin D. Sources of vitamin D include eggs and liver.

Make an Appointment

If you’d like to request an appointment with one of our specialists from the Division of Gastroenterology, Hepatology & Nutrition, call 1.800.543.7362 (1.800.KIDS DOC®). You can also request an appointment online.