What is lactose intolerance?

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About lactose intolerance

Lactase is an enzyme normally produced in the small intestine, where it breaks down lactose (a sugar found in milk products) into a form that can be absorbed by the blood. Some people lack sufficient levels of this enzyme, which can cause uncomfortable gastrointestinal symptoms after eating dairy.

What causes lactose intolerance?

The usual cause of lactose intolerance in young children is digestive diseases or injuries to the small intestine that can reduce the amount of enzymes produced. Sometimes a gastrointestinal virus can cause temporary lactose intolerance that goes away after a few days or few weeks. However, most cases of lactose intolerance develop over a period of many years in adolescents and adults.

How common is lactose intolerance?

An estimated 30 to 50 million Americans (adults and children) are lactose intolerant.

What are the symptoms of lactose intolerance?

Symptoms vary but may include:

Symptoms usually 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 your child can tolerate.

The symptoms of lactose intolerance can resemble other conditions or medical problems, so always consult your child’s physician for a diagnosis.

Who is at risk of developing this condition?

This disorder affects some populations more than others. Approximately 75 percent of all African-Americans and Native Americans and 90 percent of Asian-Americans are lactose intolerant. Lactose intolerance is least common among people with a northern European heritage. Lactose intolerance is extremely rare in children under age 5.

Why is lactose intolerance a concern?

The frequent diarrhea, bloating and abdominal pain associated with lactose intolerance can affect your child’s quality of life. If untreated, chronic lactose intolerance can cause malabsorption.

How is lactose intolerance diagnosed/evaluated?

Testing isn’t always necessary to diagnose and treat lactose intolerance. If the doctor suspects lactose intolerance based on your child’s medical history, he or she may suggest your child try eliminating dairy foods to see if that helps. If your child’s symptoms improve somewhat but it’s still unclear whether lactose intolerance is the issue, then the doctor may recommend testing. Tests could include:

  • Hydrogen breath test – After drinking a lactose-heavy beverage, your child’s breath will be 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. High levels of hydrogen indicate improper digestion of lactose.
  • Biopsy – Using endoscopy, the doctor will remove a sample from the lining of your child’s small intestine so it can be analyzed in the laboratory. Children’s Hospital of Wisconsin is one of the few centers in the country that offers an established, accredited laboratory that can measure enzyme activity in the small intestine. Biopsy is the best way to definitively diagnose lactose intolerance or rule out other potential causes for your child’s symptoms.

What is the treatment for lactose intolerance?

This condition can often be controlled with a proper diet, so the first step is to eliminate dairy from your child’s diet for two weeks to see if that improves the symptoms. If your child is diagnosed with lactase deficiency, enzyme supplementation is also an option. Lactase can be purchased over the counter and can be taken prior to consumption of dairy to prevent the uncomfortable symptoms of lactose intolerance.

Sometimes avoiding dairy doesn’t help. In that case, there may be another cause for your child’s symptoms, such as a high-sugar diet or an imbalance in your child’s gut bacteria. In that case, your child’s doctor may suggest other diet modifications.

What happens after treatment?

If your child feels better after changing his or her diet, then you’ll need to continue following the diet to avoid a relapse of symptoms. However, if the symptoms persist, the doctor may recommend additional testing to rule out another condition.

When should you contact a physician?

If you notice that your child frequently experiences nausea, cramps, bloating, gas and/or diarrhea, talk to your pediatrician.

What is the long-term outlook for lactose intolerance?

This is usually a chronic disorder that requires lifelong diet modifications (other than cases of temporary lactose intolerance that can develop after an acute infection in the gastrointestinal tract). But your child can lead a normal life as long as he or she adheres to the recommended diet.

How do I live with lactose intolerance?

The best way to manage symptoms is to monitor your child’s diet and avoid foods and drinks that cause discomfort. Your child’s doctor may also recommend a supplement that contains lactase enzymes, which can help your child digest dairy.

Because milk and other dairy products are a major source of calcium, it’s important to make sure that your child gets enough calcium through other foods. Broccoli, kale, yogurt, salmon and sardines are all good sources of calcium. Your child's physician may prescribe a calcium supplement if your child is unable to get enough calcium from his or her diet.