Lactose Intolerance Symptoms & Causes

What is lactase?

Lactase is an enzyme that is normally produced in the small intestine, where it breaks down lactose into a form that can be absorbed by the blood. A lack of lactase can cause uncomfortable symptoms for some people; those who exhibit symptoms are said to be "lactose intolerant."

How common is lactose intolerance?

30 to 50 million Americans are lactose intolerant.

Is this disorder more common among certain ethnic groups?

  • 80 percent of all African-Americans and Native Americans are lactose intolerant.
  • Over 90 percent of Asian-Americans are lactose intolerant.
  • Lactose intolerance is least common among Americans with a Northern European heritage.

What causes lactose intolerance?

In young children, lactose intolerance is usually caused by digestive diseases or injuries to the small intestine. But most cases of lactose intolerance develop over a period of many years in adolescents and adults.

What are the symptoms of lactose intolerance?

Each individual may experience symptoms differently, but common symptoms—which typically begin about 30 minutes to two hours after consuming food or beverages containing lactose—include:

Severity varies depending on the amount of lactose consumed and the amount your child can tolerate.