Lactose Intolerance

Latest Innovations. Subspecialty Care. Strength in Patient Follow-Up

Lactose intolerance is a condition caused by a lack of an enzyme called lactase. This deficiency results in an inability to digest lactose, a sugar found in cow's milk and cow's milk-based products. Lactase is normally produced in the small intestine, where it breaks lactose down into a form that can be absorbed by the blood.

Tens of millions of people, of all ages, in the U.S., are lactose intolerant. The disorder affects a high proportion of some populations, including African Americans, Native Americans, and Asian Americans. Lactose intolerance is least common among people with a northern European heritage.

Risk factors/causes

Inherited inability to produce lactase is the primary cause of the condition. This is a genetically programmed decrease in lactase production that most commonly becomes more apparent after childhood and into adulthood. Often, lactose intolerance develops over a period of many years in adults.

Digestive diseases or injuries to the small intestine can also reduce the amount of lactase enzyme produced.

Signs & symptoms

Symptoms of lactose intolerance begin about 30 minutes to two hours after consuming foods or beverages containing lactose. Commonly, these symptoms include:

  • nausea;
  • cramps;
  • bloating;
  • gas;
  • or diarrhea.

The severity of symptoms varies depending on the amount of lactose consumed and the amount the individual can tolerate.


In addition to taking a medical history and performing a physical examination, physicians may request the following diagnostic procedures in order to diagnose ulcers. These are aimed at measuring the absorption of lactose in the digestive system:

  • milk challenge test, in which the patients fasts, then drinks milk, and is monitored for symptoms;
  • breath test;
  • lactose tolerance test, in which the patients fast and then drink a liquid that contains lactose, after which they have their blood monitored over a two-hour period to measure the blood glucose (blood sugar) level, which indicates how well the body is able to digest lactose.

Many people attempt to self-diagnose the conditions by eliminating diary products from the diet. This is difficult to do, however, as it must be very stringently adhered to.


Although there is no a treatment to improve the body's ability to produce lactase, symptoms caused by lactose intolerance can be controlled with a proper diet. Those with lactose intolerance will have to carefully monitor their food to avoid dairy-based ingredients. (As a result, they may also want to take calcium supplements to assure they are getting their recommended daily allowance of calcium.) In addition, you physician may suggest trying lactase-enzyme supplements. Some dairy foods already have these as additives to make the products digestible to lactose intolerant individuals.

Young children with lactase deficiency should be under the care of a physician.