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Lactose Intolerance

What Is Lactose Intolerance?

Lactose intolerance is an impaired ability to digest lactose, a type of sugar found in milk and other dairy products. During digestion, lactose is broken down into two simple sugars by lactase, an enzyme found in the small intestine. However, if an insufficient amount of this enzyme is produced, lactose cannot be properly digested, resulting in abdominal discomfort within 30 minutes to two hours after consuming milk or milk-based foods.

The degree of lactose intolerance varies from person to person. In most cases, the ability to digest lactose was present at birth but was lost, either suddenly or gradually, between the ages of three and 20. The condition is very common; indeed, it is estimated that over 70 percent of the world’s adult population cannot digest lactose, with the exception of people of northern European descent, of whom less than 20 percent are lactose-intolerant. Most African American, Asian, and Native American adults produce little or no lactase. Lactose intolerance is not a health risk, and symptoms may be controlled by following dietary measures.

Who Gets Lactose Intolerance?

Many Americans who believe they are lactose intolerant are mistaken: The prevalence of lactose intolerance is overestimated, according to a review in the Journal of the American Dietetic Association. But the extent of the problem varies widely among different racial and ethnic groups. Only 15 percent of white Americans are affected by some degree of lactose intolerance; the proportion of African Americans affected is significantly higher at 60 to 80 percent. The problem occurs with varying severity in about 90 percent of Asian Americans, 65 to 100 percent of Native Americans, and about 50 percent of Mexican Americans. Up to 75 percent of adults worldwide may be affected.


  • Abdominal pain, cramps, and bloating.

  • Excessive gas.

  • Diarrhea.

  • Audible bowel noises.

  • Weight loss or slow growth in infants and young children.

Causes/Risk Factors

  • Hereditary factors play a role in lactose intolerance.
  • Some chronic gastrointestinal disorders, such as Crohn’s disease may cause lactose intolerance.
  • In infants, an intestinal infection such as gastroenteritis may cause temporary lactose intolerance.
  • Temporary lactose intolerance may result from medication (such as antibiotics or NSAIDs like ibuprofen) that affect the intestinal lining and stop lactase production for a few weeks.

What If You Do Nothing?

Lactose intolerance is not a health risk. But if you are truly lactose intolerant, symptoms can occur whenever you consume milk and other dairy products high in lactose. (However, the amount that you consume makes a difference in how much discomfort you experience.)


  • Lactose intolerance is suspected when stomach upset occurs shortly after consuming milk or other dairy products.

  • Ability to absorb lactose can be determined by administering lactose orally and measuring the resulting rise in blood glucose (lactose tolerance test), or by measuring the amount of hydrogen subsequently exhaled in the breath (hydrogen breath test).

  • If the lactose tolerance test results indicate the presence of a severe lactase deficiency, there may be a variety of culprits, including inflammatory bowel disease and malabsorption syndromes. Additional testing will usually be done to identify the precise cause.

  • To measure lactic acid in the stool for infants and small children, a stool acidity test may be performed.

  • Many times, the diagnosis rests on a patient’s description of symptoms and response to elimination of lactose in the diet, and does not always require another test.


  • Eliminate or reduce the amount of dairy products in your diet, including milk, cream, cheese, butter, and ice cream.
  • Experiment: You may be able to tolerate moderate amounts of milk. Many people have a certain low level of lactose that they tolerate and that will not cause symptoms. Sometimes lactose is better tolerated when consumed with a meal. Lactose-reduced milk and ice cream are available.
  • Add lactase drops to milk or swallow lactase tablets or caplets just prior to meals. The lactase in these over-the-counter supplements will break down most lactose in dairy products.
  • Try yogurt with live cultures. Yogurt contains less lactose than milk, and the bacteria predigest much of what remains. Look for live or active cultures listed on the label.
  • Substitute soy milk (a liquid made from soybeans) for cow’s milk. Soy milk may be fed to babies, poured on cereal, and used in baking. Other types of lactose-free foods include almond and coconut milk products.
  • Make sure to get enough calcium and Vitamin D in your diet. Broccoli, calcium-fortified orange juice, amaranth (a grain), and legumes are good choices. Your doctor may advise calcium and/or Vitamin D supplements as well.
  • Be aware that lactose is commonly found in many foods, including baked goods such as breads, cookies, and cakes; pancake mixes; some powdered drinks such as cocoa and flavored coffees; processed meats such as frankfurters; and some canned and powdered soups.
  • Hard, aged cheeses, like cheddar and Parmesan, are very low in lactose.
  • Many medications contain lactose as an additive—check with your pharmacist.


There is no known way to prevent the development of lactose intolerance (although treatment can prevent symptoms).

When To Call Your Doctor

See your doctor if self-treatment for lactose intolerance does not relieve abdominal discomfort.

Reviewed by Jenifer K. Lehrer, M.D., Department of Gastroenterology, Aria-Torresdale Hospital, Aria Health System, Philadelphia, PA. Review provided by VeriMed Healthcare Network.