What is lactose intolerance?
Lactose intolerance is a condition caused by a lack of an enzyme called lactase, which, in turn, causes the body to be unable to digest lactose, a sugar found in milk and milk products.
Lactase is normally produced by cells lining 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.
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-American, Jewish, Mexican-American, and Native American adults are lactose intolerant.
Ninety percent of Asian-American adults are lactose intolerant.
Lactose intolerance is least common among people with a northern European heritage.
What causes lactose intolerance?
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 adults.
What are the symptoms of lactose intolerance?
The following are the most common symptoms of lactose intolerance. However, each individual may experience symptoms differently. Symptoms begin to appear in Caucasian children after age five, and in African-American children by two years of age.
Common symptoms, which begin about 30 minutes to two hours after consuming foods or beverages containing lactose, may include:
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 medical conditions or problems. Always consult your doctor for a diagnosis.
How is lactose intolerance diagnosed?
The most common diagnostic tests used to measure the absorption of lactose in the digestive system include the following:
Lactose tolerance test. This test measures the absorption of lactose in the digestive system. Beginning with fasting before the test and then drinking a liquid that contains lactose, several blood samples are taken over a two-hour period to measure the person's blood glucose (blood sugar) level. The blood glucose test indicates how well the body is able to digest lactose.
Hydrogen breath test. The patient drinks a lactose-heavy beverage, and the breath is 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.
Stool acidity test. This test, used in infants and young children, measures the amount of acid in the stool. Lactic acid and glucose, produced by undigested lactose, and other fatty acids can be detected in a stool sample.
Treatment for lactose intolerance
Specific treatment for lactose intolerance will be determined by your doctor based on:
Your age, overall health, and medical history
Extent of the condition
Your tolerance for specific medications, procedures, or therapies
Expectations for the course of the condition
Your opinion or preference
Although there is not a treatment to improve the body's ability to produce lactase, symptoms caused by lactose intolerance can be controlled with a proper diet. In addition, lactase enzymes may be suggested by your doctor.
Young children with lactase deficiency should be under the care of a doctor.
In September of 2006, the American Academy of Pediatrics released new guidelines for treating lactose intolerance. These guidelines support the use of dairy foods as an important source of calcium for bone growth and maintenance, as well as of other nutrients needed for growth in children and adolescents.
In the past, it had been recommended that dairy products should be eliminated from the diet to treat lactose intolerance. The new guidelines suggest that dairy foods should be tried to see which ones can be tolerated better than others. While the symptoms of lactose intolerance can be unpleasant, the condition does not damage the body. Thus, dairy foods that cause less disagreeable symptoms should be used in the diet to ensure adequate intake of calcium and other important nutrients.
Calcium for people with lactose intolerance
Calcium is essential for the growth and repair of bones throughout life, and has been suggested as a preventive for other diseases. Because milk and other dairy products are a major source of calcium, lactose intolerant children and adults must be concerned with getting enough calcium in a diet that includes little or no milk.
The recommended daily dietary allowance (RDA) for calcium, released in 2010 by the National Academy of Sciences, varies by age group:
0 to 6 months, 200 mg
7 months to 1 year, 260 mg
1 to 3 years, 700 mg
4 to 8 years, 1,000 mg
9 to 18 years, 1,300 mg
19 to 50 years, 1,000 mg
51 to 70 years, 1,000 mg for men and 1,200 mg for women
Pregnant and nursing women under age 19, 1,300 mg
Pregnant and nursing women ages 19 to 50 years, 1,000 mg
Many nondairy foods are high in calcium, including the following:
Green vegetables, such as collard greens, turnip greens, broccoli, and kale (Swiss chard, spinach, and rhubarb are not listed because the body cannot use their calcium content--they contain substances called oxalates, which block calcium absorption)
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, as evidence shows that the bacterial cultures used in making yogurt produce some of the lactase enzyme required for proper digestion)
Vitamin D is necessary for the body to absorb calcium; therefore, a diet should provide an adequate supply of vitamin D. Sources of vitamin D include eggs and liver, as well as sunlight.