Lactose intolerance

Alternative names:

dairy product intolerance; disaccharidase deficiency; lactase deficiency; milk intolerance

Definition:

An intolerance to milk and some dairy products caused by an inability to digest lactose (milk sugar).

Causes, incidence, and risk factors:

Lactose is a substance found in milk and milk products. Inadequate production of the enzyme lactase in the small intestine results in the body's inability to digest lactose. Patients with lactose intolerance who have ingested milk products may have symptoms such as abdominal bloating, excessive intestinal gas, nausea, diarrhea, and abdominal cramping.

Lactose intolerance is very common in adults and is not dangerous. Most adults, by the time they are 20 years old (approximately 30 million Americans), have some degree of lactose intolerance. This may be present at birth, develop in infancy when cow's milk is introduced in the diet, or develop later in adulthood.

Lactose intolerance can be a serious condition in infants and small children because milk is the basis of the child's diet. Eliminating milk from the diet can result in a deficiency of calcium, vitamin D, riboflavin, and protein. A milk substitute is a necessity. Commonly available soy formulas are adequate substitutes. Soy formulas need not be limited to infants. Toddlers to teens can drink soy formula if needed. Older children may also use lactase treated milk or find alternate dairy sources, such as cheese or yogurt.

A lactase deficiency may affect as many as 70 to 90% of Asian, African, Native American, and Mediterranean populations. In northern and western Europeans, the incidence is 10 to 15%. Lactase deficiency may also occur as a result of intestinal diseases such as celiac sprue and gastroenteritis, or it may follow gastroduodenal surgery. Temporary lactase deficiency can result from viral and bacterial enteritis, especially in children, when the mucosal cells of the intestine are injured. Risk factors are being: Asian, Black, Native American, Mediterranean, previous gastroduodenal surgery, recent intestinal infection, history of intestinal diseases. Overall incidence is 6 out of 10,000 people.