Lactose is a sugar in dairy products such as cheese and milk. Lactase, an enzyme in the intestines, digests lactose. Without enough lactase, lactose intolerance can occur.
Lactose intolerance is common. It affects almost 50 million Americans. Almost half of all babies with persistent diarrhea have it. Anyone can have it, but it’s more common in African Americans, Asians, and Mexican Americans.
Cells that make lactase enzyme can be damaged by injury or diseases, and then don’t make enough lactase. Rarely, children are born with a lactase enzyme deficiency and cannot make lactase.
Most symptoms occur within 30 minutes to 2 hours after eating milk products. They include stomach pain and cramps, bloating, nausea, diarrhea, gas, feeling sick, and rumbling sounds in the abdomen (belly). Children have slightly different symptoms: foamy diarrhea, diaper rash, slowed growth and development, and sometimes vomiting.
The health care provider will take a medical history and do a physical examination. Tests are done to measure absorption of lactose in the digestive tract. These tests are the lactose tolerance test, hydrogen lactose breath test (most accurate test), and stool acidity test (for children). Rarely, a small tissue sample (biopsy) may need to be taken from the intestine for study when the diagnosis is unclear.
Babies and young children shouldn’t have foods containing lactose. Older children and adults usually don’t have to avoid lactose completely but should figure out the amount that they can have, based on symptoms after ingestion of lactose. Calcium and vitamin D pills may be needed to replace what would normally be obtained from milk. Calcium is very important for children, teenagers, and pregnant, breastfeeding, and postmenopausal women. Instead of calcium pills, eating more calcium-rich foods, such as shrimp, broccoli, and leafy green vegetables, is possible. Over-the-counter lactase enzymes (drops or chewable) are available. Drops can be put into milk. Chewable tablets help people digest solid foods.
Symptoms take about 3 weeks to go away once eating dairy products stops.
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