The AAP issued new guidelines several months ago that advise parents to not give up on giving their lactose-intolerant children dairy products. The reason: The calcium in these foods is important for bone mineral health, and dairy products also contain other nutrients important for growth in children and teens.

Lactose intolerance is often mild enough so that kids can tolerate at least some milk and milk products, experts added.

"Lactose intolerance is relatively common," noted Dr. Melvin Heyman, a professor of pediatrics at the University of California, San Francisco, and a member of the committee that wrote the AAP guidelines.

While he was not familiar with any study citing the exact prevalence, he estimated that 20 percent or 30 percent of U.S. children have "some degree of lactose intolerance."

However, "there is a lot of confusion," Heyman said. Parents often confuse milk protein intolerance and lactose intolerance, he said. "Some people do get allergic to the protein in milk," he added. That condition can be serious but probably affects only three to five percent of children in the U.S., he said.

An intolerance for lactose -- the sugar found in milk -- is much more common. Even with this sensitivity, Heyman said, the new thinking is that children may still tolerate some dairy.

To be sure calcium intake is sufficient, Heyman sometimes tells parents to focus more on yogurt and cheese than on milk, especially if milk gives their child the classic intolerance symptom of abdominal pain. "There is less lactose in yogurt and cheese compared to milk," he explained.

Or, your child may be able to drink a little milk without the reaction of stomach pain, he said.

Parents can also educate themselves about lactose intolerance, added Dr. Frank Greer, a professor of pediatrics at the University of Wisconsin, Madison, and chairman of the Academy's Committee on Nutrition.

"If you child is going to have a lactose-intolerance problem, it's usually identified as a problem in the first five years," Greer said. Certain ethnic and racial groups are more likely to suffer from the condition, including blacks, Hispanics and some Asians, he added.

Even if there is a problem, Greer said, "the position now is that your child, even if lactose intolerant, can really tolerate small amounts of lactose, especially in dairy products other than milk, such as yogurt and cheese. Even with milk, you can sort of build up a tolerance."

Moderation may be key, Heyman said. Your child may be able to have one glass of milk, but probably not two or three in a day.

If you suspect your child has lactose intolerance, Heyman said, your pediatrician will probably suggest taking him or her off all dairy for two weeks. "If the symptoms go away, we can be pretty sure it's lactose intolerance," he said.

If it's still not clear, there is a simple in-office test your doctor can do, Heyman noted.

When choosing dairy products for your child, look at the label to be sure you are getting a healthy dose of calcium. "Ideal would be the same amount as in milk, 250 or 300 milligrams [per serving]," he said.

More information

There's more on lactose intolerance at the U.S. National Institute of Diabetes and Digestive and Kidney Diseases.