Lactose intolerance symptoms not always present from birth

I returned to the exam room with results of the 12-year-old's strep test. She did not have strep throat and, therefore, felt vindicated. The young lady had assured her mom that morning that there was no need to drag her out to the doctor's office for an unpleasant test that was going to be negative, anyway.

Her mother smiled, realizing that she had lost the bet, but knowing that after five days of illness, she had done what any responsible parent needed to do. Before leaving the office, mom wondered aloud why, in addition to the fever and sore throat, the girl was also getting an upset stomach every time she tried to drink milk.

I explained that some children develop lactose intolerance after being hit by a viral infection. Most of these episodes are transient, and after several days to weeks, kids can ease themselves back into normal dairy consumption without a problem.

Pediatricians also see permanent lactose intolerance, an uncomfortable condition with particular significance for growing kids. Childhood is recognized as a critical time for banking nutrients to ensure future bone health, and milk and other dairy products are readily available, reliable sources of vitamin D and calcium.

Researchers at the American Academy of Pediatrics note that children who are deficient in lactase, an enzyme found in the small intestine, will have difficulty in breaking down the carbohydrate lactose. After drinking milk or eating dairy, these kids can experience gastrointestinal symptoms such as bloating, gas, diarrhea, nausea or abdominal pain.

In an updated 2006 policy statement, AAP nutrition experts divide lactase deficiencies into the most common, the primary lactase deficiency, and its lesser known cousins, the secondary, congenital and developmental deficiencies. Secondary lactase deficiency occurs after injury to the small bowel, as in children who've had a bout of viral stomach flu or gone through a round of chemotherapy.

Infants are rarely born with lactase deficiency, so, true congenital deficiency is considered an extremely unusual and life-threatening medical condition. Developmental deficiency is more common, and is defined as the lactase deficiency seen in premature babies born before 34 weeks gestation.

Primary lactase deficiency develops during childhood and is known to affect 70 percent of the human population, with a frequency that varies based on race and ethnicity. According to data gathered by the AAP, this primary deficiency is found in nearly 100 percent of the Asian and American Indian populations, as well as in 60 to 80 percent of black and Ashkenazi Jewish peoples, and in 50 to 80 percent of Hispanic populations.

When lactose intolerance is suspected, a patient can be tested through the use of an elimination diet. Academy specialists recommend taking the child off all dairy products for two weeks, making sure to also read all nutritional labels in order to avoid other "hidden" lactose-containing foods. If the child becomes symptom-free on the lactose-free diet and these symptoms return when lactose products are reintroduced into the diet, you have the answer.

Hydrogen breath tests can also be used to document lactose malabsorption, and less frequently, gastroenterologists perform intestinal biopsies to reach this definitive diagnosis.

What can parents offer their child after discovering that he is lactose intolerant? The AAP reminds parents that while eliminating dairy will eliminate the lactase-deficient child's symptoms, dairy still is a nutritionally important food. Since the degree of lactase deficiency varies from person to person, many affected children and adults find that they can still tolerate and continue to include small amounts of dairy in their diet.

Interestingly, academy authors note that some lactose-intolerant children can also tolerate plain yogurt better than milk, thanks to the digestive effect of its bacteria on its lactose component. Aged cheeses are also easier to handle due to their lower overall lactose content. Other options for lactose-intolerant children include fortified rice and soy milks; lactose-free and lactose-reduced milks; use of oral lactase-replacement capsules, and finally the addition of calcium and vitamin D supplements as needed to reach recommended levels.

• Dr. Helen Minciotti is a mother of five and a pediatrician with a practice in Schaumburg. She formerly chaired the Department of Pediatrics at Northwest Community Hospital in Arlington Heights.