What percentage of children is actually clinically lactose intolerant?
A. The easy answer is very few, no matter what the genetic or ethnic background of the child. In fact, up to age 5 to 7, no child in the United States is lactose intolerant unless he has an intestinal infection or another injury to the lining of the small intestine. That is called secondary lactose intolerance, and it generally heals within six weeks of the infection. What we call adult type lactose intolerance is genetically and ethnically determined. In populations derived from Northern European countries, around one quarter of the population is lactose intolerant, after age 5 to 7. In Asian children, lactose intolerance may appear earlier, and can be found in about 90 percent of adults. Q. How is lactose intolerance diagnosed? >A. The most reliable test for lactose intolerance is the lactose breath hydrogen test. In this test, the person fasts over night, and then comes to the testing lab where he has a breath hydrogen sample obtained by blowing into a bag (or similar container). Th
