The National Institutes of Health convened a panel of experts to reach a consensus on what is known about lactose intolerance. Their consensus, released Wednesday: There is no consensus. It is a real condition, but there are no good numbers for its incidence, little is known about its effects on health, and even less is known about potential treatments.
Lactose is the primary sugar in all mammalian milk, including human milk. Virtually all babies are born with enzymes, called lactases, in their intestines that digest lactose, turning it into a form that can be used by the body. But beginning about the age of 5 or 6, many children, particularly those of African and Asian ancestry, begin to lose the ability to digest the sugar. If they continue drinking milk and eating dairy products afterward, bacteria in the gut often ferment the sugar, producing diarrhea, abdominal pain, flatulence and bloating.
Surprisingly, there are no good estimates of how many people have the problem, and the panel didn't even try to make one. "A lot of people who think they have lactose intolerance don't," Dr. Frederick J. Suchy of the Mount Sinai School of Medicine, chair of the panel, said in a telephone news conference. At the opposite extreme, many people who do not digest lactose properly do not manifest symptoms of lactose intolerance because their gut bacteria do not ferment it. Many people who think they have lactose intolerance, he added, actually have irritable bowel syndrome, inflammatory bowel disease, or perhaps celiac disease.
The disorder can be diagnosed by questioning and careful physical examination, he said. One key is to tell a patient to avoid milk products for a few days and see if the symptoms go away. If lactose intolerance is diagnosed, the physician can then try strategies to see if the patient can tolerate milk. "Small amounts of milk spread throughout the day or taken with meals often can be better tolerated," he said. "Yogurt and hard cheeses may also be better tolerated because they are lower in lactose." Lactase-treated milk is also a good alternative, albeit an expensive one.
Most people who think they are lactose intolerant simply avoid dairy products. Physicians would like adults to consume reasonable quantities of such products because of the crucial nutrients they contain, particularly vitamin D and calcium. Those can often be found in fortified products, such as orange juice, but at a higher cost. "We know that, particularly in children and adolescents, it is very difficult to receive adequate calcium and vitamin D if you avoid dairy products completely," Suchy said. "Many parents perceive themselves as lactose intolerant and impose that on the child without any testing." Nonetheless, there are almost no data available to suggest what the health effects of avoiding dairy products might be.
The current research on lactose intolerance "is small and haphazard ... and there are huge gaps in knowledge," Suchy concluded. "We need to define prevalence, develop gold standards for diagnosis, and test management approaches."
-- Thomas H. Maugh II
Dairy products are the best source of vitamin D and calcium for youngsters. Credit: Jessica Tefft / Associated Press