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Lactose intolerance: Too Little Is Known

Panel Says More Research Needed, Not Less Dairy
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WebMD Health News
Reviewed by Louise Chang, MD

Feb. 24, 2010 -- People who are lactose intolerant often avoid dairy products, thereby depriving themselves of calcium, vitamin D, and other essential nutrients, according to a draft statement released today by a National Institutes of Health-sponsored panel on lactose intolerance and health.

The panel, composed of experts from across the medical spectrum, was tasked with evaluating what we know about lactose intolerance. Very little, as it turns out.

"There are huge gaps in knowledge," says panel chairman Frederick J. Suchy, MD, professor and chief of pediatric hepatology at Mount Sinai School of Medicine.

Lactose Intolerance Information Lacking

The panel reviewed nearly 60 relevant studies, a quarter of which were conducted in the United States. "None of the studies," the draft states, "evaluated a representative U.S. sample ... [and] they cannot be used to estimate the prevalence of lactose intolerance."

The numbers may be elusive, but outcomes of a dairy-poor diet are easy to predict.

"It has implications for bone health, cardiovascular health, and maybe colon cancer," Suchy says. But for those who experience symptoms of lactose intolerance -- bloating, gas, diarrhea -- after a glass of milk, "the reflex response is to stop drinking milk and eating dairy products."

What Is Lactose?

Lactose is a sugar found in milk. In order to digest it, the body needs a special enzyme, called lactase. Everyone is born with lactase; otherwise, babies and breast milk wouldn’t mix very well. But most of the world’s population -- people of northern European descent are an exception -- is genetically programmed to decrease the production of lactase around age 3 or 4.

In the U.S., Asians, African-Americans, Hispanics, and other minority groups are particularly likely to be deficient of lactase.

However, not everyone who is deficient of lactase will suffer from drinking a glass of milk.

"Whether or not it becomes clinically important is very variable," says John Snyder, MD, chief of gastroenterology, hepatology, and nutrition at Children’s National Medical Center in Washington, D.C. It is quite possible, he says, that someone with a low level of lactase will tolerate dairy products as well as someone whose level is a lot higher.

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