Roughly three-quarters of the world’s adult population has trouble digesting lactose, which is a type of sugar found in milk and other dairy products. For many of these folks, a glass of milk or a slice of pizza triggers gas, bloating, cramps, stomach pain, and diarrhea.
Doctors routinely label people who experience these symptoms as “lactose intolerant” and counsel them to avoid dairy products. “That’s bad advice,” says Dennis Savaiano, a professor of nutrition policy at Purdue University.
Savaiano has been studying lactose intolerance since the 1980s. He says nearly all infants are born with a digestive enzyme called lactase, which allows their gut to break down the lactose in dairy without difficulty. And roughly a quarter of adults — in particular, those of Northern European ancestry — retain high levels of this digestive enzyme. These people have no issues with dairy.
But sometime around the age of five or six, a large number of people experience a gradual drop in their gut’s production of lactase. This drop puts these “maldigesters” at risk for symptoms of lactose intolerance, Savaiano says.
While the conventional advice is to avoid milk and other dairy products, this avoidance tends to augment the problem. Bacteria in the gut that feed on lactose proliferate when regularly exposed to it, he says, and their proliferation helps the human digestive system handle lactose. As a result, “people who regularly drink milk” — including maldigesters — “are less likely to have symptoms because their microbiome becomes adapted to eating dairy,” he explains. On the other hand, avoiding dairy diminishes the gut’s population of these helpful lactose-gobbling bacteria, and this “exacerbates the intolerance,” he says.
“If lactose maldigesters continue to consume lactose regularly, many can become tolerant.”
Lactose maldigesters may never be able to handle a large glass of milk, especially if it’s swallowed on an empty stomach. But a majority of them should be…