She said she couldn’t eat it because she’s lactose-intolerant. What exactly does that mean?

Q. My co-worker rejected a
vegetable dish that had a sprinkling of mozzarella cheese on it. She said she
couldn’t eat it because she’s lactose-intolerant. What exactly does that
mean?

A. Up to 20% of Americans say they
are lactose-intolerant, at least to some degree. Lactose is a large sugar
molecule that’s in milk and other dairy products. Everyone is born with an
enzyme called lactase that breaks down lactose into smaller
molecules that are more easily absorbed from the small intestine. In some
individuals, though, lactase stops being produced after childhood. That means
they can’t digest lactose—they become lactose-intolerant.

Symptoms of lactose intolerance include diarrhea, gas, abdominal pain and
bloating, and gurgling noises in the stomach. These symptoms are in part due to
lack of the sugar’s absorption and to its later digestion by bacteria in the
colon, a process that produces intestinal irritants.

Avoiding dairy products for a period of time not only reduces symptoms, it
may also reduce the numbers of lactose-digesting colon bacteria. Thus if a
person begins to consume lactose later on, particularly in small amounts, it may
be much better tolerated than it was previously.

Lactose-intolerant individuals have two choices. One is to give up dairy
foods altogether. The other is to try to build up a tolerance by eating small
amounts of dairy food to start and then gradually increasing consumption. Cheese
tends to have the least amount of lactose, while whole milk has the most. It
also helps to eat other foods together with dairy products.