University of Iowa Health Science Relations and
Joel Weinstock, MD
Professor of Internal Medicine
Peer Review Status: Internally Peer Reviewed
Cereal with milk, cottage cheese, creamy sauces, and ice
cream--the milk products that are routine mealtime items for many
people may cause gastrointestinal problems for others who have
developed lactose intolerance. This condition results from a lack of
an enzyme, lactase, in the intestines, says Dr. Joel Weinstock,
professor of internal medicine at the University of Iowa College of
The lactase enzyme is necessary for digesting the sugar lactose
that is found in milk and dairy products, explains Weinstock, who
also is Director of the Division of Gastroenterology-Hepatology and
Center for Digestive Diseases and a staff physician at UI Hospitals.
"Most everyone is born with an adequate supply of the enzyme, but as
people grow older, some lose part of the enzyme," he says. Scientists
do not know why some people lose the enzyme and why others don't.
The symptoms of the condition depend upon the severity of the
intolerance. Most people who cannot tolerate lactose feel bloated and
pass lots of gas when they consume too many milk products, and some
may develop diarrhea, Weinstock says. The symptoms generally
disappear when milk products are reduced or eliminated from the diet.
Lactose intolerance is not serious and does not lead to other medical
problems, he notes.
The tendency for this intolerance usually is inherited and certain
racial groups, such as Asians, Arabs, Jews, and blacks are more
likely to develop the condition, he says. Lactose intolerance is very
common in older adults and rare in children.
To diagnose the condition, a physician may give a patient a
lactose tolerance test or simply remove milk products from the diet
to see the consequence. Once it has been determined that a patient is
lactose intolerant, there are several ways to deal with the
condition. Those with a moderate case may feel better by simply
reducing the amount of milk products in their diets. In more severe
cases, milk products may need to be cut out of the diet entirely,
Fortunately there are milk substitutes on the market that can
replace the real thing. Those with lactose intolerance who are still
milk lovers can drink milk if they first treat it with an enzyme.
Once mixed into the milk, the enzyme breaks down the lactose, making
it safe for use, Weinstock explains. The enzyme is available at many
There are many foods other than the above-mentioned milk products
that may contain lactose. They include coffee creamers, breads, and
prepackaged foods, he says. Cheese and yogurt are usually better
tolerated than other milk products. The cultures in yogurt contain
the enzyme lactase, which aids the digestion of lactose. Also, skim
milk contains a slightly higher concentration of lactose than whole
milk and should be avoided, he adds.
If plagued by gastrointestinal problems or discomfort, see your
physician to determine if you have lactose intolerance or other
conditions that cause similar symptoms, Weinstock says.