Lactose intolerance is the inability to digest a sugar called lactose
that is found in milk and dairy products.
Normally when a person eats something containing lactose, an enzyme in the small
intestine called lactase breaks it down into simpler sugar forms
called glucose and galactose. These simple sugars
are then easily absorbed into the bloodstream and turned into energy — fuel
for our bodies.
People with lactose intolerance do not produce enough of the lactase enzyme to
break down lactose. Instead, undigested lactose sits in the gut and gets broken down
by bacteria, causing gas, bloating, stomach cramps, and diarrhea.
Lactose intolerance is fairly common and seems to affect guys and girls equally.
Little kids are less likely to have it, but many people eventually become lactose
intolerant in adulthood — some while they are still teens. Some health care
providers view lactose intolerance as a normal human condition and therefore don't
really consider it a disease.
Who Gets Lactose Intolerance?
A person may be or may become lactose intolerant for different reasons:
Ethnic background. People of Asian, African, Native American,
and Hispanic backgrounds are more likely to develop lactose intolerance at a young
Other problems with the digestive tract. People who have inflammation
of their upper small intestine, such as celiac disease or Crohn's disease, have a
reduced level of the lactase enzyme.
Medicines. Certain antibiotics can trigger temporary lactose
intolerance by interfering with the intestine's ability to produce the lactase enzyme.
Infection. After a bout of infectious diarrhea, some kids can
develop a temporary lactose intolerance that usually improves after a few days or
Age. As people get older, their bodies usually stop producing
the lactase enzyme, and most people will naturally become lactose intolerant over
What Happens When Someone Has It?
People with lactose intolerance may have a variety of symptoms. It all depends
on how much dairy or how many milk-containing foods the person eats and how little
lactase the body produces.
Usually within 30 minutes to 2 hours after eating, someone with lactose intolerance
will experience nausea, stomach cramps, bloating, gas, and diarrhea. This can be unpleasant,
not to mention embarrassing if you're at school or out with friends.
Because many people may think they're lactose intolerant when they really aren't,
it helps to see a doctor who can diagnose the condition correctly and advise you on
ways to manage it.
How Do Doctors Diagnose It?
If your doctor thinks you might be lactose intolerant, he or she will take your
medical history by asking about any concerns and symptoms you have,
your past health, your family's health, any medications you're taking, any allergies
you may have, and other issues. Your doctor will also do a physical exam.
Doctors can test for lactose intolerance by using the hydrogen breath test. Normally
very little hydrogen gas is detectable in the breath. However, undigested lactose
in the colon ferments (breaks down) and produces various gases, including hydrogen.
If your doctor decides to give you a hydrogen breath test, you'll be asked to blow
into a tube for a beginning sample. You'll then swallow a drink with lactose in it,
wait a while, and breathe into the tube again. You'll be asked to blow into the tube
every half hour for 2 hours in order to measure hydrogen levels in your breath. The
levels should go up over time if you have lactose intolerance.
Doctors also can find out if you're able to digest lactose by testing for the presence
of lactase with an endoscopy. During this procedure, doctors view
the inside of the intestines by inserting a long tube with a light and a tiny camera
on the end into the mouth.
A doctor can then take tissue samples and pictures of the inside of your gut and
look for clues to why you've been having problems with what you're eating. The amount
of lactase enzyme can be measured in one of these tissue samples.
Living With Lactose Intolerance
Lactose usually can be easily managed if you're in tune with your body. Everyone's
different, but most people with lactose intolerance can eat a small amount of dairy.
The trick is to eat dairy products in combination with other foods that don't contain
lactose and not to eat too much dairy at once. It can also help to keep a food diary
to learn which foods your body can or can't tolerate.
Dairy foods are the best source of calcium,
a mineral that's important for bone growth. Because growing teens need about 1,300
milligrams (mg) of calcium each day, experts recommend that even teens who have lactose
intolerance continue to include some dairy in their diet.
Foods like cheese or yogurt may be easier to digest than milk, so try a cup of
yogurt for dessert or add a piece of cheese to your sandwich. Lactose-free milk is
also a great way to get calcium in your diet without the problems that can come with
Taking a lactase enzyme supplement might help too. Taking this before eating foods
that contain dairy will help the body digest the lactose sugar in dairy so you don't
develop the symptoms of lactose intolerance, like pain, cramping, bloating, gas, and
Teens with the most severe symptoms of lactose intolerance might have to avoid
all dairy products. It's extra important that these teens find other good calcium
sources, so talking to a registered dietitian is a good idea. Dietitians are trained
in nutrition and they can help people who are lactose intolerant come up with eating
alternatives and develop a well-balanced diet that provides lots of calcium for developing
Here are some tips for dealing with lactose intolerance:
Choose lactose-reduced or lactose-free milk.
Take a lactase enzyme supplement (such as Lactaid) just before you eat dairy products.
These can be taken in drops or tablets and even added directly to milk.
When you do drink milk or eat lactose-containing foods, eat other non-lactose
foods at the same meal to slow digestion and avoid problems. (For example, if you
are going to have a milkshake, don't drink it by itself. Have something else with
it, like a healthy sandwich.)
Drink juices that are fortified with calcium.
Eat a variety of dairy-free foods that are rich in calcium, such as broccoli,
beans, tofu, or soy milk. Consider hard cheeses such as cheddar, which are lower in
Yogurts that contain active cultures are easier to digest and much less likely
to cause lactose problems.
Learn to read food labels.
Lactose is added to some boxed, canned, frozen, and prepared foods like bread, cereal,
lunchmeats, salad dressings, mixes for cakes and cookies, and coffee creamers. Be
aware of certain words that might mean the food has lactose in it: butter, cheese,
cream, dried milk, milk solids, powdered milk, and whey, for example.