Even though lactose intolerance is a widespread
problem, it need not pose a serious threat to good health. People
who have trouble digesting lactose can learn, by testing themselves,
which dairy products and other foods they can eat without discomfort
and which ones they should avoid. Many will be able to enjoy milk,
ice cream, and other such products if they take them in small amounts
or eat other kinds of food at the same time. Others can use lactase
liquid or tablets to help digest the lactose. Even older women and
children who must avoid milk and foods made with milk can meet most
of their special dietary needs by eating greens, fish, and other
calcium-rich foods that are free of lactose. A carefully chosen
diet (with calcium supplements if the doctor recommends them) is
the key to reducing symptoms and protecting future health.
Lactose intolerance is the inability to digest significant amounts
of lactose, which is the predominant sugar of milk. Close to 50
million American adults are lactose intolerant. Certain ethnic
and racial populations are more widely affected than others. As
many as 75 percent of all African-American, Jewish, Native American,
and Mexican-American adults, and 90 percent of Asian-American
adults are lactose intolerant. The condition is least common among
people of northern European descent.
What Causes Lactose Intolerance?
Lactose intolerance results from a shortage of the enzyme lactase,
which is normally produced by the cells that line the small intestine.
Lactase breaks down milk sugar into simpler forms that can then
be absorbed into the blood stream. When there is not enough lactase
to digest the amount of lactose consumed, the results, although
not usually dangerous, may be very distressing.
Common symptoms include nausea, cramps, bloating, gas, and diarrhea,
which begin about 30 minutes to two hours after eating or drinking
foods containing lactose. Many people who have never been diagnosed
as lactose intolerant or "lactase deficient" may notice
that milk and other dairy products cause problems that don’t
occur when eating other foods. The severity of symptoms varies
depending on the amount of lactose each individual can tolerate.
Some causes of lactose intolerance are well known. For instance,
certain digestive diseases and injuries to the small intestine
can reduce the amount of enzymes produced. In rare cases, children
are born without the ability to produce lactase. For most people,
though, lactase deficiency is a condition that develops naturally,
over time. After about the age of two years, the body begins to
produce less lactase. The reasons for this are unclear and still
under study. However, symptoms may occur years after childhood
What Diagnostic Tests are Used to Detect Lactose
The most common tests used to measure the absorption of lactose
in the digestive system are the lactose intolerance test, the
hydrogen breath test, and the stool acidity test. A doctor can
tell you where to go for these tests, which are performed on an
outpatient basis at a hospital or clinic. A clinical response
to lactose restriction may also be sufficient, at times, to make
The lactose tolerance test can be given to older children as
well as adults. Before the test, patients fast (do not eat), and
blood is drawn to measure the fasting blood glucose (blood sugar)
level. Patients then drink a large amount of a liquid that contains
50 grams of lactose. Blood samples are taken over a two-hour period
to determine the glucose level, which tells how well the body
is able to digest lactose. When the lactose reaches the digestive
system, the lactase enzyme breaks the lactose down into glucose
and galactose. The liver then changes the galactose into glucose.
If this process occurs normally, the glucose enters the bloodstream
and raises the fasting blood glucose level. If lactose is incompletely
absorbed, the blood glucose level does not rise, and a diagnosis
of lactose intolerance is confirmed.
The hydrogen breath test measures the amount of hydrogen in the
breath. Normally, no hydrogen is detectable in the breath. However,
undigested lactose leads to the formation of various gases including
hydrogen, by bacteria in the colon. The hydrogen is absorbed from
the intestines, carried through the bloodstream to the lungs,
and exhaled. In the test, the patient drinks a lactose-loaded
beverage, and the breath is analyzed at regular intervals. Hydrogen
in the breath means improper digestion of lactose. Certain foods,
medications, and smoking can affect the test’s accuracy
and may need to be avoided before the test.
The lactose tolerance and hydrogen breath tests are not given
to infants and young children who are suspected of having lactose
intolerance. Giving these patients a lactose load may be dangerous
because they are more prone to the dehydration that can result
from the diarrhea caused by the lactose. If a baby or young child
is experiencing symptoms of lactose intolerance, many pediatricians
simply recommend changing from cow’s milk to soy formula
and waiting for a decrease in symptoms.
If necessary, a stool acidity test, which measures the amount
of acid in the stool and presents no risk to young children, may
be given. Undigested lactose fermented by colon bacteria creates
lactic acid and other short-chain fatty acids that can be detected
in a stool sample. In addition, glucose may be present in the
sample as a result of unabsorbable lactose in the colon.
What Treatments are Available to Control Symptoms?
Fortunately, lactose intolerance is relatively easy to treat.
No known way exists to increase the amount of lactase enzyme the
body can make, but symptoms can be controlled through diet.
Small children born with lactase deficiency should not be fed
any foods containing lactose. Most older children and adults need
not avoid lactose completely, but individuals differ in the amounts
of lactose they can handle. For example, one person may suffer
symptoms after drinking a small glass of milk, while another can
drink one glass but not two. Others may be able to manage ice
cream and aged cheeses, such as cheddar and swiss, but not other
dairy products. Dietary control of the problem depends on each
person’s knowing, through trial and error, how much milk
sugar and what forms of it his or her body can handle.
For those who react to very small amounts of lactose or have
trouble limiting their intake of foods that contain lactose, lactase
additives are available from drug stores without a prescription.
One form is a liquid for use with milk. A few drops are added
to a quart of milk, and after 24 hours in the refrigerator, the
lactose content is reduced by 70 percent. The process works faster
if the milk is heated first, and adding a double amount of lactase
liquid produces milk that is 90 percent lactose free. A more recent
development is a lactase tablet that helps people digest solid
foods that contain lactose. One to three tablets are taken just
before a meal or snack.
At a somewhat higher cost, shoppers can buy lactose-reduced milk
at most supermarkets. The milk contains all of the other nutrients
found in regular milk and remains fresh for about the same length
A Nutrition Balancing Act
Milk and other dairy products are a major source of nutrients
in the basic American diet. The most important of these nutrients
is calcium. Calcium is needed for the growth and repair of bones
throughout life, and in the middle and later years, a shortage
of calcium may lead to thin, fragile bones that break easily (a
condition called "osteoporosis"). A concern, then, for
both children and adults with lactose intolerance is how to get
enough calcium in a diet that includes little or no milk.
Although the RDA (recommended daily allowance) for calcium, set
in 1980, is 800 mg per day, many experts in bone disease believe
this is too low. The results of a 1984 conference at the National
Institutes of Health (NIH), suggest that women who have not yet
reached menopause and older women who are taking the hormone estrogen
after menopause should consume about 1,000 mg of calcium daily
(roughly the amount in a quart of milk). Pregnant women and nursing
mothers need about 1,200 mg of calcium per day. Postmenopausal
women not taking estrogen may need as much as 1,500 mg of calcium
per day. The RDA for adult men is 1,000 mg per day and 1,500 mg
per day for men in their later years.
It is important, therefore, in meal planning to make sure that
each day’s diet includes enough calcium, even if the diet
does not contain dairy products. Quite a few foods are high in
calcium and low in lactose. Many green vegetables and fish with
soft, edible bones are excellent examples. To help in planning
a high-calcium/low-lactose diet, the following chart lists some
common foods that are good sources of dietary calcium and shows
how much lactose the foods contain.
Recent research has shown that yogurt may be a very good source
of calcium for many lactose intolerant people, even though it
is fairly high in lactose. There is evidence that the bacterial
cultures used in making yogurt produce the lactase required for
Clearly, many foods can provide the calcium and other nutrients
the body needs, even when intake of milk and dairy products is
limited. Still, factors other than calcium and lactose content
should be kept in mind when planning a diet. Some vegetables that
are high in calcium (Swiss chard, spinach, and rhubarb, for instance)
are not listed in this chart because the body cannot use their
calcium content. They contain substances called oxalates, which
stop the calcium absorption. Remember also that calcium is absorbed
and used only when there is enough vitamin D in the body. A balanced
diet should provide an adequate supply of vitamin D.
Some people with lactose intolerance may think they are not getting
enough calcium and vitamin D in their diet. A doctor is the best
person to decide whether any dietary supplements are needed. Taking
vitamins or minerals of the wrong kind or in the wrong amounts
can be harmful. A dietitian can help in planning meals that will
provide the most nutrients with the least chance of causing discomfort.
Some so-called nondairy products such as powdered coffee creamer
and whipped topping also may include ingredients that are derived
from milk and therefore contain lactose.
Smart shoppers learn to read food labels with care, looking not
only for milk and lactose among the contents but also for words
such as whey, curds, milk by-products, dry milk solids, and non-fat
dry milk powder. If any of these are listed on a label, the item
In addition, lactose is used as the base for more than 20 percent
of prescription drugs and about six percent of over-the-counter
medicines. Many types of birth control pills, for example, contain
lactose, as do some tablets for stomach acid and gas. A pharmacist
can answer questions about the amounts of lactose in various medicines.
Watch for Hidden Lactose
Although milk and foods made from milk are the only noteworthy
natural sources, lactose is often added to prepared foods. It
is important for people with very low tolerance for lactose to
know about the many foods that contain lactose, even in small
amounts. Grocery items that may contain lactose include:
- Bread and other baked goods
- Processed breakfast cereals
- Instant potatoes, soups, and breakfast drinks
- Lunch meats (other than kosher)
- Salad dressings
- Candies and other snacks
- Mixes for pancakes, biscuits, cookies, etc.