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Lactose Intolerance

Lactose Intolerance
Definition
Lactose intolerance occurs when a person cannot digest lactose, a sugar
found in milk and other dairy products. Lactose intolerance develops
when lactase, an enzyme that is needed to break down milk sugar into
simpler sugars, is less available or absent.
Description
Lactose intolerance is a very common chronic digestive disorder in which
a person
breaks down lactose, or milk sugar, into two simpler sugars that the body
can use. A person can have a lactase deficiency without having the symptoms
of lactose intolerance.
Lactose intolerance is not the same as being allergic to cow
An allergy to cow
lactose intolerance has to do with the process of digestion.
Lactose intolerance may be caused by any of three different factors. One
is normal aging. As people get older, their small intestine produces lower
amounts of lactase. After the lactase production drops below a certain point,
the person may experience the symptoms of lactose intolerance.
A second cause of lactose intolerance is diseases of the intestines or
surgical procedures in which part of the small intestine is removed. These
disorders or operations may affect the part of the
small intestine that secretes lactase. The third
cause of lactose intolerance is genetic. A few
people inherit lactose intolerance from both
parents and are affected from birth.
The symptoms of lactose intolerance usually
begin within half an hour to two hours after
drinking milk or eating a meal high in dairy products.
The person typically experiences diarrhea,
which is the most common symptom of lactose
intolerance, along with a gassy, bloated feeling,
abdominal cramps, and possibly nausea. The
severity of the symptoms is not necessarily related
to the amount of milk or dairy products that
were consumed but rather to the person
ethnicity, and the speed of his or her digestive
processes.
s age,


Demographics
In most cases, lactose intolerance is part of the
normal human developmental process. Most
mammals stop producing lactase after they are
weaned because they are eating solid food instead of drinking milk
from the mother. Humans begin to slow down the production of lactase
some time around age three to five years; thus most human adults
are at some risk of developing lactose intolerance.
It is noteworthy, however, that the levels of lactose intolerance
vary quite widely among different ethnic groups. In some groups,
almost 100 percent of the adult population may be lactose intolerant.
In the United States and Canada, lactose intolerance is estimated to
affect between 20 and 60 percent of the adult population. In terms
of specific ethnic groups, people of Dutch, Swedish, German, or
other northern European descent have low rates of lactose intolerance
(about 5 percent); persons of southern European ancestry have rates
between 18 and 25 percent; African Americans have a rate around
45 percent; persons from Japan or southeastern Asia have rates above
95 percent; and Native Americans are almost 100 percent lactose
intolerant.
One theory that has been proposed to explain these differences is the
long-standing differences among human societies in milk consumption
after childhood. In Asia and Africa, children were rarely given milk after
being weaned; in these societies, lactase production generally falls by
90 percent by the time the child is four years old. In societies in which
milk consumption continues into adult life, however, a mutation on
chromosome 2 that bypasses the normal shutdown of lactase production
became widespread in the population. Thus members of these groups
can continue to consume milk and dairy products throughout their adult
lives. Some researchers have traced the mutation back as far as 4500
BCE
in both Sweden and the Middle East.
Causes and Symptoms
Lactose intolerance results from a drop in or disruption of the production
of lactase in the small intestine. Lactase is produced by specialized cells in
the membrane that lines the villi, which are small finger-like projections
on the walls of the small intestine. The production of the enzyme may
drop at a certain age or because a disease or radiation treatment for cancer
has damaged the villi of the small intestine.
The symptoms of lactose intolerance are diarrhea, bloating, nausea,
and a gassy feeling within thirty minutes to two hours following a meal
high in dairy products. They do
digestive tract, or weight loss in adults. People who have these symptoms
should be checked by their doctors for other disorders of the intestines.
not include fever, bleeding from the
Diagnosis
Diagnosis of lactose intolerance is based on a patient
a detailed history of the patient
Many people underestimate the amount of milk or products containing
lactose that they consume; they may not think of yogurt or ice cream, for
example, as milk products. After getting a complete picture of the
patient
for a week or so in order to see whether the symptoms improve. If they
do, further testing may be unnecessary.
There are three tests that can be used, one of which is generally given
only to infants and small children. It is a test that measures the acidity of
the child
and forms an acid that can be measured in the stool sample.
The most common diagnostic test used in adults is the hydrogen
breath test. The patient is asked to drink a liquid containing a high level
of lactose. The doctor then measures the amount of hydrogen in the
breath at certain intervals. Undigested lactose reaches the colon and ferments,
causing hydrogen and other gases to be released, absorbed by the
intestines, and eventually exhaled. Large amounts of exhaled hydrogen
indicate that the patient
that the patient is probably lactose intolerant.
The third type of diagnostic test involves taking a small sample of
tissue from the lining of the small intestine and measuring the amount
of lactase present in the tissue sample. This type of test requires a specialized
laboratory to evaluate the results, however, and is rarely used outside
clinical research.
s body is not digesting lactose completely and
Treatment
There are several treatment options for lactose intolerance:
This change in diet usually requires careful reading of labels on
other foods because many processed foods contain milk or milk
solids (see sidebar). In addition, some drug manufacturers use lactose
as a binding substance to carry the active ingredient in the
medication. The patient may need to check with the doctor or
pharmacist about any prescription medications they may be using
to see if the drugs were formulated with lactose.
Completely eliminating milk and dairy products from the diet.
reintroducing small amounts of them. Some people can tolerate
small amounts of yogurt or milk after avoiding them
completely for a few weeks.
Eliminating dairy products from the diet for a time and then gradually
products and other plant-based substitutes for milk.
Using specially manufactured lactose-free milk products or soy
Lactaid, DairyEase, and Lactogest can be purchased without a
prescription.
People who are concerned about the risk of osteoporosis (brittle bones)
can take calcium supplements to keep their bones strong rather than getting
their calcium from milk. Patients should ask their doctors how much
calcium they should be getting from other sources. Most adults should not
take more than 1,200
Prognosis
Most people recover completely by removing milk products from the
diet or by substituting reduced-lactose or lactose-free dairy products for
those that contain lactose.
Prevention
There is no way to prevent congenital or adult-onset lactose intolerance.
The Future
Lactose intolerance is not a life-threatening condition. Most people can
manage quite well by using milk substitutes, watching the amount of
milk and other dairy products that they consume, or by taking overthe-
counter lactase supplements. There are also a number of cookbooks
with lactose-free recipes or recipes that use milk substitutes.
SEE ALSO
Osteoporosis
Celiac disease; Crohn disease; Irritable bowel syndrome;
For more information
BOOKS
Dobler, Merri Lou.
Dietetic Association, 2003.
Goldberg, Phyllis Z.
Eating Well without Dairy Products
Lactose Intolerance Nutrition Guide. Chicago: AmericanHow to Tolerate Lactose Intolerance: Recipes and a Guide for. Springfield, IL: Charles C. Thomas, 1998.
PERIODICALS
Brody, Jane.
York Times
com/gst/fullpage.html?res=9C03E3D91E3BF935A1575AC0A9669C
8B63&sec=&spon=&pagewanted=all (accessed May 3, 2008).
WEB SITES
International Foundation for Functional Gastrointestinal Disorders (IFFGD).
Lactose Intolerance: Definition, Symptoms and Treatment
PDF format (free download) at http://www.iffgd.org/store/viewproduct/122
(updated September 2007; accessed May 4, 2008).
Mayo Clinic.
com/health/lactose-intolerance/DS00530 (updated February 16, 2008;
accessed May 4, 2008).
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK).
. Available online inLactose Intolerance. Available online at http://www.mayoclinic.
Lactose Intolerance
nih.gov/ddiseases/pubs/lactoseintolerance/lactoseintolerance.pdf (updated
March 2006; accessed May 4, 2008).
TeensHealth.
teen/nutrition/diets/lactose_intolerance.html (updated September 2006;
accessed May 4, 2008).

 WORDS TO KNOW
Chronic: Recurrent or long-term
Congenital: Present from birth.
Lactase: An enzyme that breaks down lactose
into simpler sugars during the process of
digestion.
Lactose: A complex sugar found in milk and other
dairy products. It is sometimes called milk sugar.
Villi (singular, villus): Small finger-like projections
along the walls of the small intestine that
increase the surface area of the intestinal wall.
. Available online in PDF format at http://digestive.niddk.Lactose Intolerance. Available online at http://www.kidshealth.org/
Personal Health: Debate over Milk: Time to Look at Facts.New, September 26, 2000. Available online at http://query.nytimes.
Taking dietary supplements that contain lactase. Products like1,500 milligrams of calcium per day.
s history, particularlys consumption of dairy products.s diet, the doctor will usually suggest cutting out dairy productss stool sample. Undigested lactose ferments inside the intestine
s intestinal tract lacks the ability to make lactase, an enzyme thats milk.s milk concerns a persons immune system, whereas

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