L–M

lactose intolerance The inability to digest lac-
tose, a disaccharide sugar in milk and other dairy
products. Lactose intolerance occurs because of a
deficiency of the enzyme lactase, which is neces-
sary to break down lactose into simpler sugar mol-
ecules. It is the most common form of
CARBOHYDRATE INTOLERANCE, affecting an estimated
50 million Americans. Lactose intolerance may be
congenital (present at birth), occur as a conse-
quence of a disease process that affects the cells
that produce lactase (such as CELIAC DISEASE), or
develop with aging as the number of lactase-pro-
ducing cells naturally declines.
Congenital lactose intolerance becomes appar-
ent when a young child begins drinking cow’s
milk, which is high in lactose. The doctor can usu-
ally confirm the diagnosis with a lactose challenge
test in which the child drinks a solution that con-
tains lactose. Breath samples taken at certain
intervals allow measurement of hydrogen, which
increases when lactose remains undigested in the
gastrointestinal tract.
Switching to a fortified SOY formula nearly
always eliminates symptoms when the child is
young. As the child grows older, trial and error
will tell whether he or she can eat small amounts
of other dairy products such as cheese and ice
cream. Many people who have lactose intolerance
produce enough lactase to digest small amounts of
lactose. Lactase enzymes are available without a
doctor’s prescription; added to milk, they act on
the lactose to split it into its composite sugars.
Within 24 hours the milk will be 70 to 90 percent
lactose-free. This approach allows the child to
benefit from the numerous NUTRIENTSmilk and
dairy products provide. Lactose intolerance gener-
ally does not affect an individual’s overall general
health, as long as the person acquires necessary

nutrients through alternative foods or via supple-

ments.

See also AGING, NUTRITION AND DIETARY CHANGES

THAT OCCUR WITH.

malnutrition A state of multiple nutrient deple-

tion that alters body functions. Infants, the elderly,

and people who have active cancer, ALCOHOLISM,

OBESITY, or chronic health conditions are most sus-

ceptible to malnutrition. Malnutrition may

develop when a person does not eat enough food,

eats a very narrow selection of foods, or eats too

much food. Malnutrition is possible with extended

adherence to fad diets that limit food types and

when the diet primarily contains foods that have

low NUTRIENT DENSITYsuch as “junk” foods. The

most severe presentations of malnutrition are the

polar extremes of STARVATIONand obesity.

In the United States malnutrition resulting

from inadequate food or nutrient consumption

occurs most often in the chronically ill, the very

young, and the very old. Most people who have

significant obesity have some degree of nutrient

imbalance, not only among the energy NUTRIENTS

but also of vitamins, minerals, and other micronu-

trients. People who have alcoholism, serious

chronic health conditions such as HIV/AIDS, or gas-

trointestinal MALABSORPTION disorders including

INFLAMMATORY BOWEL DISEASE(IBD) andCELIAC DIS-

EASEor are also vulnerable to malnutrition.

Symptoms and Diagnostic Path

Early malnutrition can be difficult to detect

though initial indications may include dry SKIN,

pallor, swollen or bleeding gums, PETECHIAE(pin-

point hemorrhages under the skin), MUSCLEweak-

ness and atrophy, and disturbances of sensory

perception (PARESTHESIA) in both inadequate and

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