About 80% of the water the average person needs
is replaced by drinking liquids. The other 20% is
found in food. Below are listed some foods and the
percentage of water that they contain.
iceberg lettuce 96%
squash, cooked. 90%
cantaloupe, raw, 90%
2% milk 89%
apple, raw 86%
cottage cheese 76%
potato, baked 75%
macaroni, cooked 66%
turkey, roasted 62%
steak, cooked 50%
cheese, cheddar 37%
bread, white 36%
peanuts, dry roasted 2%
Dehydration involves more than just water defi-
ciency.Electrolytesare ions that form when salts dis-
solve in water or body fluids. In order for cells to
function correctly, the various electrolytes, such as
sodium(Na+) and potassium (K+), must remain
within a very narrow range of concentrations. Often
electrolytes are lost along with water. For example
sodium is lost in sweat. To prevent the effects of dehy-
dration, both water and electrolytes must be replaced
in the correct proportions.DemographicsThe very young and the very old are most likely to
become dehydrated. Young children are at greater risk
because they are more likely to get diseases that cause
vomiting, diarrhea, and fever. Worldwide, dehydra-
tion is the leading cause of death in children. In the
United States, 400–500 children under the age of 5 die
every year of dehydration. The elderly are at risk
because they are less likely to drink when they become
dehydrated. The thirst mechanism often becomes less
sensitive as people age. Also, their kidneys lose the
ability to make highly concentrated urine. Older indi-
viduals who are confined to wheelchairs or bed and
cannot get water for themselves (e.g. nursing home
and hospital patients) are at risk of developing chronic
dehydration.Causes and symptomsDiarrhea, often accompanied by vomiting, is the
leading cause of dehydration. Both water and electro-
lytes are lost in large quantities. Diarrhea is often
caused by bacteria, viruses, or parasite. Fever that
often accompanies disease accelerates the amount of
water that is lost through the skin. The smaller the
child, the greater the risk of dehydration. Worldwide,
acute diarrhea accounts for the death of about 4 mil-
lion children each year. In the United States, about
220,000 children are hospitalized for dehydration
caused by diarrhea annually.
Heavy sweating also causes dehydration and loss
of electrolytes. Athletes, especially endurance athletes
and individuals with active outdoor professions such
such as roofers and road crew workers are at high risk
of becoming dehydrated. Children who play sports
can also be vulnerable to dehydration.
Certain chronic illnesses that disrupt fluid balance
can cause dehydration. Kidney disease and hormonal
disorders, such as diabetes, adrenal gland, or pituitary
gland disorders, can cause fluid and electrolyte loss
through excessive urination. Disorders such as cystic
fibrosis or other genetic disorders resultING in inad-
equate absorption of nutrients from the intestines can
cause chronic diarrhea that leads to dehydration. Indi-
viduals witheating disorderswho abuse laxatives,
diuretics, and enemas, or regularly cause themselves
to vomit are vulnerable to severe electrolyte imbalan-
ces and dehydration. The same is true of people with
alcoholism. People who have severe burns over a large
part of their body also are likely to become dehydratedKEY TERMS
Diabetes—a condition in which the body either
does not make or cannot respond to the hormone
insulin. As a result, the body cannot use glucose
(sugar). There are two types, type 1 and type 2.
Diuretic—a substance that removes water from the
body by increasing urine production
Electrolyte—ions in the body that participate in
metabolic reactions. The major human electrolytes
are sodium (Na+), potassium (K+), calcium (Ca 2+),
magnesium (Mg2+), chloride (Cl-), phosphate
(HPO 4 2-), bicarbonate (HCO 3 -), and sulfate
(SO 4 2-).
Laxative—A substance that stimulates movement
of food through the bowels. Laxatives are used to
treat constipation.Dehydration