ORGANIZATIONS
North American Association for the Study of Obesity
(NAASO), The Obesity Society. 8630 Fenton Street,
Suite 918, Silver Spring, MD 20910. Telephone: (301)
563-6526. Website: http://www.naaso.org.
Rudd Center for Food Policy and Obesity. 309 Edwards
Street, Yale University, New Haven, CT 06520-8369.
Telephone: (203) 432-6700. Website: http://www.yaler
uddcenter.org/home.aspx.
Slim-Fast Foods Company. Website: http://www.slim-fast
.com/index.asp. Contact by e-mail only, at http://
http://www.slim-fast.com/contact/comments.asp. Telephone
line for nutritional advice: (800) 754-6327.Rebecca J. Frey, Ph.D.Sodium
Definition
Sodium is a mineral that exists in the body as the ion
Na+. Sodium is acquired through diet, mainly in the form
of salt (sodium chloride, NaCl). Regulating the amount of
Na+ in the body is absolutely critical to life and health.Purpose
Sodium is possibly the most important mineral in
the body. It plays a major role in controlling the dis-
tribution of fluids, maintaining blood pressure and
blood volume, creating an electrical gradient that
allows nerve transmission and muscle contraction to
occur, maintaining the mechanisms that allow wastes
to leave cells, and regulating the acidity (pH) of the
blood. Many different organ working together, includ-
ing the kidneys, endocrine glands, and brain, tightly
control the level of Na+ in the body. Researchers
estimate that between 20% and 40% of an adult’s rest-
ing energy use goes toward regulating sodium. Sodium
affects every cell in the body, and a major failure of
sodium regulatory mechanisms means death.Description
In the body, sodium exists as electrolyte.Electro-
lytesare ions that form when salts dissolve inwateror
fluids. These ions have an electric charge. Positively
charged ions are called cations. Negatively charged
ions are called anions. Electrolytes are not evenly dis-
tributed within the body, and their uneven distribution
allows many important metabolic reactions to occur.
Sodium (Na+), potassium (K+),calcium(Ca 2+),
magnesium (Mg 2+), chloride (Cl-), phosphate(HPO 4 2-), bicarbonate (HCO 3 -), and sulfate (SO 4 2-)
are important electrolytes in humans.
Na+ is ten times more concentrated in fluid out-
side cells (i.e. extracellular fluid and blood) than it is in
fluid inside cells. This difference in concentration is
maintained through the expenditure of cellular energy,
and it is critical to many metabolic functions, including
maintaining the proportion of water that exists inside
and outside of cells. (See the entry on electrolytes for a
more detailed explanation of how this occurs). When
Na+ is too high or too low, it is almost never because
an individual has eaten too much or too little salt.
Instead, it is because organs such as the kidneys or
endocrine glands that regulate the conservation or
removal of sodium from the body have broken down.Sodium requirements
Researchers estimate that humans can remain
healthy taking in only 500 mg of sodium daily. Salt is
40% sodium by weight, and 500 mg is slightly less than
the amount of sodium found in 1/4 teaspoon of salt.
Humans almost never take in too little salt; their
health problems result from too much salt in the diet.
The United States Institute of Medicine (IOM) of
the National Academy of Sciences has developed val-
ues calledDietary Reference Intakes(DRIs) for many
vitaminsandmineralsincluding sodium. The DRIsSodiumAge Adequate Intake (mg)
Children 0−6 mos. 120
Children 7−12 mos. 370
Children 1−3 yrs. 1,000
Children 4−8 yrs. 1,200
Children 9−13 yrs. 1,500
Adolescents 14−18 yrs. 1,500
Adults 19−50 yrs. 1,500
Adults 51−70 yrs. 1,300
Adults 71 yrs. 1,200
Pregnant women 1,500
Breastfeeding women 1,500
Food Sodium (mg)
Table salt, 1 tsp. 2,300
Dill pickle, 1 large 1,731
Chicken noodle soup, canned, 1 cup 850–1,100
Ham, 3 oz. 1,000
Sauerkraut, ½ cup 780
Pretzels, 1 oz. 500
Turkey breast, deli, 1 oz. 335
Soy sauce, 1 tsp. 304
Potato chips, 1 oz. 165–185
mg milligram(Illustration by GGS Information Services/Thomson Gale.)Sodium