Pregnancy: 60mg
Lactation: 70mg
Selenium in nutritional supplements is available
mostly in the form ofsodiumselenite and sodium
selenate, two inorganic forms of selenium or as sele-
nomethionine in ‘‘high selenium yeasts’’ generally con-
sidered to be the best absorbed and utilized form of
selenium.PrecautionsSelenium is trace element that is essential in small
amounts, but is toxic in larger amounts. Excessive
intake can result in symptoms that may include fatigue
and irritability, with increased toxicity leading to loss
of hair and nails, white blotchy nails, and garlic breath
odor. If not corrected, it leads to a condition called
chronic selenium toxicity (selenosis), with symptomsKEY TERMS
Amino acid—Organic (carbon–containing) mole-
cules that serve as the building blocks of proteins.
Antioxidant enzyme—An enzyme that can counter-
act the damaging effects of oxygen in tissues.
Cofactor—A compound that is essential for the
activity of an enzyme.
Blood brain barrier—A physiological mechanism
that alters the permeability of brain capillaries, so
that some substances, such as certain drugs, are
prevented from entering brain tissue, while other
substances are allowed to enter freely.
Enzyme—A biological catalyst, meaning a substance
that increases the speed of a chemical reaction with-
out being changed inthe overall process. Enzymes are
proteins and vitally important to the regulation of the
chemistry of cells and organisms.
Free radicals—Highly reactive chemicals that dam-
age components of cell membranes, proteins or
genetic material by ‘‘oxidizing’’ them, the same
chemical reaction that causes iron to rust.
Hormone—A chemical substance produced in the
body that controls and regulates the activity of cer-
tain cells or organs.
Immune system—Defense system of the body
responsible for protecting it against infections and
foreign substances.
Kashin–Beck disease—A disorder of the bones and
joints of the hands and fingers, elbows, knees, and
ankles of children and adolescents who slowly develop
stiff deformed joints, shortened limb length and short
stature. The disorder is endemic in some areas of east-
ern Siberia, Korea, China and Tibet.
Keshan’s disease—A potentially fatal form of cardi-
omyopathy (disease of the heart muscle).
Macro minerals—Minerals that are needed by the
body in relatively large amounts. They includesodium, potassium, chlorine, calcium, phosphorus,
magnesium.
Oxidative stress—Accumulation in the body of
destructive molecules such as free radicals that can
lead to cell death.
Peroxides—Peroxides are highly reactive free radi-
cal molecules, used as powerful bleaching agents
and as disinfectant. In the body, they form as inter-
mediate compounds, for example during the oxida-
tion of lipids, and may damage tissues.
Plasma—The liquid part of the blood and lymphatic
fluid, which makes up about half of its volume. It is
92% water, 7% protein and 1% minerals.
Reactive oxygen species (ROS)—Damaging mole-
cules, including oxygen radicals such as superoxide
radical and other highly reactive forms of oxygen that
can harm biomolecules and contribute to disease
states.
Reactive nitrogen species (RNS)—Highly reactive
chemicals, containing nitrogen, that react easily
with other molecules, resulting in potentially dam-
aging modifications.
Selenocysteine—Unusual amino acid consisting of
cysteine bound to selenium. The process of inserting
selenocysteine into proteins is unique to cysteine, and
occurs in organisms ranging from bacteria to man.
Selenoprotein—Enzyme that requires selenium to
function. At least eleven have been identified.
Thyroid—A gland located beneath the voice box
that produces thyroid hormone, a hormone that reg-
ulates growth and metabolism.
Trace minerals—Minerals needed by the body in
small amounts. They include: selenium, iron, zinc,
copper,manganese,molybdenum,chromium,arsenic,
germanium, lithium, rubidium, tin.Selenium