| vitamin | Compound needed in very small
amounts in the diet to help regulate and
support chemical reactions and processes in
the body.
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| fat-soluble vitamins | Vitamins that dissolve
in fat and such substances as ether and benzene
but not readily in water. These vitamins
are A, D, E, and K.
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| water-soluble vitamins | Vitamins that dissolve
in water. These vitamins are the B vitamins
and vitamin C.
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| coenzyme | A compound that combines with
an inactive enzyme to form a catalytically
active form. In this manner, coenzymes aid
in enzyme function.
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| megadose | Intake of a nutrient beyond
estimates of needs to prevent a deficiency, or
what would be found in a balanced diet; 3 to
10 times human needs is a starting point for
such a dosage.
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| retinoids | Chemical forms of preformed
vitamin A; one source is animal foods.
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| carotenoids | Pigment materials in fruits and
vegetables that range in color from yellow to
orange to red; three of the various carotenoids
yield vitamin A. Many are antioxidants.
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| provitamin A | A substance that can be
made into a vitamin.
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| night blindness | A vitamin A deficiency condition
in which the retina (in the eye) cannot
adjust to low amounts of light.
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| mucus | A thick fluid secreted by many cells
throughout the body. It contains a compound
that has both carbohydrate and protein parts.
It acts as a lubricant and means of protection
for cells.
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| xerophthalmia | Literally "dry eye." This is a
cause of blindness that results from a vitamin
A deficiency. The specific cause is linked to a
lack of mucus production by the eye, which
then leaves it at a greater risk of damage from
surface dirt and bacteria.
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| macular degeneration | A painless condition
leading to disruption of the central part of
the retina (in the eye) and, in turn, blurred
vision.
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| epithelial cells | The cells that line the
outside of the body and the inside of all
external passages within it, such as the
GI tract.
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| gene expression | Use of DNA information
on a gene to produce a protein. This is a
major determinant of cell development.
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| prostate gland | A solid, chestnut-shaped
organ surrounding the first part of the urinary
tract in the male. The prostate gland secretes
substances into the semen.
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| analog | A chemical compound that differs
slightly from another, usually natural,
compound. Analogs generally contain extra or
altered chemical groups and may have similar
or opposite metabolic effects compared with
the native compound. Also spelled analogue.
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| international unit (IU) | A crude measure of
vitamin activity, often based on the growth
rate of animals in response to the vitamin.
Today IUs have largely been replaced by more
precise milligram or microgram measures.
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| fetus | The developing human life form from
8 weeks after conception until birth.
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| parathyroid hormone (PTH) | A hormone
made by the parathyroid glands that increases
synthesis of the vitamin D hormone and aids
calcium release from bone and calcium
conservation by the kidneys, among other
functions.
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| rickets | A disease characterized by poor
mineralization of newly synthesized bones
because of low calcium content. This defi-
ciency disease arises in infants and children
from insufficient amounts of the vitamin D
hormone in the body.
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| osteomalacia | Adult form of rickets. The
weakening of the bones that is seen in this
disease is caused by low calcium content. A
reduction in the amount of the vitamin D
hormone in the body is one cause.
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| hemolysis | Destruction of red blood cells.
The red blood cell membrane breaks down,
allowing cell contents to leak into the fluid
portion of the blood.
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| tocopherols | The chemical name for some
forms of vitamin E. The alpha form is the
most potent.
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| isomers | Different chemical structures for
compounds that share the same chemical
formula.
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| hemorrhage | An escape of blood from
blood vessels.
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| coagulation | Blood clotting; essentially a
transition of blood from a liquid cell suspension
into a solid, gel-like form.
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| bioavailability | The degree to which an
ingested nutrient is absorbed and thus is
available to the body.
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| beriberi | The thiamin deficiency disorder
characterized by muscle weakness, loss of
appetite, nerve degeneration, and sometimes
edema.
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| dementia | A general loss or decrease in
mental function.
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| premenstrual syndrome (PMS) | A disorder
found in some women a few days before a
menstrual period begins. It is characterized by
depression, anxiety, headache, bloating, and
mood swings. Severe cases are currently
termed premenstrual dysphoric disorder
(PDD).
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| megaloblast | A large, immature red blood
cell that results from the particular cell’s
inability to divide normally.
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| erythrocytes | Mature red blood cells. These
have no nucleus and a life span of about
120 days; they contain hemoglobin, which
transports oxygen and carbon dioxide.
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| macrocytic anemia | Anemia characterized
by the presence of abnormally large red blood
cells.
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| neural tube defect | A defect in the formation
of the neural tube occurring during early
fetal development. This type of defect results
in various nervous system disorders, such as
spina bifida. Folate deficiency in the pregnant
woman increases the risk that the fetus will
develop this disorder.
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| intrinsic factor | A protein-like compound
produced by the stomach that enhances
vitamin B-12 absorption.
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| pernicious anemia | The anemia that results
from a lack of vitamin B-12 absorption; it is
pernicious because of associated nerve
degeneration that can result in eventual
paralysis and death.
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| lecithin | A group of phospholipid compounds
that are major components of cell
membranes.
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