vitamins
organic compounds that are vital to life and indispensable to body functions but are needed only in minute amounts; noncaloric essential nutrients.
precursors, provitamins
compounds that can be converted into active vitamins.
beta-carotene
an orange pigment with antioxidant activity; a vitamin A precursor made by plants and stored in human fat tissue.
retinol
one of the active forms of vitamin A made from beta-carotene in animal and human bodies; an antioxidant nutrient.
retina
the layer of light-senitive nerve cells lining the back of the inside of the eye.
cornea
the hard, transparent membrane covering the outside of the eye.
rhodopsin
the light-sensitive pigment of the cells in the retina; it contains vitamin A.
night blindness
slow recovery of vision after exposure to flashes of bright light at night; an early symptom of vitamin A deficiency.
keratin
the normal protein of hair and nails.
keratinization
accumulation of keratin in a tissue; a sign of vitamin A deficiency.
xerosis
drying of the cornea; a symptom of vitamin A deficiency.
xerophthalmia
progressive hardening of the cornea of the eye in advanced vitamin A deficiency that can lead to blindness.
epithelial tissue
the layers of the body that serve as selective barriers to environmental factors.
cell differentiation
the process by which immature cells are stimulated to mature and gain the ability to perform functions characteristic of their cell type.
carotenoid
a member of a group of pigments in foods that range in color from light yellow to reddish orange and are chemical relatives of beta-carotene.
macular degeneration
a common, progressive loss of function of the part of the retina that is most crucial to focused vision. This degeneration often leads to blindness.
dietary antioxidants
compounds typically found in plant foods that significantly decrease the adverse effects of oxidation on living tissues.
retinol activity equivalents (RAE)
a new measure of the vitamin A activity of beta-carotene and other vitamin A precursors that reflects the amount of retinol that the body will derive from a food containing vitamin A precursor compounds.
IU (international units)
a measure of fat-soluble vitamin activity sometimes used in food composition tables and on supplement labels.
rickets
the vitamin D deficiency disease in children; characterized by abnormal growth of bone and manifested in bowed legs or knock-knees, outward-bowed chest, and knobs on the ribs.
osteomalacia
the adult expression of vitamin D deficiency disease, characterized by an overabundance of unmineralized bone protein.
osteoporosis
a weakening of bone mineral structures that occurs commonly with advancing age.
tocopherol
a kind of alcohol.
free radicals
atoms or molecules with one or more unpaired electrons that make the atom or molecule unstable and highly reactive.
erythrocyte hemolysis
rupture of red blood cells, caused by vitamin E deficiency.
jaundice
yellowing of the skin due to spillover of the bile pigment bilirubin from the liver into the general circulation.
scurvy
the vitamin C-deficiency disease.
ascorbic acid
one of the active forms of vitamin C; an antioxidant nutrient.
collagen
the chief protein of most connective tissues, including scars, ligaments, and tendons, and the underlying matrix on which bones and teeth are built.
prooxidant
a compound that triggers reactions involving oxygen.
coenzyme
a small molecule that works with an enzyme to promote the enzyme's activity.
thiamin
a B vitamin involved in the body's use of fuels.
beriberi
the thiamin-deficiency disease; characterized by loss of sensation in the hands and feet, muscular weakness, advancing paralysis, and abnormal heart action.
riboflavin
a B vitamin active in the body's energy-releasing mechanisms.
niacin
a B vitamin needed in energy metabolism; can be eaten preformed or can be made in the body from tryptophan, one of the amino acids.
pellagra
the niacin-deficiency disease. symptoms include the 4 D's.
niacin equivalents (NE)
the amount of niacin present in food, including the niacin that can theoretically be made from its precursor tryptophan and that is present in the food.
folate
a B vitamin that acts as part of a coenzyme important in the manufacture of new cells.
neural tube defects (NTD)
abnormalities of the brain and spinal cord apparent at birth and believed to be related to a woman's folate intake before and during pregnancy.
dietary folate equivalent (DFE)
a unit of measure expressing the amount of folate available to the body from naturally occurring sources.
vitamin B12
a B vitamin that helps to convert folate to its active form and also helps maintain the sheath around nerve cells.
intrinsic factor
a factor found inside a system.
pernicious anemia
a vitamin B12 deficiency disease, cause by lack of intrinsic factor and characterized by large, immature red blood cells and damage to the nervous system.
vitamin B6
a B vitamin needed in protein metabolism.
serotonin
a neurotransmitter important in sleep regulation, appetite control, and mood regulation, among other roles.
carpal tunnel syndrome
a pinched nerve at the wrist, causing pain or numbness in the hand.
biotin
a B vitamin; a coenzyme necessary for fat synthesis and other metabolic reactions.
pantothenic acid
a B vitamin.
choline
a nonessential nutrient used to make the phospholipid lecithin and other molecules.
carnitine
a nonessential nutrient that functions in cellular activities.
inositol
a nonessential nutrient found in cell membranes.
lipoic acid
a nonessential nutrient.