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Definition Page for DrumLib's Health Research Review:
Vitamin A
SYN: Retinol
A fat-soluble vitamin found primarily in animal food; the
precursors, carotenes, are found in plants. Vitamin A is required for night vision because
of its role in the synthesis of rhodopsin. Thyroid hormones
promote the synthesis of vitamin A from carotene. If your skin becomes yellow from a
moderate dose of beta carotene, you may be hypothyroid. The
old form of measurement for vitamin A, international units (IU), has been replaced by
retinol equivalents (RE). The conversion is easy: 1 microgram (mcg) RE equals 3.3 IU
retinol.
Vitamin B-2
SYN: Riboflavin (RYE-boe-flay-vin)
A water soluble B vitamin that is required for the formation of
red blood cells and antibody production. Riboflavin is absorbed in
the upper GI tract by an active transport process. The biologically active forms of
riboflavin are its coenzyme forms: flavin mononucleotide (FMN) and flavin adenine
dinucleotide (FAD). These coenzymes are involved in mitochondrial
energy production. Their activity is regulated (in part) by triiodothyronine (T3): FMN is inhibited in hypothyroidism and increased
in hyperthyroidism.
SEE: Thyroid gland
Vitamin B-3
SYN: Niacin
SYN: Niacinamide
SYN: Nicotinic acid
A water-soluble vitamin that is partly supplied by conversion of
the amino acid tryptophan.
Dietary niacin is hydrolyzed by enzymes in the intestinal mucosa
to yield nicotinamide, which is the amide of nicotinic acid. Niacin is involved in the use
of glycogen and fatty acids
for the bodies energy needs. Niacin is part of two important enzymes: nicotinamide adenine
dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP).
Vitamin B-5
SYN: Pantothenic acid (pan-toe-THEN-ik)
SYN: Pantothenate
A water-soluble vitamin that is sometimes called an
"anti-stress" supplement. Vitamin B-5 is converted to coenzyme A, which is a
catalyst of acetylation reactions and is involved in the synthesis of the
neurotransmitter, acetylcholine. Coenzyme A also plays
an important role in the synthesis of phospholipids, cholesterol, and the numerous
biochemicals that are made from cholesterol (e.g., steroid hormones and vitamin D). Vitamin B-5 is also involved in the metabolism of
carbohydrates, fats, and protein.
Vitamin B-6
SYN: Pyridoxal (pi-ri-DOKS-al)
SYN: Pyridoxamine
SYN: Pyridoxine (pi-ri-DOKS-een)
A water-soluble vitamin that is intimately involved in amino acid metabolism. Vitamin B-6 is needed for the
interconversion of sulfur amino acids. Both noradrenaline and acetylcholine are dependent on vitamin B-6. Vitamin B-6 is
also a cofactor for enzymes called transaminases, which are involved in the metabolism of
amino acids. There is a coenzyme form of vitamin B-6,
pyridoxal phosphate, that transports several amino acid groups. Pyridoxal phosphate is
also involved in decarboxylation reactions (e.g., converting tryptophan
into serotonin) and the methylation of methionine, choline, and serine.
Vitamin B-12
SYN: Cobalamin (coe-BALL-ah-min)
A water-soluble vitamin that is part of a number of coenzymes that are needed by rapid-turnover cells. Vitamin B-12
contains cobalt, which gives it a dark red color. Vitamin B-12 helps to lower homocysteine levels: A methyl group is removed from methyl
folate (folic acid) and transferred to homocysteine and methionine is formed. Like many B-vitamins, B-12 plays an
important role in the synthesis of neurotransmitters.
The absorption of vitamin B-12 is dependent upon gastric secretion of a mucoprotein called
intrinsic factor. People with inadequate intrinsic factor often benefit from injections of
vitamin B-12.
Vitamin C
SYN: Ascorbate
SYN: Ascorbic acid
A water soluble antioxidant that plays an important role in
collagen formation and immune function.
Vitamin D
SYN: Calciferol (cal-SIF-er-ol)
SYN: Ergocalciferol (ER-go-cal-SIF-er-ol)
A fat-soluble vitamin that regulates calcium and phosphorus
metabolism. Vitamin D is absorbed primarily in the duodenum and the overall efficiency of
absorption is about 50%. In the liver, vitamin D is converted (by vitamin
D-25-hydroxylase) into the highly active calcitriol (25-hydroxyvitamin D), which is
transported through the body by a carrier protein.
Ergocalciferol (vitamin D2) is of plant origin. Calciferol
(vitamin D3) is found in animals, especially in the livers of fish.
Vitamin E
SYN: Tocopherol (toe-KOE-fer-ol)
SYN: Tocotrienol (toe-koe-TRY-en-ol)
There are two main groups of vitamin E molecules (tocopherol and
tocotrienol). Each group contains the alpha, beta, delta, and gamma forms. Alpha
tocopherol has the most vitamin E activity. Vitamin E is fat soluble and poorly absorbed
(about 20-40 percent). Vitamin E is primarily absorbed in the median portion of the small
intestine. The human body stores about 40 mg/kg and 77 percent of the vitamin E is stored
in adipose (fat) tissue.
Vitamin K
SYN: (Natural) Phylloquinone (fil-oh-KWIN-own)
SYN: (Natural) Phytonadione (FIE-toe-nay-DIE-own)
SYN: (Synthetic) Menadione (men-ah-DIE-own)
SYN: (Synthetic) Menaquinone (men-ah-KWIN-own)
SYN: (Synthetic) Menaphthone (men-ah-NAF-thown)
SYN: (Synthetic) Menadiol sodium diphosphate (men-ah-DIE-ol die-FOSS-fate)
Phylloquinone is the main form of vitamin K found in plants. It
was isolated from alfalfa. Phylloquinone is also called phytonadione; both refer to
natural vitamin K. Menadione is a synthetic vitamin K that is taken in tablet form or used
parenterally in oil. Menadiol sodium diphosphate is a
synthetic water-soluble form of vitamin K.
Adult males need a minimum of 80 micrograms of vitamin K per day;
adult females need 65. Children need about one third of the adult requirements.
Approximately half of the vitamin K that we need is produced by intestinal bacteria.
Natural vitamin K is a fat-soluble vitamin that is required for
two bone matrix proteins and the following coagulation
(blood clotting) factors: prothrombin, proconvertin (Factor VII), Stuart-Prower factor
(Factor X), Christmas factor (Factor IX). The following anticoagulants
are also vitamin K-dependent: protein C, protein S, and protein Z.
Green leafy vegetables are a good food source of vitamin K.
Typically, supplements contain 100 micrograms of natural vitamin K. I would avoid the
synthetic forms because they can be toxic -- especially in children. Menadione is a
provitamin K that combines with sulfhydryl groups in membranes and can cause jaundice, hemolysis, and kernicterus.
Don't take anything but natural vitamin K.