Vitamins are organic compounds that are necessary for life required in
small amounts and must be obtained in the diet (except for vitamin D which
can be made with the aid of sunlight) as the body cannot make them from
other nutrients. In this definition, "organic" refers to the fact that they
contain carbon atoms and has nothing to do with the fertilizers used to
nourish the foods from which they are derived or whether or not they are
grown with or without pesticides. Vitamins A, D, E and K are fat-soluble
vitamins. The B-complex vitamins and vitamin C are water-soluble vitamins.
Vitamin A has many different functions. First it is related to the
maintenance of normal vision in dim light or the prevention of night
blindness. It also aids in the growth and formation of body cells, making it
essential for body growth. It is especially needed for bone growth. If the
intake is not sufficient, bones will stop growing before the soft tissues
are fully mature. Vitamin A is also needed for normal tooth development
because the enamel-forming cells are affected by lack of vitamin A. It is
also important in the maintenance of healthy epithelial tissues. There are
two kinds of epithelial tissues: (1) those that cover the outer surface of
the body -- the resistant, protective skin (epidermis), and (2) those that
line all the mucous membranes. Without vitamin A, the epithelial cells
become dry and flat and gradually harden to form scales that shed. Vitamin A
is also necessary for the health of the membranes lining the stomach,
intestinal wall, bladder and urinary passages and for the health of the sex
glands and uterus. Lastly, vitamin A works better when there are sufficient
body levels of zinc and an adequate intake of protein.
Vitamin D is required for calcium and phosphorus absorption and
utilization. It is necessary for growth, development and maintenance of
bones and teeth in adults and children. In its active form, vitamin D works
with calcium to control bone formation. Vitamin D is unique in that man and
animals normally obtain it from two sources: the spontaneous formation in
the skin by the sun via a photochemical reaction in the epidermis and the
ingestion of a food source that contains vitamin D through the mouth.
Vitamin E (alpha tocopherol) prevents saturated fatty acids and vitamin A
from breaking down and combining with other substances that may become
harmful to the body. Not surprisingly, fats and oils containing vitamin E
are less susceptible to rancidity than those devoid of vitamin E. Vitamin E
also has the ability to unite with oxygen and prevent it from being
converted into toxic peroxides. This leaves the red blood cells more fully
supplied with the pure oxygen that the blood carries to the heart and other
organs.
Vitamin E plays an essential role in cellular
respiration of all muscles, especially cardiac and skeletal. Vitamin E makes
it possible for these muscles and their nerves to function with less oxygen,
thereby increasing their endurance and stamina. It also causes dilation of
the blood vessels, permitting a fuller flow of blood to the heart. Vitamin E
also aids in bringing nourishment to the cells, strengthening the capillary
walls, and protecting the red blood cells from destruction by poisons such
as, hydrogen peroxide, in the blood.
The general term "Vitamin K" is used to describe a group of natural
fat-soluble quinone compounds having anti-hemorrhagic effects. The
designation vitamin "K" may have been selected because it was the first
letter of the alphabet that was not in use for a proven or postulated
vitamin at the time of discovery, but it is also the first letter of the
German word, "koagulation," Vitamin K is important for proper blood clotting
or coagulation in humans. It is essential for the synthesis by the liver of
prothrombin, factors VII, IX and X, and proteins C and S, which are all
involved in the regulation of blood clotting. Without vitamin K, the level
of the blood clotting proteins in the blood is reduced and clotting time is
prolonged. Vitamin K also has a role in the maintenance and health of bone
(Gla calcium-binding proteins osteocalcin, MGP, and Protein S) and vascular
biology (MGP, Protein S and Gas-6). Biochemically, vitamin K is involved in
the conversion of glutamate residues into certain proteins called
gamma-carboxyglutamic acids (Gla).
The first compound shown to have vitamin K activity is a complex molecule
called 2-methyl-3-phytyl-1,4-naphthoquinone, which nutritionists simply call
"phylloquinone" or "vitamin K1." The United States Pharmacopoeia (USP) calls
this same compound "phytonadione." Vitamin K1 was first isolated from
alfalfa. A second form of vitamin K was isolated from putrefied fish meal
and called menaquinone or vitamin K2. Vitamin K2 now refers to any of the
series of vitamin K compounds having unsaturated side chains, which are
found in animals and bacteria. The first vitamin K2 isolated is now called
menaquinone-7 (MK-7) as it has seven isoprenoid units. It is interesting to
note that chemical structure of vitamin K2 is somewhat similar to the
structure of coenzyme Q10. There is a synthetic compound called vitamin K3
that is approved for use in animals. Vitamin K3 is called menadione and is a
simpler compound not having the isoprenoid side chain.
Vitamin K1 has a tendency to be transported to the liver, whereas vitamin K2
has a tendency to be transported to other tissues. The vitamin K transported
to the liver become involved in the regulation of blood coagulation, whereas
the vitamin K transported to other tissues becomes involved in regulation of
cell growth and differentiation, and in metabolism and regulation of soft
tissue calcification.
Vitamin K is found in both plant and animal sources in nature. Good plant
sources of vitamin K1 include dark leafy greens, most green plants, alfalfa
and kelp. Blackstrap molasses and the polyunsaturated oils such as,
safflower, also contain some vitamin K. Good animal sources of vitamin K2
include liver, cheese, milk, yogurt, egg yolks nado, and fish liver oils.
The best source for humans is that made by the intestinal bacteria which is
why vitamin K supplementation is particularly important for those whose
normal balance of intestinal bacterial flora has been disrupted. The B
vitamins consist of a large number of substances that are involved in the
metabolism of all living cells. Acting as coenzymes, they work together with
proteins in the various enzyme systems of our body.
The functions of the B vitamins are closely synergistic and because of
these interrelationships, an insufficient intake of one or more of them can
cause deficiencies in the others by hampering their utilization. B vitamins
are water-soluble and are not stored in the body. They must be replaced
daily and any excess excreted.
Although the B vitamins do work together, some of their individual
functions are as follows:
Vitamin B-1 (thiamine) acts as a coenzyme necessary for the conversion of
carbohydrates into glucose, which is burned in the body for energy. It is
essential for the functioning of the nervous system. A deficiency can cause
beriberi, a disease marked by weakness, paralysis and edema.
Vitamin B-2 (riboflavin) acts as a coenzyme that activates the breakdown
and utilization of carbohydrates, fats and proteins. It is essential for
cellular oxidation. A deficiency can cause tissue inflammation and an
over-sensitivity to bright light.
Vitamin B-6 (pyridoxine) plays a role as a coenzyme in the breakdown and
utilization of carbohydrates, fats and proteins. It facilitates the release
of glycogen for energy from the liver and muscles. It also participates in
the utilization of energy in brain and nervous tissue and is essential for
the regulation of the central nervous system.
Vitamin B-12 (cobalamin) is the only vitamin containing cobalt, a trace
mineral. It is essential for the normal functioning of all body cells,
especially those of the bone marrow, gastrointestinal tract and nervous
system. It is also necessary for the formation of red blood cells.
Biotin is an essential coenzyme that assists in the making of fatty acids
and in the burning of carbohydrates and fats for body heat and energy. It
also aids in the utilization of amino acids, folic acid, pantothenic acid
and vitamin B-12. It is also a potent stimulant to the growth of healthy
cells.
Choline is usually considered part of the vitamin B complex. It is a
component of lecithin, which facilitates the movement of fat from the liver
and into cells, and it must be present before vitamin A can be stored. It is
manufactured in the body from dietary phosphatides as found in lecithin.
Folic acid functions along with vitamins B-12 and C in the utilization of
proteins. It has an essential role in the formation of heme, the iron
containing protein in hemoglobin necessary for the formation of red blood
cells. Some folic acid is produced by the intestinal bacteria. Folic acid is
essential during pregnancy to prevent neural tubular defects in the
developing fetus.
Inositol is usually considered part of the vitamin B complex. It is
thought that, along with choline, inositol is necessary for the formation of
lecithin within the body.
Niacin, also available in the form of niacinamide, is a coenzyme that
assists in the breakdown of carbohydrates, fats and proteins. Niacin is
essential for the health of the skin, tongue and digestive system. The
disease, pellagra, is a result of a niacin deficiency.
PABA (para-aminobenzoic acid) may be considered part of the vitamin B
complex. It influences intestinal bacteria, enabling them to produce folic
acid, which in turn, aids in the production of pantothenic acid. As a
coenzyme, PABA functions in the breakdown and utilization of proteins, and
aids in the formation of red blood cells.
Pantothenic acid is necessary for the normal functioning
of the adrenal gland which directly affects growth. It is also essential for
the formation of fatty acids. In addition, as a coenzyme, it participates in
the utilization of riboflavin and in the release of energy from
carbohydrates, fats and proteins.
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