Origin and History
of Vitamins
Vitamin, Basics. We have all gazed at the cereal box label
during breakfast when we were children and wondered what words like vitamins,
folic acid and riboflavin meant. We wondered why our parents
insisted that we drink plenty of milk, eat red meat, and finish our green
vegetables.Of course; we now realize that the information on the cereal box and
the advice of our parents were both related to vitamins. In this class, we
shall explore the little understood world of vitamins and why they are
necessary to human health.
Our brief journey
into the history of vitamins starts almost 3500 years ago, when the ancient
Egyptians discovered that night blindness could be treated with certain foods. Despite
this early wisdom, much of the ancient knowledge gathered about vitamins was forgotten
down through the centuries. During the Middle Ages, diseases were commonly attributed
to witchcraft, bad air, angry Gods, spontaneous afflictions and so forth. It is
primarily because of comparatively recent advances in the work of molecular
biologists that we today have a good understanding of vitamins and other
nutrients.
One of the major
milestone in nutritional medicine occurred in 1747, when Scottish surgeon James
Lind discovered an unknown nutrient that we today call Vitamin C. He found that
scurvy, a widely reported disease characterized by spontaneous bleeding, loose
teeth, aching joints and lack of energy, could be prevented by taking citrus
foods. Unfortunately, his discovery was largely ignored, and over the next
forty years, thousands of people died from scurvy. In the 1860s, Louis Pasteur
discovered that microscopic organisms caused many diseases. His discoveries
prompted further research into the curative and preventative properties of vitamins.
As recently as the
early 1900s, numerous diseases such as beriberi and pellagra were still regarded as
infectious diseases rather than nutritional deficiencies. From the initial
discovery of vitamins in 1911 through the 1950s, nearly all physicians around
the world based their studies and diagnoses on vitamin deficiencies. During the
1940s and 1950s, a number of researchers began to lay the foundation for a new
era in vitamins. Much of our present-day knowledge evolved from the works of
these scientists. The future of nutritional medicine holds wondrous
possibilities for mankind, and as our knowledge of vitamins and other nutrients
expands further, we will no doubt discover that vitamins have even greater
value and utility than we presently imagine. Our view and vision of nutrition
and vitamins may be limited by what we know today, but we should leave our door
open for what we have not yet discovered. In fact, it is quite likely that some
vitamins have yet to be discovered.
Before we delve
into vitamins, we must first understand the concept of nutrients. To function,
the human body must have nutrients. The nutrients known to be essential for human
well being are: proteins, carbohydrates, fats and oils, minerals, vitamins, and
water. Vitamins are a group of substances that are essential for normal
metabolism, growth and development, and regulation of cell function. The word
vitamin derives from the words vital and amine. Vitamins are
organic (that is, carbon containing) molecules which mainly act as a catalysts
in our body All naturally occurring vitamins are organic food substances that
are found only in living things; that is, plants and animals. With a few
notable exceptions, the human body cannot manufacture or synthesize vitamins on
its own. Vitamins must be supplied in the diet or in dietary supplements.
Vitamins help to
regulate the metabolism. They also help convert fat and carbohydrates into
energy and assist in the formation of healthy bones and tissues. In addition,
vitamins provide vitality
and general well being. Vitamins can be used to effectively treat and cure
nutritional based deficiencies. Although vitamins do not prevent or cure other
types of invasive diseases such as cancer, afflictions related to aging, or
biological infections, a diet that supplies the proper balance of essential vitamins
and nutrients can help fortify the immune system and thus provide some
beneficial protection against such diseases. It is likely that future
discoveries will shed new light on vitamins and their important role in human
disease and aging. It is important to understand that vitamins cannot replace
food. In fact, vitamins cannot be assimilated without ingesting food. That is
why doctors and advocates of natural nutrition stress that vitamins must be taken
with meals. Vitamins work together with enzymes, co factors and other substances
in the digestive tract. As I stated earlier, the body cannot create vitamin
molecules itself, so these molecules must come through food that we eat. As a
general rule, vitamins are destroyed by heat, exposure to air, sunlight, and
oxidizing conditions. Improper storage conditions can allow mold growth. If
mixed into other foods, vitamins should always be consumed within a couple of
days at most. Researchers have found that the requirement of vitamins varies
from one person to another, and that psychological stress can rapidly delete
the body's vitamin reserves. With a few notable exceptions, it is better to
have an excess of vitamins in the body than to be deficient. Vitamin
supplements are readily available at health food stores, pharmacies and grocery
stores, and are usually inexpensive.
Each vitamin plays
a specific role in the human body. In many cases, vitamins must interact with
other vitamins to function properly, and a lack or excess of any one of then
can disturb the assimilation of another vitamins. Thus, taking multivitamin
formulas where there is too much of one vitamin and too little of another can
have less than desirable results. Poorly balanced multivitamin formulas can
even cause vitamin deficiencies. The foregoing vitamins are digested and
absorbed with the help of fats occurring naturally in the diet. Fat soluble
vitamins can be stored in the body for long periods of time. They are stored
mostly in the fatty tissues and in the liver. Hence, supplementation are not
required as frequently as with water-soluble vitamins. However, in emotionally
stressful conditions, supplementation becomes important. Because fat soluble
vitamins are stored in the body, it is possible to overdose by taking too much
of these vitamins. Care must be taken to ensure that safe dosage levels are not
exceeded.
Where do vitamins
come from and how much of each vitamin is recommended? The two primary sources
of vitamins for human consumption are in plants and in animal tissues. Unfortunately,
the amount of vitamin that one can expect to derived from a given source can
vary, depending on a variety of circumstances. For example, in plants, the
vitamin yield will vary depending on:
1. How the plant
is harvested and processed. Often, nutrients are leached out ofthe plant during
processing and the "food" that results has little or no nutritional
value.
2. The part of
the plant being processed will affect vitamin levels to a significant degree.
3. The species of
the plant will also affect vitamin content. Some hybrid plants that produce a
higher yield per acre and can be harvested sooner are more profitable for
farmers yet exhibit markedly reduced vitamin content. In Animal tissues, the
primary sources of vitamins are:
1. Liver
2. Kidney
Various other
meat, poultry and fish products also provide vitamin nutrients but to a lesser degree.
In addition, the human body produces limited amounts of Vitamins K and B from bacteria
within the intestines; and Vitamin D is formed with the help of ultraviolet
radiation or sunshine on the skin.
Recommended Daily
Allowances (RDA)
The best way to
ensure that your body gets the daily requirement of vitamins is to eat a balanced
diet, which contains a variety of foods. The daily recommended levels of
vitamins are often referred as the RDA or Recommended Daily Allowances. RDA
are defined as the levels of intake of nutrients that, on the basis of current
scientific knowledge, the Food and Nutrition Board regard as adequate to meet
the known nutritional needs of most healthy people. However, determine RDA for
each vitamin is not that simple. Specific requirements may vary depending on
age, gender, and a multitude of other factors such as pregnancy, stress, work
and sleep habits, presence of disease or degenerative conditions, and other health and lifestyle considerations.
Vitamin overdose, side effects and toxicity
Overdosage of
certain vitamins may cause some side effects. Therefore, the supplementation of
vitamins should be safely dosed with the guides of a reliable medical
instruction. Excessive intake of vitamin A can be harmful to bones and skin,
causing weakness and brittleness.Large doses of niacin
can cause liver damage, peptic ulcers, and skin rashes. Vitamin B6 toxicity can
damage sensory nerves. High doses of PABA can cause blood sugar to drop. There
is a high health risk associated with consuming too much vitamin D.
ALL ABOUT VITAMINS: ONE
MUST KNOW:-
Vitamin: The group of organic substances that are required
in the diet of humans and animals for normal growth, maintenance of life, and
normal reproduction. Vitamins act as catalysts; very often either the vitamins
themselves are co enzymes biotin, is a member of the B complex; it was
first isolated in 1935 from dried egg yolk, and its structure was established
in 1942. Biotin is usually found attached to a lysine residue in certain
enzymes, where it participates in reactions involving the transfer of carboxyl (COOH) groups;
one such reaction
is essential for
the synthesis of
fatty acids. or they form
integral parts of co enzymes. A substance that functions as a vitamin for one
species does not necessarily function as a vitamin for another species. The
vitamins differ in structure, and there is no chemical grouping common to them
all.
They were first
called accessory factors because in 1906 it was found by English biochemist Sir
F.G. Hopkins, Sir Frederick Gowland,1861.1947,English biochemist, educated at
Cambridge and the Univ. of London. He
was professor of biochemistry at Cambridge
(1914.43) Among his contributions were important studies in carbohydrate metabolism
and muscular activity, including the discovery of the relationship of
lactic-acid formation to
muscular contraction, that most foods contain. besides carbohydrates, proteins,
fats, minerals, and water.other substances necessary for health. The word vitamin
was derived from the term vitamine, used by Polish-American biochemist
Casimir Funk, Casimir (kãz`ĭmçr f
ngk),1884.1967, American biochemist, to describe an amine
(organic base) that was essential to life (it was later found to be thiamine).
In 1912 Hopkins and Funk formulated the vitamin hypothesis of deficiency disease;
that is, that certain diseases are caused by a dietary lack of specific
vitamins. The chemical structures of the vitamins are all known, and all of
them have been synthesized; the vitamins in foods are identical to the
synthetic ones. A well-balanced diet usually satisfies
the minimum vitamin requirements of human beings. The Recommended Dietary
Allowance (RDA) of each vitamin is the standard guideline put forward by the
Food and Nutrition Board, National Academy of Sciences. National Research
Council. It is based on the nutritional needs of an average, healthy person.
Different amounts may be recommended for children, older people, lactating
mothers, or people dealing with an ongoing disease process. The U.S. RDA was
the federal government's interpretation of the National Research
Council's RDA. Since mid-1994, the U.S. RDA has been replaced on food labels by
a Percent Daily Value (the percentage of the U.S. RDA that the labeled food offers). Listings
for vitamins A and C are required; others are optional.
The amount of each
vitamin that should be consumed for optimal health and the wisdom of taking
vitamin supplements, especially in "mega doses," is a controversial
question. The Dietary Supplement
Health and Education Act of 1994 defined vitamins as dietary supplements (rather
than drugs) and shifted the burden of proof of safety from the manufacturers to
the Food and Drug Administration. Although vitamins were previously seen only
as preventives against the various deficiency diseases, more and more studies have
examined additional health benefits of vitamins. Health claims that are unsubstantiated
by scientific study, however, are regarded by many health and nutrition experts
as fraudulent or dangerous, and many physicians now question the need for healthy
persons to take multivitamin supplements, because many foods, such as milk and bread, are
fortified with vitamins.
Vitamins were
originally classified according to their solubility in water or fats, and as
more and more were discovered they were also classified alphabetically. The
fat-soluble vitamins are A, D, E, and K; the B complex and C vitamins are water
soluble. A group of substances that decrease blood capillary fragility, called
the vitamin P group, are no longer considered to be vitamins.
Vitamin A: Vitamin A (retinol), a fat-soluble lipids, a
broad class of organic products found in living systems. Most are insoluble in
water but soluble in non polar solvents. The definition excludes the mineral
oils and other petroleum products obtained from fossil material. Major classes
of lipids include the fatty acids. A is either derived directly from animal
foods such as liver, egg yolks, cream, or butter or is derived from
beta-carotene (kar`ətçn'), long-chained, unsaturated hydrocarbon
found as a pigment in many higher plants, particularly carrots, sweet potatoes,
and leafy vegetables. a pigment that occurs in leafy green vegetables and in
yellow fruits and vegetables. Vitamin A is essential to skeletal growth, normal
reproductive function, and the health of the skin and mucous membranes. One
form, retinal, is a component of visual purple, a photoreceptor pigment in the
retina of the eye vision, physiological sense of sight by which the form,
color, size, movements, and distance of objects are perceived.
Vision in Humans
The human eye
functions somewhat like a camera; that is, it receives and focuses light upon a
photosensitive receiver, the retina. In addition, beta-carotene, like other
carotenoids, is now recognized as an important antioxidant, substance that
prevents or slows the breakdown of another substance by oxygen. Synthetic and
natural antioxidants are used to slow the deterioration of gasoline and rubber,
and such antioxidants as vitamin C (ascorbic acid), butylated hydroxytoluene (BHT),
and butylated hydroxyanisole (BHA) are added to foods to prevent them from becoming
rancid or from discoloring. A deficiency of vitamin A can cause retarded
skeletal growth, night blindness, various abnormalities of the skin and linings
of the genitourinary system and gastrointestinal tract, and, in children,
susceptibility to serious infection. The eye disorders that result from a deficiency
of vitamin A can lead to permanent blindness. Severe deficiency can cause death.
As with the other fat-soluble vitamins, conditions that lead to an inability to
absorb fats, such as obstruction of bile flow or excessive use of mineral oil,
can produce a deficiency state.
Overconsumption of vitamin A can cause irritability, painful joints, growth retardation,
liver and spleen enlargement, hair loss, and birth defects. The National Research
Council recommended daily dietary allowance for adults is 1,000 micrograms (retinol
equivalents) for men and 800 micrograms for women.
Vitamin B
Complex:- Commonly grouped
as the vitamin B complex are eight water-soluble vitamins.
Thiamine: Thiamine (vitamin B1 or anti beriberi factor)
is a necessary ingredient for the biosynthesis of the co enzyme thiamine
pyrophosphate; in this latter form it plays an important role in carbohydrate
metabolism. Good sources are yeast, whole grains, lean pork, nuts, legumes, and
thiamine-enriched cereal products. This vitamin is a factor in the maintenance
of appetite, normal intestinal function, and in the health of the
cardiovascular and nervous systems. A deficiency of the vitamin may lead to
beriberi (bĕr`çbĕr`ç), deficiency disease occurring when the human body has
insufficient amounts of thiamine (vitamin B1). The disease was first shown to
result from a dietary deficiency by Dutch physician Christiaan Eijkman,
Christiaan (krĭs`tyan îk`man),
1858.1930, Dutch physician. He was head of the Pathological Institute of
Batavia and later (1898.1928) professor of hygiene at the Univ. Recommended
dietary allowance for adults is 1.2 to 1.4 mg for men and 1.0 to 1.1 mg for women.
Riboflavin: Riboflavin (vitamin B2 or lactoflavin) is
used to synthesize two co enzymes that are associated with several of the
respiratory enzymes of plants and animals (including humans) and is therefore
important in biochemical oxidation and reductions. Deficiency leads to
fissures in the corners of the mouth, inflammation of the tongue showing a
reddish purple coloration, skin disease, and often severe irritation of the
eyes. The recommended dietary allowance for adults is 1.4 to 1.7 mg for men and
1.2 to 1.3 mg for women. Riboflavin is widely distributed in plant and animal
tissues; milk, organ meats, and enriched cereal products are good sources.
Niacin: The B vitamins niacin (nicotinic acid) and
niacinamide (nicotinamide) are commonly known as preventives of pellagra (pəlãg`rə), deficiency disease due to a lack of niacin (nicotinic acid), one of the
components of the B complex vitamins in the diet. which in 1912 was shown by
American medical researcher Joseph Goldberger to result from a dietary deficiency.
Niacin was first synthesized in 1867. The amino acid tryptophan (trĭp`təfãn), organic compound, one of the 20 amino acids commonly found in animal
proteins. Only the L-stereoisomer appears in mammalian protein. Niacin is the
precursor of niacin. Niacin and niacinamide function in the biochemistry of humans
and other organisms as components of the two co enzymes nicotinamide adenine dinucleotide
(NAD) and nicotinamide adenine dinucleotide phosphate (NADP); these operate in
many enzyme-catalyzed oxidation and reduction reactions. The deficiency state in
humans causes skin disease, diarrhea, dementia, and ultimately death. The
deficiency state in dogs analogous to pellagra in humans is called black tongue
disease. Lean meats, peanuts and other legumes, and whole-grain or enriched
bread and cereal products are among the best sources of niacin. The recommended
daily dietary allowance for adults is 16 to 19 mg niacin equivalents (60 mg of
dietary tryptophan to 1 mg of niacin) for men and 13 to 14 mg for women.
Vitamin B6 Group: Pyridoxine, pyridoxal, and pyridoxamine make
up the vitamin B6 group. They all combine with phosphorus in the body to form
the co enzyme pyridoxal phosphate, which is necessary in the metabolism of amino
acids, glucose, and fatty acids. The best sources of B6 vitamins are liver and
other organ meats, corn, whole-grain cereal, and seeds. Deficiency can result
in central nervous system disturbances (e.g., convulsions in infants) due to
the role of B6 in serotonin (sĕr'ətô`nĭn), organic compound that was
first recognized as a powerful vaso constrictor occurring in blood serum. It was
partially purified, crystallized, and named in 1948, and its structure was
deduced a year later. Gamma-aminobutyric acid synthesis. More generally the
effects of deficiency include inadequate growth
or weight loss and anemia due to the role of B6 in the manufacture of hemoglobin (hç`məglô'bĭn), respiratory protein found in the red blood cells (erythrocytes)
of all vertebrates and some invertebrates. A hemoglobin molecule is composed of
a protein group, known as globin, and four heme groups, each associated with an
iron atom.
The recommended
dietary allowance for adults is 2.0 to 2.2 mg for men and 2 mg for women.
Additional doses are required in pregnancy and by those taking oral
contraceptives or the tuberculosis drug izoniazid. Severe nerve damage has been
reported from mega doses.
Pantothenic Acid: Pantothenic acid, another B vitamin, is
present in perhaps all animal and plant tissues, as well as in many
microorganisms. Good sources of it include liver, kidney, eggs, and dairy products.
It is a component of the important substance co enzyme A, which is involved in the
metabolism of many biochemical substances including fatty acids, steroids, phospholipids,
heme, amino acids, and carbohydrates. The adrenal gland is an important site of
pantothenic acid activity. There is no known naturally occurring deficiency
state and no known toxicity to pantothenic acid.The estimated safe and adequate
daily intake for adults is 4 to 7 mg.
Biotin: Biotin is a B vitamin that functions as a
co enzyme in the metabolism of carbohydrates, fats,and amino acids. Although it
is vitally necessary to the body, only exceedingly small quantities are needed,
and since biotin is synthesized by intestinal bacteria, naturally occurring
biotin deficiency disease is virtually unknown. The disease state can be
produced artificially by including large quantities of raw egg white in the
diet; the whites contain avidin, a biotin antagonist. Especially good sources
of this widely distributed vitamin include egg yolk, kidney, liver, tomatoes,
and yeast. There is no known toxicity to biotin. The estimated safe and
adequate daily intake for adults is 100 to 200 micrograms.
Folic Acid : Folic acid (pteroylglutamic acid, folacin, or
vitamin B9) occurs abundantly in green leafy vegetables, fruits (e.g., apples
and oranges), dried beans, avocados, sunflower seeds, and wheat germ.
Derivatives of this vitamin are directly involved in the synthesis of nucleic acids;
for this reason cells in the body that are subject to rapid synthesis and
destruction are especially sensitive to folic acid deprivation. For example,
the retarded synthesis of blood cells in folic acid deficiency results in
several forms of anemia, while failure to replace rapidly destroyed cells in
the intestinal wall results in a disease called sprue. Inadequate amounts of
folic acid in the diet of pregnant women have been strongly associated with neural
tube defects (i.e., spina bifida and anencephaly) in newborns; fortification of
flours, cornmeal, rice, and pasta (in a manner similar to the fortification of
milk with vitamin D) has been required in the United States since 1998. Adequate
folic acid also reduces the risk of premature birth. A U.S. study
published in 1998 involving 80,000 women showed significant reduction of heart
disease among those whose diets included adequate amounts of folate and vitamin
B6. Several chemical antagonists to the action of folic acid have been developed
in the hope that they might inhibit the growth of rapidly dividing cancer
cells; one such compound, methotrexate, drug used in halting the growth of
actively proliferating tissues. Introduced in the 1950s, it is used in the
treatment of leukemia , psoriasis , and non-Hodgkin's lymphoma . By binding to
an enzyme that controls the metabolism of folic acid, methotrexate interferes
with synthesis of nucleic acids and therefore with tissue cell reproduction.
Folic Acid is used
to treat leukemia (l kç`mçə), cancerous disorder of the blood-forming tissues
(bone marrow), In children. The recommended daily dietary allowance for adults
is 400 micrograms. Paraaminobenzoic acid (PABA), which is incorporated into the
folic acid molecule, is sometimes listed separately as a B vitamin, although
there is no evidence that it is essential to the diet of humans.
Vitamin B12: The molecular structure of vitamin B12
(cobalamin), the most complex of all known vitamins, was announced in 1955 by
several scientists, including British biochemists A. R. Todd and Dorothy
Hodgkin, Dorothy Mary Crowfoot, 1910.94, English chemist and X-ray crystallographer,
b. Egypt.
She received the 1964 Nobel Prize in chemistry for determining the structure of
biochemical compounds (particularly of vitamin B12) used to control pernicious
anemia.
In 1973 the
vitamin was reported to have been synthesized by organic chemists. Vitamin
B12 and closely
related cobalamins are necessary for folic acid to fulfill its role; both are involved
in the synthesis of proteins. American physicians G. R. Minot, George Richards (mî`nət), 1885.1950, American physician and
pathologist, b. Boston,
M.D. Harvard, 1912.
From 1928 to 1948
he was professor of medicine at Harvard and director of the Thorndike
Memorial
Laboratory, Boston
City Hospital.
W. P. Murphy, William Parry, 1892.1987, American physician, b. Stoughton, Wis.,
M.D. Harvard, 1920. He taught at Harvard from 1923 and was associated with the Peter Bent Brigham Hospital,
in Boston, from
1922. He made special studies of diabetes and diseases of the blood and
particularly of the liver treatment for pernicious anemia. in 1926 fed large
amounts of liver to patients with pernicious anemia and cured them; the curative
substance in this case was probably vitamin B12. However, pernicious anemia in humans
is caused not by a vitamin B12 deficiency in the diet but rather the absence of
a substance called the intrinsic factor, ordinarily secreted by the stomach and
responsible for facilitating the absorption of B12 from the intestine. When a
person's body cannot produce the intrinsic factor, the standard treatment today
is to inject vitamin B12 directly into the bloodstream. Minot and Murphy's therapy worked because the
liver they fed their patients contained such large quantities of B12 that
sufficient amounts of the vitamin were absorbed without the assistance of the
intrinsic factor. Inadequate absorption of B12 causes pernicious anemia,
nervous system degeneration, and amenorrhea. The only site of cobalamin
synthesis in nature appears to be in microorganisms; neither animals nor higher
plants are capable of making these vitamin B12 derivatives. Nevertheless, such
animal tissues as the liver, kidney, and heart of ruminants contain relatively
large quantities of vitamin B12; the vitamin stored in these organs was
originally produced by the bacteria in the ruminant gut. Bivalves (clams or
oysters), which siphon microorganisms from the sea, are also good sources.
Plants, on the other hand, are poor sources of vitamin B12. The recommended
daily dietary allowance for adults is 3 micrograms.
Vitamin C: Vitamin C, or ascorbic acid, a water-soluble
vitamin, was first isolated (from adrenal cortex, oranges, cabbage, and lemon
juice) in the laboratories of American biochemists Albert Szent-Gyorgyi, Albert
von (al`bĕrt fən sĕnt'-dyor`dyĭ), 1893.1986, American
biochemist, B.Hungary, M.D. Univ. of Budapest,
1917; Ph. Charles King in the years 1928.33. Szent-Gyorgyi found the Hungarian
red pepper to be an exceptionally rich source; citrus fruits and tomatoes are
also excellent sources. Other good sources include berries, fresh green and
yellow vegetables, and white potatoes and sweet potatoes. The vitamin is
readily oxidized and therefore is easily destroyed in cooking and during
storage. All animals except humans, other primates, guinea pigs, and one bat and
bird species are able to synthesize ascorbic acid. Ascorbic acid is necessary
for the synthesis of the body's cementing substances: bone matrix, collagen (kŏl`əjən), any of a group of proteins found in skin, ligaments, tendons, bone and
cartilage, and other connective tissue Cells called fibroblasts form the
various fibers in connective tissue in the body. Dentin and cartilage. It is an
antioxidant and is necessary to several metabolic processes. Deficiency of
vitamin C results in scurvy, deficiency disorder resulting from a lack of
vitamin C (ascorbic acid) in the diet. Scurvy does not occur in most animals
because they can synthesize their own vitamin C, but humans, other primates,
guinea pigs, and a few other species lack an enzyme necessary for such
synthesis and must obtain vitamin C through their diet. The symptoms of which
are largely related to inadequate collagen synthesis and defective formation of
inter cellular materials. Ascorbic acid is metabolized slowly in humans, and symptoms
of scurvy are usually not seen for three or four months in the absence of any dietary
vitamin C. The use of mega doses of ascorbic acid to prevent common colds,
stress, mental illness, cancer, and heart disease is a continuing subject of
research. The recommended daily allowance for adults is 60 mg.
Vitamin D: Vitamin D is a name given to two fat-soluble
compounds; calciferol (vitamin D2) and cholecalciferol (vitamin D3). They are
now known to be hormones, but continue to be grouped with vitamins because of
historical misclassification. Vitamin D3 plays an essential role in the
metabolism of calcium and phosphorus in the body and prevents rickets or rachitis
(rəkî`tĭs), bone disease caused by a deficiency of vitamin D or calcium.
Essential in regulating in children. A plentiful supply of
7-dehydrocholesterol, the precursor of vitamin D3, exists in human skin and
needs only to be activated by a moderate amount of ultraviolet light (less than
a half hour of sunlight) to become fully potent. Rickets is usually caused by a
lack of exposure to sunlight rather than a dietary deficiency, although dietary
deficiencies can result from mal absorption in the small intestine caused by
conditions such as sprue or colitis. Rickets can be prevented and its course
halted by the intake of vitamin D2 (found in irradiated yeast and used in some
commercial preparations of the vitamin) or vitamin D3 (found in fish liver oils
and in fortified milk). Symptoms of vitamin D deficiency in children include
bowlegs, knock knees, and more severe (often crippling) deformations of the bones.
In adults deficiency results in osteomalacia, characterized by a softening of
the bones. Excessive vitamin D consumption can result in toxicity. Symptoms
include nausea, loss of appetite, kidney damage, and deposits of insoluble
calcium salts in certain tissues. The recommended daily dietary allowance for
cholecalciferol is 5 to 10 micrograms (200 to 400 IU) depending upon age and
the availability of sunlight. Fortified cow's milk supplies 400 IU per quart
(422 IU per liter).
Vitamin E: Vitamin E occurs in at least eight molecular
forms (tocopherols or tocotrienols); in humans the most biologically active
form has generally been considered to be alpha-tocopherol, which is also the
most common. All forms exist as light yellow, viscous oils. The best sources
are vegetable oils. Other sources include green leafy vegetables, wheat germ, some
nuts, and eggs. Vitamin E is necessary for the maintenance of cell membranes.
It is essential to normal reproduction in some animals, but there is no
evidence that it plays a role in human reproduction. It is a potent
antioxidant; numerous studies have pointed to a protective effect against arterial
plaque buildup and cancer. It is helpful in the relief of intermittent
claudication (calf pain) and in preventing problems peculiar to premature
infants. In large doses, it has an anticoagulant effect. The recommended daily
dietary allowance for adults is 10 mg (tocopherol equivalents) for men and 8 mg
for women, but nutritionists and physicians sometimes recommend higher doses for
disease prevention.
Vitamin K: Vitamin K consists of substances that are
essential for the clotting of blood. It was identified in 1934 by Danish
biochemist Henrik Dam, Henrik (hãn`rçk
dam), 1895.1976, Danish biochemist. He identified vitamin K in 1934 and
later investigated the role of vitamin E in nutrition. Two types of K vitamins
have been isolated: K1, an oil purified from alfalfa concentrates, and K2, synthesized by the normal intestinal bacteria. Both
can be derived from the synthetic compound menadione (sometimes called vitamin
K3), a yellow crystalline solid that is as potent in its ability to promote
blood clotting, process by which the blood coagulates to form solid masses, or
clots. In minor injuries, small oval bodies called platelets, or thrombocytes,
tend to collect and form plugs in blood vessel openings. To control bleeding
from vessels larger than capillaries a clot must form at the point of injury. As
the natural vitamins. The best sources are leafy green vegetables, such as
cabbage and spinach, and intestinal bacteria (which produce most of the body's
supply of vitamin K). Vitamin K is required for the synthesis in the liver of
several blood clotting factors, including prothrombin. Coumarin derivatives,
used in medicine to prevent blood coagulation in certain cases, act by
antagonizing the action of vitamin K. In the deficiency state an abnormal
length of time is needed for the blood to clot, and there may be hemorrhaging
in various tissues. Deficiency occurs in hemorrhagic disease of the newborn
infant, in liver damage, and in cases where the vitamin is not absorbed
properly by the intestine. It can also occur in coumarin therapy or when normal
intestinal bacteria are destroyed by extended antibiotic therapy. Vitamin K
does not treat hemophilia. Deficiency is rarely of dietary origin. The
estimated safe and adequate intake for adults is 70 to 140 micrograms.
IRON IN
HUMAN BODY
Do we need
iron for health? :: Iron is essential to
proper nutrition. The metal is
important in many key functions in the human body from the transport of oxygen
in the blood to helpful enzymes in the immune system that help fight infection.
In fact, it was the first trace element identified as a necessary part of the
human diet early in the seventeenth century. The first attempts at producing
dietary iron supplements involved dissolving iron filings in wine as a
treatment for a condition known as chlorosis (an iron deficiency causing a
greenish-yellow discoloration of the skin). Today iron supplements take the
form of vitamin tablets that we take orally. A lack of iron in the diet can
have serious consequences. Iron deficiency anemia is one of the most common
forms of malnutrition in the world today. This disease is characterized by a
low concentration of red blood cells or low levels of hemoglobin, a protein in
red blood cells where 70 percent of the body’s iron is stored. When the body
recognizes that there is not enough stored iron for normal function, it cuts
down on the production of hemoglobin leaving the blood with a lower
oxygen-carrying capacity. This very slowly suffocates tissues. Over time, a
person with iron deficiency anemia might develop symptoms such as fatigue,
dizziness, weakness, irritability, pallor, rapid heartbeat and shortness of
breath. Iron deficiency anemia has been identified in a large percentage of the
world’s population with pregnant women, children, and teens at greatest risk
for developing the disease.
Women of
childbearing age are at particular risk since they regularly lose iron through blood
discharged in menstruation. Still another form of iron deficiency is
sickle-cell anemia, a notorious genetic disorder. This disease is genetically
recessive, meaning that one must have inherited a defective copy of the gene
from both parents to develop the disorder. This disease is caused by an abnormality
in the way hemoglobin proteins form. Instead of the saucer-like shape of normal
red blood cells, these cells are crescent- or sickle-shaped. Sickle-shaped red
blood cells are unable to carry oxygen as well as normal cells, leading to a
condition that causes many of the symptoms of acquired iron deficiency anemia.
However, this disease carries the added risk of blood clots since the
abnormally shaped cells are more likely to stick to each other and the walls of
the blood vessels. Unfortunately, simply increasing the dietary iron intake
will not help individuals with this disease. There is currently no cure, but
there is hope that through persistent research, a cure can be found. Currently,
people with sickle-cell disease can be treated with a host of drugs that alleviate
symptoms and prevent opportunistic infections that arise as a result of a weakened
immune system. A 1999 report in the Journal of the American Medical
Association (JAMA)
described in vitro fertilization techniques can prevent the disease from
being handed down
to offspring.
Can too much
iron harm living things? :: While iron is
essential for health, too much iron can be harmful even deadly. As with iron deficiencies,
there are two conditions that overload the body with iron, one genetic and one acquired.
Both conditions relate to iron in the bloodstream. This time, however, the ill effects have
nothing to with the amount of oxygen reaching organ tissues. Iron overload exerts
its toxic effects through the amount of iron deposited in the liver, heart,
pancreas, joints, and
pituitary gland. Hemochromatosis is
a recessive genetic disorder affecting an estimated one out of every two
hundred individuals of Caucasian descent. One person in ten carries a single
defective gene, and about 1
in 300 carries two copies (they are said to be homozygous for the gene). The proportion
of these people who have disease symptoms is not clear. Hemochromotosis makes
the body prone to absorbing large amounts of iron from the diet, leading to accumulation
of iron deposits in their organs. This iron excess can lead to darkening of the
skin, liver cancer, cirrhosis of the liver, enlargement of the heart,
congestive heart failure, infertility, impotence, joint pains and diabetes. In
most cases, the disease is identified because of symptoms of fatigue, lethargy,
arthritis or impotence. Blood tests and a liver biopsy with quantitative iron
testing are accepted as the best means of confirming the disease. Since the
condition is caused by an excess of iron in the blood, this is one of the few diseases
for which the medieval treatment of draining blood is the most effective
treatment.
This is done
through a medical procedure called therapeutic phlebotomy. Occasionally, people
acquire iron overload. This can result from multiple blood transfusions, for
example as treatment for inherited blood disorders such as thalassemias. Iron
is common in tobacco products, so heavy smokers are at elevated risk for
acquiring iron overload. Welders can also inhale excessive amounts of iron,
though the problem remains confined to the lung. Those who consume large
quantities of red meat and use tobacco products are at increased risk of
developing the condition. An excess of vitamin C in the diet is also known to
promote the absorption of dietary iron. Acquired iron overload in these cases
is generally mild, and can be treated by simply avoiding or reducing the main sources
of iron ingestion. One of the most serious forms of iron overload is acute iron
poisoning. While iron-fortified vitamin tablets may be a convenient way to
round out a diet, they can be harmful to small children and infants if consumed
in high amounts. Acute iron poisoning resulting from overdoses on
iron-fortified vitamin tablets and iron-containing drugs is the leading cause
of poisoning death of children under the age of six in the United States,
according to the United States Food and Drug Administration (FDA). Since 1986,
over 110,000 incidents of iron poisoning resulting from accidental ingestion of
iron tablets by children under the age of six have been reported to poison
control centers. Of those cases, 35 resulted in death. In 1994, the FDA
released guidelines to help curb the tide of iron poisoning cases. New labels
must be stamped on iron-containing drugs and dietary supplements. The message
to consumers reads: "WARNING: Accidental overdose of iron-containing
products is a leading cause of fatal poisoning in children under six. Keep this
product out of reach of children. In case of accidental overdose, call a doctor
or poison control center immediately." The FDA has also
instituted an education campaign to inform parents about the dangers of iron poisoning
in children.
Can iron harm the
environment?
Iron overdoses can
be severe in human beings, especially children, but its effects within ecosystems can be
far more widespread and circuitous. As with humans, iron is essential to most living
organisms. Animals, plants, and even bacteria require the metal for proper
metabolism. However, when human activities alter the geochemistry within an
ecosystem and allow for chemical interactions with iron that would not normally
occur in nature, iron quickly becomes an accomplice in many insidious
environmental problems. Take the mining industry, for example, and a problem
known as acid mine drainage (AMD). When companies mine metals such as copper,
gold, lead, uranium, and zinc, they often seek metal deposits near the earths
crust and dig what are known as open pit mines. Metal ores that have been
sheltered from the earth’s weather for millions of years may suddenly be
exposed to air and rain water. This new mixture of air, water, and heavy metal
compounds makes for a series of new and environmentally harmful chemical
reactions collectively known as AMD. Sulfur and iron are the key components
that allow the reactions to proceed. Heavy metal compounds containing sulfur
can dissolve in the lightly acidic rain water, releasing sulfur into the rain
water runoff. One common waste mineral in the mining industry known as pyrite,
iron disulfide (FeS2), or fool’s gold reacts with the air and water to form
sulfuric acid (H2SO4). This makes for extremely acidic water conditions that
can lower the pH of streams and rivers to levels that are hazardous to aquatic
life. Iron does not simply come along for the ride in the AMD process. Iron can
be a useful tracer for AMD as well as an environmental menace itself. Bright
orange water and rocks in a mine’s effluent stream are a tell-tale sign of AMD.
Ferric hydroxide (Fe(OH)3) or .yellow-boy.
is a bright orange, rusty-colored compound that forms during the series
of reactions that lead to AMD runoff. When yellow-boy begins to cloud the water
near a mine, it is a sign that sulfuric acid is also present. Not only does
.yellow-boy. clearly mark the AMD process, but it can harm aquatic life
directly when if precipitates out of
runoff. As mining runoff moves downstream, chemical reactions in the stream can
act to buffer or neutralize the effluent. However, as the pH of the water
returns to neutral levels, yellow-boy becomes less soluble and precipitates out
of the mixture in bright orange, rusty-colored clouds. The un dissolved
particles can harm the aquatic ecosystem by blocking light and blanketing stream
beds, which obscures food sources for bottom dwellers. AMD is a severe
environmental and economic problem in the United States. It is estimated that
AMD in combination with other toxins from abandoned mines in the U.S. have
polluted 180,000 acres of reservoirs and lakes as well as 12,000 miles of
streams and rivers. The cost to taxpayers of cleaning up this pollution is
estimated to be between $32 and $72 billion. Iron can damage aquatic
communities in more subtle ways. Aquatic organisms such as algae and bacteria
can thrive in iron-rich environments, such as effluent from iron ore mining
plants. When this mineral-rich effluent is pumped into an established and
stable aquatic ecosystem, growth of algae and iron-metabolizing bacteria is
stimulated. Such was the case in 1956 when the Reserve Mining Company opened
shop on Lake Superior’s Silver Bay in Minnesota.
The plant at Silver
Bay was extracting
taconite ore for steel production. The taconite effluent and tailings. The
mineral silt that results from ore processing were procedurally pumped through
a pipe into Lake Superior. The effluent
contained large amounts of iron and other more harmful metals.
