Vitamins
Definition
Vitamins are organic components in food that are needed in very small
amounts for growth and for maintaining good health. The vitamins include vitamin
D, vitamin E, vitamin A, and vitamin K, or the fat-soluble vitamins, and folate
(folic acid), vitamin B12, biotin, vitamin B6, niacin,
thiamin, riboflavin, pantothenic acid, and vitamin C (ascorbic acid), or the
water-soluble vitamins. Vitamins are required in the diet in only tiny amounts,
in contrast to the energy components of the diet. The energy components of the
diet are sugars, starches, fats, and oils, and these occur in relatively large
amounts in the diet.
Most of the vitamins are closely associated with a corresponding
vitamin deficiency disease. Vitamin D deficiency causes rickets, a disease of
the bones. Vitamin E deficiency occurs only very rarely, and causes nerve
damage. Vitamin A deficiency is common throughout the poorer parts of the world,
and causes night blindness. Severe vitamin A deficiency can result in
xerophthalamia, a disease which, if left untreated, results in total blindness.
Vitamin K deficiency results in spontaneous bleeding. Mild or moderate folate
deficiency is common throughout the world, and can result from the failure to
eat green, leafy vegetables or fruits and fruit juices. Folate deficiency causes
megaloblastic anemia, which is characterized by the presence of large abnormal
cells called megaloblasts in the circulating blood. The symptoms of
megaloblastic anemia are tiredness and weakness. Vitamin B12
deficiency occurs with the failure to consume meat, milk or other dairy
products. Vitamin B12 deficiency causes megaloblastic anemia and, if
severe enough, can result in irreversible nerve damage. Niacin deficiency
results in pellagra. Pellagra involves skin rashes and scabs, diarrhea, and
mental depression. Thiamin deficiency results in beriberi, a disease resulting
in atrophy, weakness of the legs, nerve damage, and heart failure. Vitamin C
deficiency results in scurvy, a disease that involves bleeding. Specific
diseases uniquely associated with deficiencies in vitamin B6,
riboflavin, or pantothenic acid have not been found in the humans, though
persons who have been starving, or consuming poor diets for several months,
might be expected to be deficient in most of the nutrients, including vitamin B6,
riboflavin, and pantothenic acid.
Some of the
vitamins serve only one function in the body, while other vitamins serve a
variety of unrelated functions. Hence, some vitamin deficiencies tend to result
in one type of defect, while other deficiencies result in a variety of problems.
Purpose
People are
treated with vitamins for three reasons. The primary reason is to relieve a
vitamin deficiency, when one has been detected. Chemical tests suitable for the
detection of all vitamin deficiencies are available. The diagnosis of vitamin
deficiency is often aided by visual tests, such as the examination of blood
cells with a microscope, the x ray examination of bones, or a visual examination
of the eyes or skin.
A second reason
for vitamin treatment is to prevent the development of an expected deficiency.
Here, vitamins are administered even with no test for possible deficiency. One
example is vitamin K treatment of newborn infants to prevent bleeding. Food
supplementation is another form of vitamin treatment. The vitamin D added to
foods serves the purpose of preventing the deficiency from occurring in persons
who may not be exposed much to sunlight and who fail to consume foods that are
fortified with vitamin D, such as milk. Niacin supplementation prevents
pellagra, a disease that occurs in people who rely heavily on corn as the main
source of food, and who do not eat much meat or milk. In general, the American
food supply is fortified with niacin.
A third reason for vitamin treatment is to reduce the risk for
diseases that may occur even when vitamin deficiency cannot be detected by
chemical tests. One example is folate deficiency. The risk for cardiovascular
disease can be slightly reduced for a large fraction of the population by folic
acid supplements. And the risk for certain birth defects can be sharply reduced
in certain women by folic acid supplements.
Vitamin treatment is important during specific diseases where the
body's normal processing of a vitamin is impaired. In these cases, high doses of
the needed vitamin can force the body to process or utilize it in the normal
manner. One example is pernicious anemia, a disease that tends to occur in
middle age or old age, and impairs the absorption of vitamin B12.
Surveys have revealed that about 0.1% of the general population, and 2-3% of the
elderly, may have the disease. If left untreated, pernicous anemia leads to
nervous system damage. The disease can easily be treated with large oral daily
doses of vitamin B12 (hydroxocobalamin) or with monthly injections of
the vitamin.
Vitamin supplements are widely available as over-the-counter
products. But whether they work to prevent or curtail certain illnesses,
particularly in people with a balanced diet, is a matter of debate and ongoing
research. For example, vitamin C is not proven to prevent the common cold. Yet,
millions of people take it for that reason. Ask a physician or pharmacist for
more information on the appropriate use of multivitamin supplements.
Precautions
Vitamin A and vitamin D can be toxic in high doses. Side effects
range from dizziness to kidney failure. Ask a physician or pharmacist about the
correct use of a multivitamin supplement that contains these vitamins.
Description
Vitamin
treatment is usually done in three ways: by replacing a poor diet with one that
supplies the recommended dietary allowance, by consuming oral supplements, or by
injections. Injections are useful for persons with diseases that prevent
absorption of fat-soluble vitamins. Oral vitamin supplements are especially
useful for persons who otherwise cannot or will not consume food that is a good
vitamin source, such as meat, milk or other dairy products. For example, a
vegetarian who will not consume meat may be encouraged to consume oral
supplements of vitamin B12.
Treatment of
genetic diseases which impair the absorption or utilization of specific vitamins
may require megadoses of the vitamin throughout one's lifetime. Megadose means a
level of about 10-1,000 times greater than the RDA. Pernicious anemia,
homocystinuria, and biotinidase deficiency are three examples of genetic
diseases which are treated with megadoses of vitamins.
Preparation
The diagnosis of
a vitamin deficiency usually involves a blood test. An overnight fast is usually
recommended as preparation prior to withdrawal of the blood test so that
vitamin-fortified foods do not affect the test results.
Aftercare
The response to
vitamin treatment can be monitored by chemical tests, by an examination of red
blood cells or white blood cells, or by physiological tests, depending on the
exact vitamin deficiency.
Risks
Few risks are
associated with vitamin treatment. Any possible risks depend on the vitamin and
the reason why it was prescribed. Ask a physician or pharmacist about how and
when to take vitamin supplements, particularly those that have not been
prescribed by a physician.
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Essential VitaminsVitaminWhat
It Does For The Body Vitamin A (Beta Carotene)Promotes growth and repair
of body tissues; reduces susceptibility to infections; aids in bone and
teeth formation; maintains smooth skinVitamin B-1 (Thiamin)Promotes growth
and muscle tone; aids in the proper functioning of the muscles, heart, and
nervous system; assists in digestion of carbohydratesVitamin B-2 (Riboflavin)Maintains
good vision and healthy skin, hair, and nails; assists in formation of
antibodies and red blood cells; aids in carbohydrate, fat, and protein
metabolismVitamin B-3 (Niacinamide)Reduces cholesterol levels in the
blood; maintains healthy skin, tongue, and digestive system; improves
blood circulation; increases energyVitamin B-5Fortifies white blood cells;
helps the body's resistance to stress; builds cellsVitamin B-6 (Pyridoxine)Aids
in the synthesis and breakdown of amino acids and the metabolism of fats
and carbohydrates; supports the central nervous system; maintains healthy
skinVitamin B-12 (Cobalamin)Promotes growth in children; prevents anemia
by regenerating red blood cells; aids in the metabolism of carbohydrates,
fats, and proteins; maintains healthy nervous systemBiotinAids in the
metabolism of proteins and fats; promotes healthy skinCholineHelps the
liver eliminate toxinsFolic Acid (Folate, Folacin)Promotes the growth and
reproduction of body cells; aids in the formation of red blood cells and
bone marrowVitamin C (Ascorbic Acid)One of the major antioxidants;
essential for healthy teeth, gums, and bones; helps to heal wounds,
fractures, and scar tissue; builds resistance to infections; assists in
the prevention and treatment of the common cold; prevents scurvyVitamin
DImproves the absorption of calcium and phosphorous (essential in the
formation of healthy bones and teeth) maintains nervous systemVitamin EA
major antioxidant; supplies oxygen to blood; provides nourishment to
cells; prevents blood clots; slows cellular agingVitamin K (Menadione)Prevents
internal bleeding; reduces heavy menstrual flow |
Key Terms
Genetic disease
A genetic disease is a disease that
is passed from one generation to the next, but does not necessarily appear in
each generation. An example of genetic disease is Down's syndrome.
Plasma
Blood consists of red and white
cells, as well as other components, that float in a liquid. This liquid is
called plasma.
Recommended dietary allowance (RDA)
The Recommended Dietary Allowances
(RDAs) are quantities of nutrients of the diet that are required to maintain
human health. RDAs are established by the Food and Nutrition Board of the
National Academy of Sciences and may be revised every few years. A separate RDA
value exists for each nutrient. The RDA values refer to the amount of nutrient
expected to maintain health in the greatest number of people.
Serum
Serum is blood plasma with the
blood clotting proteins removed. Serum is prepared by removing blood from the
subject, allowing the blood naturally to form a blood clot, and then using a
centrifuge to remove the red blood cells and the blood clot. The blood clot
takes the form of an indistinct clump.
Vitamin status
Vitamin status refers to the state
of vitamin sufficiency or deficiency of any person. For example, a test may
reveal that a patient's folate status is sufficient, borderline, or severely
inadequate.
