Vitamins

Vitamins are organic components in food that are needed in very small amountsfor 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 thewater-soluble vitamins. Vitamins are required in the diet in only tiny amounts, in contrast to the energy components of the diet. The energy components ofthe diet are sugars, starches, fats, and oils, and these occur in relativelylarge 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 causesnight blindness. Severe vitamin A deficiency can result in xerophthalamia, adisease which, if left untreated, results in total blindness. Vitamin K deficiency results in spontaneous bleeding. Mild or moderate folate deficiency iscommon 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 cellscalled 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. Thiamindeficiency results in beriberi, a disease resulting in atrophy, weakness ofthe legs, nerve damage, and heart failure. Vitamin C deficiency results in scurvy, a disease that involves bleeding. Specific diseases uniquely associatedwith deficiencies in vitamin B6, riboflavin, or pantothenic acidhave not been found in the humans, though persons who have been starving, orconsuming poor diets for several months, might be expected to be deficient inmost 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.

People are treated with vitamins for three reasons. The primary reason is torelieve 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.

A third reason for vitamin treatment is to reduce the risk for diseases thatmay occur even when vitamin deficiency cannot be detected by chemical tests.One example is folate deficiency. The risk for cardiovascular disease can beslightly 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 ofthe 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.

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.

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. Forexample, a vegetarian who will not consume meat may be encouraged to consumeoral 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 10-1000 times greater than the RDA. Pernicious anemia, homocystinuria, and biotinidase deficiency are three examples of genetic diseases which are treated with megadoses of vitamins.

Few risks are associated with vitamin treatment. Any possible risks depend onthe 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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