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Vitamin A
Vitamin B1
Vitamin B2
Vitamin B5
Vitamin B12
Vitamin C
Vitamin D
Vitamin E
Vitamin K
 

 

 

 

 

 

 

 

 

 

 

 A vitamin is an organic compound required as a nutrient in tiny amounts by an organism.A compound is called a vitamin when it cannot be synthesized in sufficient quantities by an organism, and must be obtained from the diet. Thus, the term is conditional both on the circumstances and the particular organism. For example, ascorbic acid functions as Vitamin C for some animals but not others, and Vitamins D and K are required in the human diet only in certain circumstances.

Vitamins are classified by their biological and chemical activity, not their structure. Thus, each "vitamin" may refer to several vitamer compounds that all show the biological activity associated with a particular vitamin. Such a set of chemicals are grouped under an alphabetized vitamin "generic descriptor" title, such as "Vitamin A," which includes the compounds retinal, retinol, and many carotenoids. Vitamers are often inter-convertible in the body. The term vitamin does not include other essential nutrients such as dietary minerals, essential fatty acids, or essential amino acids, nor does it encompass the large number of other nutrients that promote health but are otherwise required less often.

Vitamins have diverse biochemical functions, including function as hormones (e.g. vitamin D), antioxidants (e.g. vitamin E), and mediators of cell signaling and regulators of cell and tissue growth and differentiation (e.g. vitamin A). The largest number of vitamins (e.g. B complex vitamins) function as precursors for enzyme cofactor bio-molecules (coenzymes), that help act as catalysts and substrates in metabolism. When acting as part of a catalyst, vitamins are bound to enzymes and are called prosthetic groups. For example, biotin is part of enzymes involved in making fatty acids. Vitamins also act as coenzymes to carry chemical groups between enzymes. For example, folic acid carries various forms of carbon group methyl, formyl and methylene - in the cell. Although these roles in assisting enzyme reactions are vitamins' best-known function, the other vitamin functions are equally important.

Until the 1900s, vitamins were obtained solely through food intake, and changes in diet (which, for example, could occur during a particular growing season) can alter the types and amounts of vitamins ingested. Vitamins have been produced as commodity chemicals and made widely available as inexpensive pills for several decades, allowing supplementation of the dietary intake.

The Ancient Egyptians knew that feeding a patient liver (back, right) would help cure night blindness.

The value of eating a certain food to maintain health was recognized long before vitamins were identified. The ancient Egyptians knew that feeding a patient liver would help cure night blindness, an illness now known to be caused by a vitamin A deficiency.The advancement of ocean voyage during the Renaissance resulted in prolonged periods without access to fresh fruits and vegetables, and made illnesses from vitamin deficiency common among ship's crew.

In 1749, the Scottish surgeon James Lind discovered that citrus foods helped prevent scurvy, a particularly deadly disease in which collagen is not properly formed, causing poor wound healing, bleeding of the gums, severe pain, and death. In 1753, Lind published his Treatise on the Scurvy, which recommended using lemons and limes to avoid scurvy, which was adopted by the British Royal Navy. This led to the nickname Limey for sailors of that organization. Lind's discovery, however, was not widely accepted by individuals in the Royal Navy's Arctic expeditions in the 19th century, where it was widely believed that scurvy could be prevented by practicing good hygiene, regular exercise, and by maintaining the morale of the crew while on board, rather than by a diet of fresh food. As a result, Arctic expeditions continued to be plagued by scurvy and other deficiency diseases. In the early 20th century, when Robert Falcon Scott made his two expeditions to the Antarctic, the prevailing medical theory was that scurvy was caused by "tainted" canned food.

The discovery of vitamins and their structure

Year of discovery

Vitamin

Source

1909

Vitamin A (Retinol)

Cod liver oil

1912

Vitamin B1 (Thiamin)

Rice bran

1912

Vitamin C (Ascorbic acid)

Lemons

1918

Vitamin D (Calciferol)

Cod liver oil

1920

Vitamin B2 (Riboflavin)

Eggs

1922

Vitamin E (Tocopherol)

Wheat germ oil, Cosmetic and Liver

1926

Vitamin B12 (Cyanocobalamin)

Liver

1929

Vitamin K (Phylloquinone)

Luzerne

1931

Vitamin B5 (Pantothenic acid)

Liver

1931

Vitamin B7 (Biotin)

Liver

1934

Vitamin B6 (Pyridoxine)

Rice bran

1936

Vitamin B3 (Niacin)

Liver

1941

Vitamin B9 (Folic acid)

Liver


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