w8pedia:Nutrition:Vitamins

A Vitamin is an organic molecule required by a living organism in minute amounts for proper health. An organism deprived of all sources of a particular vitamin will eventually suffer from disease symptoms specific to that vitamin.

Vitamins can either be classified as water soluble, which means they dissolve easily in water or fat soluble, which means they are absorbed through the intestinal tract with the help of fats.

In general, an organism must obtain vitamins or their metabolic precursors from outside the body, most often from the organism's diet. Examples of vitamins that the human body can derive from precursors include vitamin A, which can be produced from beta carotene; niacin from the amino acid, tryptophan; and vitamin D through exposure of skin to ultraviolet light.

The term, vitamin, does not encompass other essential nutrients such as dietary minerals, essential fatty acids or essential amino acids, nor is it used for the large number of other nutrients that are merely health promoting, but not strictly essential.

The word vitamin was coined by the Polish biochemist Casimir Funk in 1912. Vita in Latin is life and the -amin suffix is short for amine; at the time it was thought that all vitamins were amines. Though this is now known to be incorrect, the name has stuck.

History

The value of eating certain foods to maintain health was recognized long before vitamins were identified. The ancient Egyptians knew that feeding a patient liver would help cure night blindness, now known to be caused by a Vitamin A deficiency. In 1747, the Scottish surgeon James Lind discovered that citrus foods helped prevent scurvy, a particularly deadly disease characterized by bleeding and severe pain. In 1753, Lind published his Treatise on the Scurvy. His discovery, however, was not widely accepted. In the Royal Navy's Arctic expeditions in the 19th century, for example, it was widely believed that scurvy was prevented by good hygiene on board ship, regular exercise, and maintaining the morale of the crew, rather than by a diet of fresh food, so that Navy expeditions continued to be plagued by scurvy. At the time Robert Falcon Scott made his two expeditions to the Antarctic in the early 20th century, the prevailing medical theory was that scurvy was caused by "tainted" canned food.

In 1881, Russian surgeon Nikolai Lunin fed mice upon an artificial mixture of all the separate constituents of milk known at that time, namely the proteins, fats, carbohydrates, and salts. They died, while the mice fed by a milk, developed normally. He made a conclusion that "a natural food such as milk must therefore contain besides these known principal ingredients small quantities of unknown substances essential to life" [1] However, his conclusion was rejected by other researchers who were unable to reproduces his results. One difference was that he used table sugar, while other researches used milk sugar which still contained small amounts of vitamin B.

In 1905, William Fletcher discovered that eating unpolished rice instead of polished helped prevent the disease beriberi. The following year, Frederick Hopkins postulated that foods contained "accessory factors"—in addition to proteins, carbohydrates, fats, etc.—that were necessary to the human body. When Casimir Funk isolated the water-soluble complex of micronutrients whose bioactivity Fletcher had identified, he proposed that it be named "Vitamine". The name soon became synonymous with Hopkins' "accessory factors", and by the time it was shown that not all vitamins were amines, the word was ubiquitous. In 1920, Jack Cecil Drummond proposed that the final "e" be dropped, to deemphasize the "amine" reference, after the discovery that Vitamin C had no amine component, and the name has been "vitamin" ever since.

Throughout the early 1900s, scientists were able to isolate and identify a number of vitamins by depriving animals of them. Initially, lipid from fish oil was used to cure rickets in rats, and the fat-soluble nutrient was called "antirachitic A". The irony here is that the first "vitamin" bioactivity ever isolated, which cured rickets, was initially called vitamine A, this bioactivity is now called vitamin D which is subject to the semantic debate that vitamin D is not truly a vitamin. What we now call "vitamin A" was identified in fish oil because it was inactivated by ultraviolet light. Most of what we now recognize as the water-soluble organic micronutrients were initially referred to as just one entity, "vitamin B".

Human vitamins

In humans, there are thirteen vitamins, divided into two groups, the four fat soluble vitamins (A, D, E and K) and the nine water soluble vitamins (eight B vitamins and vitamin C).

Some of the vitamins are known by other names in older literature. Vitamin B₂ is also referred to as Vitamin G. Vitamin B₇, or Biotin is also referred to as Vitamin H. Vitamin B₉, or Folic Acid is also referred to as Vitamin M. Vitamin B₃ is also referred to as "Vitamin PP", a name derived from the obsolete term "pellagra-preventing factor". Many other essential dietary substances were originally called vitamins and are now classified differently.

Vitamin deficiency and excess

An organism can survive for some time without vitamins, although prolonged vitamin deficit results in a disease state, often painful and potentially deadly. Body stores for different vitamins can vary widely; an adult may be deficient in Vitamins A or B₁₂ for a year or more before developing a deficiency condition, while Vitamin B₁ stores may only last a couple of weeks.

Fat-soluble vitamins may be stored in the body and can cause toxicity when taken in excess. Water-soluble vitamins are not stored in the body, with the exception of Vitamin B₁₂, which is stored in the liver.

Pseudo-vitamins

• Vitamin F was the designation originally given to essential fatty acids that the body cannot manufacture. They were "de-vitaminized" because they are fatty acids. Fatty acids are a major component of fats which, like water, are needed by the body in large quantities and thus do not fit the definition of vitamins which are needed only in trace amounts.
• Although there is no Vitamin S, the suggestion has been made that salicylic acid may qualify for the criteria needed to be defined as a vitamin, and that in this case the designation "Vitamin S" could be used to describe it.
• Herbalists and naturopaths have named various herbs and chemicals "vitamins", even though they are not, including Vitamin T and Vitamin U.
• Some authorities say that Ubiquinone, also called Coenzyme Q₁₀, is a vitamin. Ubiquinone is manufactured in small amounts by the body, like Vitamin D.
• Pangamic acid and the related substance dimethylglycine are sometimes referred to as Vitamin B₁₅.
• Laetrile is sometimes referred to as Vitamin B₁₇. Both pangamic acid and laetrile were first proposed as vitamins by Ernst T. Krebs; neither are recognized by the medical community as vitamins.
• Flavonoids are sometimes called Vitamin P.
• A few substances were once thought to be B-complex vitamins and are referred to as B-vitamins in older literature, including B₄ (Adenine) and B₈, but are no longer recognized as such.

Colloquial usage of the term

• Ativan an antianxiety agent is often called "Vitamin A" (off the record).
• Likewise, Vitamin A and Vitamin C are sometimes used as slang terms for alcoholic beverages and caffeine, respectively.
• Antipsychotic drug haldol is sometimes referred to as Vitamin H in psych hospitals (off-the-record, of course).
• Vitamin I is a colloquialism for ibuprofen.
• Vitamin J has been used to refer to Jägermeister, which is a herbal liquor exported from Germany.
• The sedative Ketamine is often called Vitamin K when used as a recreational drug.
• Vitamin W is a colloquialism for water.
• Vitamin V is a colloquialism for Viagra, Vitamin Z for Zoloft, and Vitamin R for Ritalin, especially when implying that these drugs are overprescribed (or, as a hyperbole, taken as commonly as vitamins).
• Colloquially, the word vitamin is often used to refer to vitamin supplements, products, often in pill form, that contain one or more purified vitamins which are used to supplement the vitamin content of a diet.

Non-human vitamins

Different organisms need different trace organic substances. Most mammals need, with few exceptions, the same vitamins as humans. One notable exception is ascorbic acid; most mammals can synthesize this. The less related a species is to mammals, the more different the organisms' requirements become. For example, some bacteria need adenine. Pyrroloquinoline quinone (PQQ) was reported as a vitamin for mice in 2003. Housecats require the nutrient taurine; this makes it a vitamin for them, but not for humans as they can manufacture their own taurine, although like any internally formed nutrient, taking it directly usually has no harmful effects if done within reason.

References

• STEDMAN'S MEDICAL DICTIONARY. Ed. Maureen Barlow Pugh et.al. 27th ed. Baltimore: Lippincott Williams & Wilkins, 2000.
• Donatelle, Rebecca J. Health: The Basics. 6th ed. San Francisco: Pearson Education, Inc. 2005.
• Funk, C. and H. E. Dubin. The Vitamines. Baltimore: Williams and Wilkins Company, 1922.
• The History of Vitamin Discovery. Retrieved 1 Feb 2005.
• Bellis, Mary. History of Vitamins. Retrieved 1 Feb 2005.
• Challem, Jack (1997). The Past, Present and Future of Vitamins. Retrieved 1 Feb 2005.
• Leonhardt, David (2004). Vitamin A - The Glow in the Dark Vitamin. Retrieved 1 Feb 2005.

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