- Plural of vitamin
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" actually refers to a number of vitamer compounds, which form a set of distinct chemical compounds that show the biological activity of a particular vitamin. Such a set of chemicals are grouped under an alphabetized vitamin "generic descriptor" title, such as "vitamin A," which (for example) includes 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 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. 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. He fed mice an artificial mixture of all the separate constituents of milk known at that time, namely the proteins, fats, carbohydrates, and salts. The mice that received only the individual constituents died, while the mice fed by milk itself 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." When the article was translated into German, the translation failed to state that it was a newly discovered nutrient, a claim made in the original Japanese article, and hence his discovery failed to gain publicity. Polish biochemist Kazimierz Funk isolated the same complex of micronutrients and proposed the complex be named "Vitamine" (a portmanteau of "vital amine") in 1912. 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 already 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.
Throughout the early 1900s, the use of deprivation studies allowed scientists to isolate and identify a number of vitamins. 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 "vitamin A", the bioactivity of which is now called vitamin D. What we now call "vitamin A" was identified in fish oil because it was inactivated by ultraviolet light. In 1931, Albert Szent-Györgyi and a fellow researcher Joseph Svirbely determined that "hexuronic acid" was actually vitamin C and noted its anti-scorbutic activity. In 1937, Szent-Györgyi was awarded the Nobel Prize for his discovery. In 1943 Edward Adelbert Doisy and Henrik Dam were awarded the Nobel Prize for their discovery of vitamin K and its chemical structure.
In humansVitamins are classified as either water-soluble, meaning that they dissolve easily in water, or fat-soluble vitamins, which are absorbed through the intestinal tract with the help of lipids (fats). In general, water-soluble vitamins are readily excreted from the body. Each vitamin is typically used in multiple reactions and, therefore, most have multiple functions.
In humans there are 13 vitamins: 4 fat-soluble (A, D, E and K) and 9 water-soluble (8 B vitamins and vitamin C).
In nutrition and diseasesVitamins are essential for the normal growth and development of a multicellular organism. Using the genetic blueprint inherited from its parents, a fetus begins to develop, at the moment of conception, from the nutrients it absorbs. It requires certain vitamins and minerals to be present at certain times. These nutrients facilitate the chemical reactions that produce among other things, skin, bone, and muscle. If there is serious deficiency in one or more of these nutrients, a child may develop a deficiency disease. Even minor deficiencies may cause permanent damage. For the most part, vitamins are obtained with food, but a few are obtained by other means. For example, microorganisms in the intestine—commonly known as "gut flora"—produce vitamin K and biotin, while one form of vitamin D is synthesized in the skin with the help of natural ultraviolet in sunlight. Humans can produce some vitamins from precursors they consume. Examples include vitamin A, produced from beta carotene, and niacin, from the amino acid tryptophan.
Side effects and overdoseIn large doses, some vitamins have documented side effects that tend to be more severe with a larger dosage. The likelihood of consuming too much of any vitamin from food is remote, but overdosing from vitamin supplementation does occur. At high enough dosages some vitamins cause side effects such as nausea, diarrhea, and vomiting,
When side effects emerge, recovery is often accomplished by reducing the dosage. The concentrations of vitamins an individual can tolerate vary widely, and appear to be related to age and state of health. In the United States, overdose exposure to all formulations of vitamins was reported by 62,562 individuals in 2004 (nearly 80% of these exposures were in children under the age of 6), leading to 53 "major" life-threatening outcomes and 3 deaths—a small number in comparison to the 19,250 people who died of unintentional poisoning of all kinds in the U.S. in the same year (2004).
SupplementsDietary supplements, often containing vitamins, are used to ensure that adequate amounts of nutrients are obtained on a daily basis, if optimal amounts of the nutrients cannot be obtained through a varied diet. Scientific evidence supporting the benefits of some dietary supplements is well established for certain health conditions, but others need further study. Some research has suggested that supplements do not only provide no tangible health benefits for generally healthy individuals, but may actually increase mortality.
In the United States, advertising for dietary supplements is required to include a disclaimer that the product is not intended to treat, diagnose, mitigate, prevent, or cure disease, and that any health claims have not been evaluated by the Food and Drug Administration.
Intake of excessive quantities can cause vitamin poisoning, often due to overdose of Vitamin A and Vitamin D (The most common poisoning with multinutrient supplement pills does not involve a vitamin, but is rather due to the mineral iron). Due to toxicity, most common vitamins have recommended upper daily intake amounts.
Governmental regulation of vitamin supplementsMost countries place dietary supplements in a special category under the general umbrella of foods, not drugs. This necessitates that the manufacturer, and not the government, be responsible for ensuring that its dietary supplement products are safe before they are marketed. Unlike drug products, that must explicitly be proven safe and effective for their intended use before marketing, there are often no provisions to "approve" dietary supplements for safety or effectiveness before they reach the consumer. Also unlike drug products, manufacturers and distributors of dietary supplements are not generally required to report any claims of injuries or illnesses that may be related to the use of their products.
Names in current and previous nomenclaturesThe reason the set of vitamins seems to skip directly from E to K is that the vitamins corresponding to "letters" F-J were either reclassified over time, discarded as false leads, or renamed because of their relationship to "vitamin B", which became a "complex" of vitamins. The German-speaking scientists who isolated and described vitamin K (in addition to naming it as such) did so because the vitamin is intimately involved in the Koagulation of blood following wounding. At the time, most (but not all) of the letters from F through J were already designated, so the use of the letter K was considered quite reasonable.
The following table lists chemicals that had previously been classified as vitamins, as well as the earlier names of vitamins that later became part of the B-complex:
See alsoportal Food
- Dietary supplement
- Fat soluble vitamins
- Health freedom movement
- Illnesses related to poor nutrition
- Megavitamin therapy
- Orthomolecular medicine
- Vitamin poisoning (overdose)
- Whole food supplements
ReferencesGeneral References Include:
- 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.
vitamins in Arabic: فيتامين
vitamins in Min Nan: Bî-tá-mín
vitamins in Bosnian: Vitamini
vitamins in Bulgarian: Витамин
vitamins in Catalan: Vitamina
vitamins in Czech: Vitamín
vitamins in Danish: Vitamin
vitamins in German: Vitamine
vitamins in Estonian: Vitamiinid
vitamins in Modern Greek (1453-): Βιταμίνη
vitamins in Spanish: Vitamina
vitamins in Esperanto: Vitamino
vitamins in Basque: Bitamina
vitamins in Persian: ویتامین
vitamins in Faroese: Vitamin
vitamins in French: Vitamine
vitamins in Galician: Vitamina
vitamins in Korean: 비타민
vitamins in Armenian: Վիտամին
vitamins in Croatian: Vitamini
vitamins in Indonesian: Vitamin
vitamins in Icelandic: Vítamín
vitamins in Italian: Vitamine
vitamins in Hebrew: ויטמין
vitamins in Georgian: ვიტამინები
vitamins in Latvian: Vitamīni
vitamins in Luxembourgish: Vitamin
vitamins in Lithuanian: Vitaminas
vitamins in Hungarian: Vitamin
vitamins in Macedonian: Витамин
vitamins in Malayalam: ജീവകം
vitamins in Marathi: जीवनसत्त्व
vitamins in Dutch: Vitamine
vitamins in Japanese: ビタミン
vitamins in Norwegian: Vitamin
vitamins in Norwegian Nynorsk: Vitamin
vitamins in Novial: Vitamine
vitamins in Occitan (post 1500): Vitamina
vitamins in Polish: Witaminy
vitamins in Portuguese: Vitamina
vitamins in Romanian: Vitamină
vitamins in Russian: Витамины
vitamins in Simple English: Vitamin
vitamins in Slovak: Vitamín
vitamins in Slovenian: Vitamin
vitamins in Serbian: Vitamini
vitamins in Sundanese: Vitamin
vitamins in Finnish: Vitamiini
vitamins in Swedish: Vitaminer
vitamins in Tamil: உயிர்ச்சத்து
vitamins in Telugu: విటమిన్
vitamins in Thai: วิตามิน
vitamins in Vietnamese: Vitamin
vitamins in Turkish: Vitamin
vitamins in Ukrainian: Вітаміни
vitamins in Urdu: حیاتین
vitamins in Yiddish: וויטאמין
vitamins in Chinese: 维生素