Vitamins are Organic compound (or a set of closely related molecules called vitamer) that are essential to an organism in small quantities for proper metabolism function. Essential nutrients cannot be biosynthesis in the organism in sufficient quantities for survival, and therefore must be obtained through the diet. For example, vitamin C can be synthesized by some species but not by others; it is not considered a vitamin in the first instance but is in the second. Most vitamins are not single molecules, but groups of related molecules called vitamers. For example, there are eight vitamers of vitamin E: four and four .
The term vitamin does not include the three other groups of essential nutrients: minerals, essential fatty acids, and essential amino acids.
Major health organizations list thirteen vitamins:
Some sources include a fourteenth, choline.
Vitamins have diverse biochemical functions. Vitamin A acts as a regulator of cell and tissue growth and differentiation. Vitamin D provides a hormone-like function, regulating mineral metabolism for bones and other organs. The B complex vitamins function as enzyme cofactors (coenzymes) or the precursors for them. Vitamins C and E function as .
All the vitamins were discovered between 1910 and 1948. Historically, when intake of vitamins from diet was lacking, the results were vitamin deficiency diseases. Then, starting in 1935, commercially produced tablets of yeast-extract vitamin B complex and semi-synthetic vitamin C became available. This was followed in the 1950s by the mass production and marketing of vitamin supplements, including , to prevent vitamin deficiencies in the general population. Governments have mandated the addition of some vitamins to such as flour or milk, referred to as food fortification, to prevent deficiencies. Recommendations for folic acid supplementation during pregnancy reduced risk of infant neural tube defects.
+ The discovery dates of the vitamins and their sources |
Cod liver oil |
Rice bran |
Citrus, most fresh foods |
Cod liver oil |
Meat, dairy products, eggs |
Wheat germ oil, unrefined vegetable oils |
Meat, , in many foods |
Meat, dairy products |
Meat, dairy products, Eggs |
Meat, |
Leaf vegetables |
Meat, organs (Liver), Eggs |
In 1747, the Scotland 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 gingiva, severe pain, and death.Jack Challem (1997). "The Past, Present and Future of Vitamins" In 1753, Lind published his Treatise on the Scurvy, which recommended using and limes to avoid scurvy, which was adopted by the British Royal Navy. This led to the nickname limey for British sailors. However, during the 19th century, limes grown in the West Indies were substituted for lemons; these were subsequently found to be much lower in vitamin C. 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" canning.
In 1881, Russian Empire medical doctor Nikolai Lunin studied the effects of scurvy at the University of Tartu. He fed mice an artificial mixture of all the separate constituents of milk known at that time, namely the , , , 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." However, his conclusions were rejected by his advisor, Gustav von Bunge.
In East Asia, where polished white rice was the common staple food of the middle class, beriberi resulting from lack of vitamin B1 was endemic. In 1884, Takaki Kanehiro, a British-trained medical doctor of the Imperial Japanese Navy, observed that beriberi was endemic among low-ranking crew who often ate nothing but rice, but not among officers who consumed a Western-style diet. With the support of the Japanese navy, he experimented using crews of two ; one crew was fed only white rice, while the other was fed a diet of meat, fish, barley, rice, and beans. The group that ate only white rice documented 161 crew members with beriberi and 25 deaths, while the latter group had only 14 cases of beriberi and no deaths. This convinced Takaki and the Japanese Navy that diet was the cause of beriberi, but they mistakenly believed that sufficient amounts of protein prevented it. That diseases could result from some dietary deficiencies was further investigated by Christiaan Eijkman, who in 1897 discovered that feeding unpolished rice instead of the polished variety to chickens helped to prevent a kind of polyneuritis that was the equivalent of beriberi. The following year, Frederick Hopkins postulated that some foods contained "accessory factors" – in addition to proteins, carbohydrates, fats etc. – that are necessary for the functions of the human body.
The Nobel Prize in Physiology or Medicine for 1929 was awarded to Christiaan Eijkman and Frederick Gowland Hopkins for their contributions to the discovery of vitamins. Thirty-five years earlier, Eijkman had observed that chickens fed polished white rice developed neurological symptoms similar to those observed in military sailors and soldiers fed a rice-based diet, and that the symptoms were reversed when the chickens were switched to whole-grain rice. He called this "the anti-beriberi factor", which was later identified as vitamin B1, thiamine.
In 1930, Paul Karrer elucidated the correct structure for beta-carotene, the main precursor of vitamin A, and identified other carotenoids. Karrer and Norman Haworth confirmed Albert Szent-Györgyi's discovery of ascorbic acid and made significant contributions to the chemistry of flavins, which led to the identification of lactoflavin. For their investigations on carotenoids, flavins and vitamins A and B2, they both received the Nobel Prize in Chemistry in 1937.
In 1931, Albert Szent-Györgyi and a fellow researcher Joseph Svirbely suspected that "hexuronic acid" was actually vitamin C, and gave a sample to Charles Glen King, who proved its ability to counter scurvy in his long-established guinea pig scorbutic assay. In 1937, Szent-Györgyi was awarded the Nobel Prize in Physiology or Medicine for his discovery. In 1943, Edward Adelbert Doisy and Henrik Dam were awarded the Nobel Prize in Physiology or Medicine for their discovery of vitamin K and its chemical structure.
In 1938, Richard Kuhn was awarded the Nobel Prize in Chemistry for his work on carotenoids and vitamins, specifically B2 and B6.
Five people have been awarded for direct and indirect studies of vitamin B12: George Whipple, George Minot and William P. Murphy (1934), Alexander R. Todd (1957), and Dorothy Hodgkin (1964).
In 1967, George Wald, Ragnar Granit and Haldan Keffer Hartline were awarded the Nobel Prize in Physiology and Medicine "...for their discoveries concerning the primary physiological and chemical visual processes in the eye." Wald's contribution was discovering the role vitamin A had in the process.
Robert W. Yoder is credited with first using the term vitamania, in 1942, to describe the appeal of relying on nutritional supplements rather than on obtaining vitamins from a varied diet of foods. The continuing preoccupation with a healthy lifestyle led to an obsessive consumption of vitamins and multi-vitamins, the beneficial effects of which are questionable. As one example, in the 1950s, the Wonder Bread company sponsored the Howdy Doody television show, with host Buffalo Bob Smith telling the audience, "Wonder Bread builds strong bodies 8 ways", referring to the number of Food additive.
Deficiencies of vitamins are classified as either primary or secondary. A primary deficiency occurs when an organism does not get enough of the vitamin in its food. A secondary deficiency may be due to an underlying disorder that prevents or limits the absorption or use of the vitamin, due to a "lifestyle factor", such as smoking, excessive alcohol consumption, or the use of medications that interfere with the absorption or use of the vitamin. People who eat a varied diet are unlikely to develop a severe primary vitamin deficiency, but may be consuming less than the recommended amounts; a national food and supplement survey conducted in the US over 2003–2006 reported that over 90% of individuals who did not consume vitamin supplements were found to have inadequate levels of some of the essential vitamins, notably vitamins D and E.
Well-researched human vitamin deficiencies involve thiamine (beriberi), niacin (pellagra), vitamin C (scurvy), folate (neural tube defects) and vitamin D (rickets). In much of the developed world these deficiencies are rare due to an adequate supply of food and the addition of vitamins to common foods. In addition to these classical vitamin deficiency diseases, some evidence has also suggested links between vitamin deficiency and a number of different disorders.
All values are consumption per day:
EAR US Estimated Average Requirements.
RDA US Recommended Dietary Allowances; higher for adults than for children, and may be even higher for women who are pregnant or lactating.
AI US and EFSA Adequate Intake; AIs established when there is not sufficient information to set EARs and RDAs.
PRI Population Reference Intake is European Union equivalent of RDA; higher for adults than for children, and may be even higher for women who are pregnant or lactating. For Thiamin and Niacin the PRIs are expressed as amounts per MJ of calories consumed. MJ = megajoule = 239 food calories.
UL or Upper Limit Tolerable upper intake levels.
ND ULs have not been determined.
NE EARs have not been established.
Europe has regulations that define limits of vitamin (and mineral) dosages for their safe use as dietary supplements. Most vitamins that are sold as dietary supplements are not supposed to exceed a maximum daily dosage referred to as the tolerable upper intake level (UL or Upper Limit). Vitamin products above these regulatory limits are not considered supplements and should be registered as prescription or non-prescription (over-the-counter drugs) due to their potential side effects. The European Union, United States and Japan establish ULs.
Dietary supplements often contain vitamins, but may also include other ingredients, such as minerals, herbs, and botanicals. Scientific evidence supports the benefits of dietary supplements for persons with certain health conditions. Use and Safety of Dietary Supplements NIH office of Dietary Supplements. In some cases, vitamin supplements may have unwanted effects, especially if taken before surgery, with other dietary supplements or medicines, or if the person taking them has certain health conditions. They may also contain levels of vitamins many times higher, and in different forms, than one may ingest through food.
In 2007, the US Code of Federal Regulations (CFR) Title 21, part III took effect, regulating Good Manufacturing Practices (GMPs) in the manufacturing, packaging, labeling, or holding operations for dietary supplements. Even though product registration is not required, these regulations mandate production and quality control standards (including testing for identity, purity and adulterations) for dietary supplements.U.S. Food and Drug Administration. CFR – Code of Federal Regulations Title 21. Retrieved 16 February 2014. In the European Union, the Food Supplements Directive requires that only those supplements that have been proven safe can be sold without a prescription. For most vitamins, pharmacopoeia have been established. In the United States, the United States Pharmacopeia (USP) sets standards for the most commonly used vitamins and preparations thereof. Likewise, monographs of the European Pharmacopoeia (Ph.Eur.) regulate aspects of identity and purity for vitamins on the European market.
The reason that the set of vitamins skips 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 Danish-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 coagulation of blood following wounding (from the Danish language word Koagulation). At the time, most (but not all) of the letters from F through to J were already designated, so the use of the letter K was considered quite reasonable. The table Nomenclature of reclassified vitamins 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.
The missing numbered B vitamins were reclassified or determined not to be vitamins. For example, B9 is folic acid and five of the folates are in the range B11 through B16. Others, such as PABA (formerly B10), are biologically inactive, toxic, or with unclassifiable effects in humans, or not generally recognised as vitamins by science, Vitamins: What Vitamins Do I Need?. Medical News Today. Retrieved on 30 November 2015. such as the highest-numbered, which some naturopath practitioners call B21 and B22. There are also lettered B substances (e.g., Bm) listed at B vitamins that are not recognized as vitamins. There are other "D vitamins" now recognised as other substances, which some sources of the same type number up to D7. The controversial cancer treatment laetrile was at one point lettered as vitamin B17. There appears to be no consensus on the existence of substances that may have at one time been named as vitamins Q, R, T, V, W, X, Y or Z.
"Vitamin N" is a term popularized for the mental health benefits of spending time in nature settings. "Vitamin I" is slang among athletes for frequent/daily consumption of ibuprofen as a pain-relieving treatment.
"Vitamine" to vitamin
Nobel Prizes for vitamin research
History of promotional marketing
Etymology
Classification
Anti-vitamins
Biochemical functions
On fetal growth and childhood development
On adult health maintenance
Intake
Sources
Deficient intake
Excess intake
Effects of cooking
Vitamin A no partially partially relatively stable Vitamin C very unstable yes no no Vitamin D no no no no Vitamin E no yes yes no Vitamin K no no yes no Thiamine (B1) highly no ? > 100 °C Riboflavin (B2) slightly no in solution no Niacin (B3) yes no no no Pantothenic Acid (B5) quite stable no no yes Vitamin B6 yes ? yes < 160 °C Biotin (B7) somewhat ? ? no Folic Acid (B9) yes ? when dry at high temp Cobalamin (B12) yes ? yes no
Recommended levels
μg mg μg μg mg mg mg mg mg mg μg μg μg
Supplementation
Governmental regulation
Naming
+Nomenclature of reclassified vitamins Vitamin B4 Adenine DNA metabolite; synthesized in body Vitamin B8 Adenylic acid DNA metabolite; synthesized in body Vitamin BT Carnitine Synthesized in body Vitamin F Essential fatty acids Needed in large quantities (does
not fit the definition of a vitamin).Vitamin G Riboflavin Reclassified as B vitamins Vitamin H Biotin Reclassified as B vitamins Vitamin J Catechol, Flavin group Catechol nonessential; flavin reclassified
as B vitaminsVitamin L1Davidson, Michael W. (2004) Anthranilic Acid (Vitamin L) Florida State University. Retrieved 20-02-07. Anthranilic acid Nonessential Vitamin L2 5′-Methylthioadenosine RNA metabolite; synthesized in body Vitamin M or Bc Folate Reclassified as B vitamins Vitamin P Flavonoids Many compounds, not proven essential Vitamin PP Niacin Reclassified as B vitamins Vitamin S Salicylic acid Nonessential Vitamin U S-Methylmethionine Protein metabolite; synthesized in body
See also
Notes
External links
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