A vitamin is an organic compound An organic compound is any member of a large class of chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of compounds such as carbonates, simple oxides of carbon and cyanides, as well as the allotropes of carbon, are considered inorganic. The distinction between "organic" and " required as a nutrient A nutrient is a chemical that an organism needs to live and grow or a substance used in an organism's metabolism which must be taken in from its environment. Nutrients are the substances that enrich the body. They build and repair tissues, give heat and energy, and regulate body processes. Methods for nutrient intake vary, with animals and in tiny amounts by an organism In biology, an organism is any contiguous living system . In at least some form, all organisms are capable of response to stimuli, reproduction, growth and development, and maintenance of homoeostasis as a stable whole. An organism may either be unicellular (single-celled) or be composed of, as in humans, many trillions of cells grouped into.^[1] In other words, an organic chemical compound (or related set of compounds) is called a vitamin when it cannot be synthesized Biosynthesis is an enzyme-catalyzed process in cells of living organisms by which substrates are converted to more complex products. The biosynthesis process often consists of several enzymatic steps in which the product of one step is used as substrate in the following step. Examples for such multi-step biosynthetic pathways are those for the 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 Ascorbic acid is a sugar acid with antioxidant properties. Its appearance is white to light-yellow crystals or powder, and it is water-soluble. One form of ascorbic acid is commonly known as vitamin C. The name is derived from a- and scorbutus (scurvy), the disease caused by a deficiency of vitamin C. In 1937 the Nobel Prize for chemistry was (vitamin C Vitamin C or L-ascorbic acid or L-ascorbate is an essential nutrient for humans and certain other animal species, in which it functions as a vitamin. In living organisms, ascorbate is an anti-oxidant, since it protects the body against oxidative stress. It is also a cofactor in at least eight enzymatic reactions, including several collagen) is a vitamin for humans, but not for most other animals, and biotin Biotin is a water-soluble B-complex vitamin that is composed of an ureido (tetrahydroimidizalone) ring fused with a tetrahydrothiophene ring. A valeric acid substituent is attached to one of the carbon atoms of the tetrahydrothiophene ring. Biotin is a coenzyme in the metabolism of fatty acids and leucine, and it plays a role in gluconeogenesis and vitamin D Vitamin D is a group of fat-soluble secosteroids, the two major physiologically relevant forms of which are vitamin D2 and vitamin D3 (cholecalciferol). Vitamin D without a subscript refers to either D2 or D3 or both. Vitamin D3 is produced in the skin of vertebrates after exposure to ultraviolet B light from the sun or artificial sources, and are required in the human diet only in certain circumstances. By convention, the term vitamin does not include other essential nutrients An essential nutrient is a nutrient required for normal body functioning that either cannot be synthesized by the body at all, or cannot be synthesized in amounts adequate for good health , and thus must be obtained from a dietary source. Essential nutrients are also defined by the collective physiological evidence for their importance in the diet, such as dietary minerals Dietary minerals are the chemical elements required by living organisms, other than the four elements carbon, hydrogen, nitrogen, and oxygen present in common organic molecules. The term "mineral" is archaic, since the intent of the definition is to describe ions , not chemical compounds or actual minerals. Examples include calcium, (which are inorganic), essential fatty acids Essential fatty acids, or EFAs, are fatty acids that humans and other animals must ingest for good health because the body requires them but can't make them from other food components. The term refers to fatty acids required for biological processes, and not those that only act as fuel or essential amino acids An essential amino acid or indispensable amino acid is an amino acid that cannot be synthesized de novo by the organism , and therefore must be supplied in the diet (which are needed in larger amounts than vitamins), nor does it encompass the large number of other nutrients that promote health, but are otherwise required less often.^[2] Thirteen vitamins are presently universally recognized.

Vitamins are classified by their biological and chemical activity, not their structure. Thus, each "vitamin" refers to a number of vitamer A vitamer of a particular vitamin is any of the chemical compounds which exhibit vitamin activity. Very commonly "vitamins" are not single compounds, but rather each vitamin, which is defined by its biological activity, not its structure, is actually represented by a number of substances, each of which shows vitamin activity. These 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 Vitamin A is a vitamin that is needed by the retina of the eye in the form of a specific metabolite, the light-absorbing molecule retinal. This molecule is absolutely necessary for both scotopic and color vision. In another version the vitamin is necessary for the function of the reproductive systems of both male and female mammals. Vitamin A also", which includes the compounds retinal Retinal, also called retinaldehyde or vitamin A aldehyde, is one of the many forms of vitamin A . Retinal is a polyene chromophore, and bound to proteins called opsins, is the chemical basis of animal vision. Bound to proteins called type 1 rhodopsins, retinal allows certain microorganisms to convert light into metabolic energy, retinol Retinol, is one of the animal forms of vitamin A. It is a diterpenoid and an alcohol. It is convertable to other forms of vitamin A, but as retinol it is thought to serve an irreplaceable vitamin function in the reproductive tracts of male and female mammals. The retinyl ester derivative of the alcohol serves as the storage form of the vitamin in, and four known carotenoids Carotenoids are tetraterpenoid organic pigments that are naturally occurring in the chloroplasts and chromoplasts of plants and some other photosynthetic organisms like algae, some types of fungus some bacteria and at least one species of aphid. Carotenoids are generally not manufactured by species in the animal kingdom, although one species of. Vitamers by definition are convertible to the active form of the vitamin in the body, and are sometimes inter-convertible to one another, as well.

Vitamins have diverse biochemical functions. Some have hormone-like functions as regulators of mineral metabolism (e.g. vitamin D), or regulators of cell and tissue growth and differentiation (e.g. some forms of vitamin A Vitamin A is a vitamin that is needed by the retina of the eye in the form of a specific metabolite, the light-absorbing molecule retinal. This molecule is absolutely necessary for both scotopic and color vision. In another version the vitamin is necessary for the function of the reproductive systems of both male and female mammals. Vitamin A also). Others function as antioxidants An antioxidant is a molecule capable of inhibiting the oxidation of other molecules. Oxidation is a chemical reaction that transfers electrons from a substance to an oxidizing agent. Oxidation reactions can produce free radicals. In turn, these radicals can start chain reactions that damage cells. Antioxidants terminate these chain reactions by (e.g. vitamin E Vitamin E is a generic term for tocopherols and tocotrienols. Vitamin E is a family of α-, β-, γ-, and δ- tocopherols and corresponding four tocotrienols. Vitamin E is a fat-soluble antioxidant that stops the production of reactive oxygen species formed when fat undergoes oxidation. Of these, α-tocopherol (also written as alpha-tocopherol) and sometimes vitamin C Vitamin C or L-ascorbic acid or L-ascorbate is an essential nutrient for humans and certain other animal species, in which it functions as a vitamin. In living organisms, ascorbate is an anti-oxidant, since it protects the body against oxidative stress. It is also a cofactor in at least eight enzymatic reactions, including several collagen).^[3] The largest number of vitamins (e.g. B complex The B vitamins are eight water-soluble vitamins that play important roles in cell metabolism. The B vitamins were once thought to be a single vitamin, referred to as vitamin B . Later research showed that they are chemically distinct vitamins that often coexist in the same foods. In general, supplements containing all eight are referred to as a vitamins) function as precursors for enzyme cofactors A cofactor is a non-protein chemical compound that is bound to a protein and is required for the protein's biological activity. These proteins are commonly enzymes, and cofactors can be considered "helper molecules" that assist in biochemical transformations. Cofactors can also be classified depending on how tightly they bind to an, that help enzymes in their work as catalysts Catalysis is the change in rate of a chemical reaction due to the participation of a substance called a catalyst. Unlike other reagents that participate in the chemical reaction, a catalyst is not consumed by the reaction itself. A catalyst may participate in multiple chemical transformations. Catalysts that speed the reaction are called positive in metabolism Metabolism is the set of chemical reactions that happen in living organisms to maintain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into two categories. Catabolism breaks down organic matter, for example to harvest energy in cellular. In this role, vitamins may be tightly bound to enzymes Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process are called substrates, and the enzyme converts them into different molecules, called the products. Almost all processes in a biological cell need enzymes to occur at significant rates. Since enzymes are selective for their as part of prosthetic groups A cofactor is a non-protein chemical compound that is bound to a protein and is required for the protein's biological activity. These proteins are commonly enzymes and cofactors can be considered "helper molecules" that assist in biochemical transformations. Cofactors can also be classified depending on how tightly they bind to an enzyme,: for example, biotin Biotin is a water-soluble B-complex vitamin that is composed of an ureido (tetrahydroimidizalone) ring fused with a tetrahydrothiophene ring. A valeric acid substituent is attached to one of the carbon atoms of the tetrahydrothiophene ring. Biotin is a coenzyme in the metabolism of fatty acids and leucine, and it plays a role in gluconeogenesis is part of enzymes involved in making fatty acids In chemistry, especially biochemistry, a fatty acid is a carboxylic acid with a long unbranched aliphatic tail , which is either saturated or unsaturated. The most occurring natural fatty acids have an even number of carbon atoms because their biosynthesis involves acetyl-CoA, a coenzyme carrying a two-carbon-atom group (see fatty acid synthesis). Alternately, vitamins may also be less tightly bound to enzyme catalysts as coenzymes A cofactor is a non-protein chemical compound that is bound to a protein and is required for the protein's biological activity. These proteins are commonly enzymes, and cofactors can be considered "helper molecules" that assist in biochemical transformations. Cofactors can also be classified depending on how tightly they bind to an, detachable molecules which function to carry chemical groups or electrons between molecules. For example, folic acid Folic acid and folate (the naturally occurring form), as well as pteroyl-L-glutamic acid and pteroyl-L-glutamate, are forms of the water-soluble vitamin B9. Folic acid is itself not biologically active, but its biological importance is due to tetrahydrofolate and other derivatives after its conversion to dihydrofolic acid in the liver carries various forms of carbon group – methyl In chemistry, a methyl group is a hydrophobic alkyl functional group named after methylene (RC , formyl An aldehyde is an organic compound containing a formyl group. This functional group, with the structure R-CHO, consists of a carbonyl centre bonded to hydrogen and an R group. The group without R is called the aldehyde group or formyl group. Aldehydes differ from ketones in that the carbonyl is placed at the end of a carbon skeleton rather than and methylene Methylene groups in a chain or ring contribute to its size and lipophilicity. Methylene was also the old original name for methanol - in the cell. Although these roles in assisting enzyme-substrate reactions are vitamins' best-known function, the other vitamin functions are equally important.^[4]

Until the mid-1930s, when the first commercial yeast-extract and semi-synthetic vitamin C supplement tablets were sold, 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 In chemistry, a chemical substance is a material with a specific chemical composition and made widely available as inexpensive semisynthetic and synthetic-source multivitamin A multivitamin is a preparation intended to supplement a human diet with vitamins, dietary minerals and other nutritional elements. Such preparations are available in the form of tablets, capsules, pastilles, powders, liquids and injectable formulations. Other than injectable formulations, which are only available and administered under medical dietary supplements, since the middle of the 20^th century.

The term vitamin was historically derived from "vitamine," a combination word from vita and amine, meaning amine of life, because it was suggested in 1912 that the organic micronutrient food factors which prevented beriberi and perhaps other similar dietary-deficiency diseases, might be chemical amines Amines are organic compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are derivatives of ammonia, wherein one or more hydrogen atoms have been replaced by a substituent such as an alkyl or aryl group. Important amines include amino acids, biogenic amines, trimethylamine, and aniline; see Category:Amines for. This proved incorrect for the micronutrient class, and the word was shortened to vitamin.

History

The value of eating a certain food to maintain health was recognized long before vitamins were identified. The ancient Egyptians knew that feeding liver to a patient would help cure night blindness, an illness now known to be caused by a vitamin A deficiency.^[5] 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 ships' crews.^[6]

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.^[5] 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.^[5] 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.^[5]

During the late 18th and early 19th centuries, 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". Thus, the first "vitamin" bioactivity ever isolated, which cured rickets, was initially called "vitamin A", although confusingly the bioactivity of this compound is now called vitamin D.^[7] In 1881, Russian surgeon Nikolai Lunin studied the effects of scurvy while at the University of Tartu in present-day Estonia.^[8] 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."^[8] However, his conclusions were rejected by other researchers when they were unable to reproduce his results. One difference was that he had used table sugar (sucrose), while other researchers had used milk sugar (lactose) that still contained small amounts of vitamin B.^{[citation needed]}

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 battleships; 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 mistakenly believed that sufficient amounts of protein prevented it.^[9] 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 beriberi in the chickens. The following year, Frederick Hopkins postulated that some foods contained "accessory factors"—in addition to proteins, carbohydrates, fats, et cetera—that were necessary for the functions of the human body.^[5] Hopkins and Eijkman were awarded the Nobel Prize for Physiology or Medicine in 1929 for their discovery of several vitamins.^[10]

In 1910, the first vitamin complex was isolated by Japanese scientist Umetaro Suzuki who succeeded in extracting a water-soluble complex of micronutrients from rice bran and named it aberic acid (later Orizanin). He published this discovery in a Japanese scientific journal.^[11] 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. In 1912 Polish biochemist Kazimierz Funk isolated the same complex of micronutrients and proposed the complex be named "Vitamine" (a portmanteau of "vital amine").^[12] 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 researchers began to suspect that not all "vitamines" (particularly vitamin A) had an amine component.^[9]

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 anti-scorbutic activity 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 1967, George Wald was awarded the Nobel Prize (along with Ragnar Granit and Haldan Keffer Hartline) for his discovery that vitamin A could participate directly in a physiological process.^[10]

In humans

Vitamins are classified as either water-soluble or fat soluble. In humans there are 13 vitamins: 4 fat-soluble (A, D, E and K) and 9 water-soluble (8 B vitamins and vitamin C). Water-soluble vitamins dissolve easily in water, and in general, are readily excreted from the body, to the degree that urinary output is a strong predictor of vitamin consumption.^[13] Because they are not readily stored, consistent daily intake is important.^[14] Many types of water-soluble vitamins are synthesized by bacteria.^[15] Fat-soluble vitamins are absorbed through the intestinal tract with the help of lipids (fats). Because they are more likely to accumulate in the body, they are more likely to lead to hypervitaminosis than are water-soluble vitamins. Fat-soluble vitamin regulation is of particular significance in cystic fibrosis.^[16]

List of vitamins

Each vitamin is typically used in multiple reactions and, therefore, most have multiple functions.^[17]

In nutrition and diseases

Vitamins 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.^[31]

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 the natural ultraviolet wavelength of 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.^[18]

Once growth and development are completed, vitamins remain essential nutrients for the healthy maintenance of the cells, tissues, and organs that make up a multicellular organism; they also enable a multicellular life form to efficiently use chemical energy provided by food it eats, and to help process the proteins, carbohydrates, and fats required for respiration.^[3]

Deficiencies

Venturi and Venturi^[32][33] suggested that when about 500 million years ago plants and animals began to transfer from the sea to rivers and land, environmental deficiency of marine mineral antioxidants, was a challenge to the evolution of terrestrial life. Terrestrial plants slowly optimized the production of “new” endogenous antioxidants such as ascorbic acid ( Vitamin C), polyphenols, flavonoids, tocopherols etc. Since this age dietary vitamin deficiencies appeared in terrestrial animals. Humans must consume vitamins periodically but with differing schedules, to avoid deficiency. Human bodily stores for different vitamins vary widely; vitamins A, D, and B₁₂ are stored in significant amounts in the human body, mainly in the liver,^[28] and an adult human's diet may be deficient in vitamins A for many months and B₁₂ in some cases for years, before developing a deficiency condition. However, vitamin B₃ (niacin and niacinamide) is not stored in the human body in significant amounts, so stores may only last a couple of weeks.^[19][28] For vitamin C, the first symptoms of scurvy in experimental studies of complete vitamin C deprivation in humans have varied widely, from a month to more than six months, depending on previous dietary history which determined body stores.^[34]

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.^[28] People who eat a varied diet are unlikely to develop a severe primary vitamin deficiency. In contrast, restrictive diets have the potential to cause prolonged vitamin deficits, which may result in often painful and potentially deadly diseases.

Well-known human vitamin deficiencies involve thiamine (beriberi), niacin (pellagra), vitamin C (scurvy) and vitamin D (rickets). In much of the developed world, such deficiencies are rare; this is due to (1) an adequate supply of food; and (2) the addition of vitamins and minerals to common foods, often called fortification.^[18][28] In addition to these classical vitamin deficiency diseases, some evidence has also suggested links between vitamin deficiency and a number of different disorders.^[35][36]

Side effects and overdose

In 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 (vitamin poisoning) from vitamin supplementation does occur. At high enough dosages some vitamins cause side effects such as nausea, diarrhea, and vomiting.^[19][37] When side effects emerge, recovery is often accomplished by reducing the dosage. The doses of vitamins different individual can tolerate varies widely, and appear to be related to age and state of health.^[38]

In 2008, overdose exposure to all formulations of vitamins and multivitamin-mineral formulations was reported by 68,911 individuals to the American Association of Poison Control Centers (nearly 80% of these exposures were in children under the age of 6), leading to 8 "major" life-threatening outcomes and 0 deaths.^[39]

Supplements

Dietary 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 vitamin supplements is well established for certain health conditions, but others need further study.^[40] 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.^[40] Dietary supplements may also contain levels of vitamins many times higher, and in different forms, than one may ingest through food.^[41]

There have been mixed studies on the importance and safety of dietary supplementation. One study released in May 2009 found that antioxidants such as vitamins C and E may actually curb some benefits of exercise.^[42] A meta-analysis published in 2006 suggested that Vitamin A and E supplements not only provide no tangible health benefits for generally healthy individuals, but may actually increase mortality, although two large studies included in the analysis involved smokers, for which it was already known that beta-carotene supplements can be harmful.^[43] National Institutes of Health (NIH) suggests that developments in vitamin E research show that the studies are flawed, and that “evidence for toxicity of a specific form of tocopherol in excess may not be used to conclude that high-dosage "vitamin E" supplementation may increase all-cause mortality.” ^[44] Moreover, NIH states that “the diets of most Americans provide less than the RDA levels of vitamin E.” ^[45] The majority of the medical community appears to agree with popular consensus that dietary supplementation is important. In a peer reviewed study, Council for Responsible Nutrition found that “72 percent of physicians and 89 percent of nurses used dietary supplements and that 79 percent of physicians and 82 percent of nurses said that they recommend dietary supplements to their patients.” ^[46]

Governmental regulation of vitamin supplements

Most 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. Regulation varies depending on the country. In the E.U., the Food Supplements Directive ^[47] requires that only those supplements that have been proven safe can be sold without a prescription.

In the United States, a dietary supplement is defined under the Dietary Supplement Health and Education Act of 1994^[48] (DSHEA). In addition, the Food and Drug Administration (FDA) uses the Adverse Event Reporting System (AERS) ^[49] to monitor for new adverse events and errors that might occur with these marketed supplements. The Federal Food, Drug, and Cosmetic Act (FD&C Act) also requires that manufacturers and distributors who wish to market dietary supplements that contain "new dietary ingredients" give notification to FDA, which must include information that a dietary supplement containing a new ingredient will “reasonably be expected to be safe under the conditions of use recommended or suggested in the labeling.” ^[50]

Many countries have welcomed guidance from International Alliance of Dietary Supplement Associations (IADSA), an expert organization that aims to build an international platform for the development of the food supplement sector worldwide. The climate is constantly changing in the dietary supplement industry, and will most likely continue to evolve. See also the “Regulation” section of Dietary Supplements.

Names in current and previous nomenclatures

The 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 to J were already designated, so the use of the letter K was considered quite reasonable.^[51][53] The table on the right 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.

Anti-Vitamins

Anti-vitamins are chemical compounds that inhibit the absorption or actions of vitamins. For example, avidin is a protein in egg whites that inhibits the absorption of biotin.^[54] Pyrithiamine is similar to thiamine vitamin B1 and inhibits the enzymes that use thiamine.^[55]

See also

• Antioxidant
• Dietary supplement
• Dietetics
• Health freedom movement
• Illnesses related to poor nutrition
• Megavitamin therapy
• Nutrition
  • Vitamin deficiency
  • Dietary minerals
  • Essential amino acids
  • Essential nutrients
  • Nootropics
  • Nutrients
• Orthomolecular medicine
• Pharmacology
• Vitamin poisoning (overdose)
• Whole food supplements

References

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8. ^ ^{a b} 1929 Nobel lecture
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External links

• USDA RDA chart in PDF format
• Health Canada Dietary Reference Intakes Reference Chart for Vitamins
• NIH Office of Dietary Supplements: Fact Sheets
• NIH Office of Dietary Supplements. Dietary Supplements: Background Information

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• Vitamin: Encyclopedia
• Vitamins: Encyclopedia
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