A coordination complex is a chemical compound consisting of a central atom or ion , which is usually metallic and is called the coordination centre , and a surrounding array of bound molecules or ions, that are in turn known as ligands or complexing agents. Many metal-containing compounds , especially those that include transition metals (elements like titanium that belong to the periodic table's d-block ), are coordination complexes.
153-454: Vitamin B 12 , also known as cobalamin , is a water-soluble vitamin involved in metabolism . It is one of eight B vitamins . It is required by animals, which use it as a cofactor in DNA synthesis , and in both fatty acid and amino acid metabolism . It is important in the normal functioning of the nervous system via its role in the synthesis of myelin , and in the circulatory system in
306-482: A dietary supplement or fortified foods for B 12 intake, or risk serious health consequences. Children in some regions of developing countries are at particular risk due to increased requirements during growth coupled with diets low in animal-sourced foods. The US National Academy of Medicine updated estimated average requirements (EARs) and recommended dietary allowances (RDAs) for vitamin B 12 in 1998. The EAR for vitamin B 12 for women and men ages 14 and up
459-484: A complex as ionic and assumes that the ligands can be approximated by negative point charges. More sophisticated models embrace covalency, and this approach is described by ligand field theory (LFT) and Molecular orbital theory (MO). Ligand field theory, introduced in 1935 and built from molecular orbital theory, can handle a broader range of complexes and can explain complexes in which the interactions are covalent . The chemical applications of group theory can aid in
612-414: A complex is not superimposable with its mirror image. It is so called because the two isomers are each optically active , that is, they rotate the plane of polarized light in opposite directions. In the first molecule shown, the symbol Λ ( lambda ) is used as a prefix to describe the left-handed propeller twist formed by three bidentate ligands. The second molecule is the mirror image of the first, with
765-526: A complex is: Examples: The coordination number of ligands attached to more than one metal (bridging ligands) is indicated by a subscript to the Greek symbol μ placed before the ligand name. Thus the dimer of aluminium trichloride is described by Al 2 Cl 4 (μ 2 -Cl) 2 . Any anionic group can be electronically stabilized by any cation. An anionic complex can be stabilised by a hydrogen cation, becoming an acidic complex which can dissociate to release
918-518: 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 . A similar result by Cornelis Adrianus Pekelharing appeared in Dutch medical journal Nederlands Tijdschrift voor Geneeskunde in 1905, but it was not widely reported. In East Asia , where polished white rice
1071-462: A deficiency disease. Even minor deficiencies may cause permanent damage. 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 cellular respiration . For
1224-596: A dietary supplement is taken. A deficiency may be characterized by limb neuropathy or a blood disorder called pernicious anemia , a type of anemia in which red blood cells become abnormally large. This can result in fatigue , decreased ability to think, lightheadedness, shortness of breath, frequent infections , poor appetite , numbness in the hands and feet, depression, memory loss, confusion, difficulty walking , blurred vision , irreversible nerve damage, and many others. If left untreated in infants, deficiency may lead to neurological damage and anemia. Folate levels in
1377-401: A different form known as the constant of destability. This constant is expressed as the inverse of the constant of formation and is denoted as K d = 1/K f . This constant represents the reverse reaction for the decomposition of a complex ion into its individual metal and ligand components. When comparing the values for K d , the larger the value, the more unstable the complex ion is. As
1530-544: A few countries, primarily in Africa, have mandatory food fortification programs for either wheat flour or maize flour; India has a voluntary fortification program. What the nursing mother consumes is more important than her liver tissue content, as it is recently absorbed vitamin that more effectively reaches breast milk. Breast milk B 12 decreases over months of nursing in both well-nourished and vitamin-deficient mothers. Exclusive or near-exclusive breastfeeding beyond six months
1683-593: A large amount of hydroxocobalamin may be given intravenously and sometimes in combination with sodium thiosulfate . The mechanism of action is straightforward: the hydroxycobalamin hydroxide ligand is displaced by the toxic cyanide ion, and the resulting non-toxic cyanocobalamin is excreted in urine . Some research shows that most people in the United States and the United Kingdom consume sufficient vitamin B 12 . However, other research suggests that
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#17327655906931836-452: A ligand-based orbital into an empty metal-based orbital ( ligand-to-metal charge transfer or LMCT). These phenomena can be observed with the aid of electronic spectroscopy; also known as UV-Vis . For simple compounds with high symmetry, the d–d transitions can be assigned using Tanabe–Sugano diagrams . These assignments are gaining increased support with computational chemistry . Superficially lanthanide complexes are similar to those of
1989-518: 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
2142-536: A microbiological assay with Lactobacillus delbrueckii subsp. lactis is used, as the bacteria can utilize the pseudovitamin despite it being unavailable to humans. To get a reliable reading of B 12 content, more advanced techniques are available. One such technique involves pre-separation by silica gel and then assessment with B 12 -dependent E. coli bacteria. A related concept is antivitamin B 12 , compounds (often synthetic B 12 analogues) that not only have no vitamin action, but also actively interfere with
2295-469: A month to more than six months, depending on previous dietary history that determined body stores. 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
2448-440: A much smaller crystal field splitting than in the transition metals. The absorption spectra of an Ln ion approximates to that of the free ion where the electronic states are described by spin-orbit coupling . This contrasts to the transition metals where the ground state is split by the crystal field. Absorptions for Ln are weak as electric dipole transitions are parity forbidden ( Laporte forbidden ) but can gain intensity due to
2601-407: A multicellular organism. Using the genetic blueprint inherited from its parents, a fetus develops 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
2754-532: A necessary amount. A person with cobalamin C disease (which results in combined methylmalonic aciduria and homocystinuria ) may require treatment with intravenous or intramuscular hydroxocobalamin or transdermal B 12 , because oral cyanocobalamin is inadequate in the treatment of cobalamin C disease . Conventional administration does not ensure specific distribution and controlled release of vitamin B 12 . Moreover, therapeutic protocols involving injection require health care people and commuting of patients to
2907-582: A number of different disorders. Some vitamins have documented acute or chronic toxicity at larger intakes, which is referred to as hypertoxicity. The European Union and the governments of several countries have established Tolerable upper intake levels (ULs) for those vitamins which have documented toxicity (see table). The likelihood of consuming too much of any vitamin from food is remote, but excessive intake ( vitamin poisoning ) from dietary supplements does occur. In 2016, overdose exposure to all formulations of vitamins and multi-vitamin/mineral formulations
3060-499: A pair of electrons. There are some donor atoms or groups which can offer more than one pair of electrons. Such are called bidentate (offers two pairs of electrons) or polydentate (offers more than two pairs of electrons). In some cases an atom or a group offers a pair of electrons to two similar or different central metal atoms or acceptors—by division of the electron pair—into a three-center two-electron bond . These are called bridging ligands. Coordination complexes have been known since
3213-637: A prescription. For most vitamins, pharmacopoeial standards 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
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#17327655906933366-480: A regular part of their diet. The elderly are at increased risk because they tend to produce less stomach acid as they age, a condition known as achlorhydria , thereby increasing their probability of B 12 deficiency due to reduced absorption. Nitrous oxide overdose or overuse converts the active monovalent form of vitamin B12 to the inactive bivalent form. The U.S. Recommended Dietary Allowance (RDA) for pregnancy
3519-493: A result of these complex ions forming in solutions they also can play a key role in solubility of other compounds. When a complex ion is formed it can alter the concentrations of its components in the solution. For example: If these reactions both occurred in the same reaction vessel, the solubility of the silver chloride would be increased by the presence of NH 4 OH because formation of the Diammine argentum(I) complex consumes
3672-457: A reversible association of molecules , atoms , or ions through such weak chemical bonds . As applied to coordination chemistry, this meaning has evolved. Some metal complexes are formed virtually irreversibly and many are bound together by bonds that are quite strong. The number of donor atoms attached to the central atom or ion is called the coordination number . The most common coordination numbers are 2, 4, and especially 6. A hydrated ion
3825-483: 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 B 1 , 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
3978-483: A significant portion of the free silver ions from the solution. By Le Chatelier's principle , this causes the equilibrium reaction for the dissolving of the silver chloride, which has silver ion as a product, to shift to the right. This new solubility can be calculated given the values of K f and K sp for the original reactions. The solubility is found essentially by combining the two separate equilibria into one combined equilibrium reaction and this combined reaction
4131-537: A source of vitamin D, as "bottled sunshine", and bananas as a "natural vitality food". They promoted foods such as yeast cakes, a source of B vitamins, on the basis of scientifically determined nutritional value, rather than taste or appearance. In 1942, when flour enrichment with nicotinic acid began, a headline in the popular press said "Tobacco in Your Bread." In response, the Council on Foods and Nutrition of
4284-550: A special category under the general umbrella of foods , not drugs. As a result, the manufacturer, and not the government, has the responsibility of ensuring that its dietary supplement products are safe before they are marketed. Regulation of supplements varies widely by country. In the United States , a dietary supplement is defined under the Dietary Supplement Health and Education Act of 1994. There
4437-634: Is 2.6 micrograms per day (μg/d) , for lactation 2.8 μg/d . Determination of these values was based on an RDA of 2.4 μg/d for non-pregnant women, plus what will be transferred to the fetus during pregnancy and what will be delivered in breast milk. However, looking at the same scientific evidence, the European Food Safety Authority (EFSA) sets adequate intake (AI) at 4.5 μg/d for pregnancy and 5.0 μg/d for lactation. Low maternal vitamin B 12 , defined as serum concentration less than 148 pmol/L, increases
4590-529: Is impaired absorption due to a loss of gastric intrinsic factor (IF) which must be bound to a food-source of B 12 in order for absorption to occur. A second major cause is an age-related decline in stomach acid production ( achlorhydria ), because acid exposure frees protein-bound vitamin. For the same reason, people on long-term antacid therapy, using proton-pump inhibitors , H 2 blockers or other antacids are at increased risk. The diets of vegetarians and vegans may not provide sufficient B 12 unless
4743-534: Is pernicious anemia , characterized by a triad of symptoms : Vitamin B 12 deficiency is most commonly caused by malabsorption, but can also result from low intake, immune gastritis, low presence of binding proteins, or use of certain medications. Vegans —people who choose to not consume any animal-sourced foods—are at risk because plant-sourced foods do not contain the vitamin in sufficient amounts to prevent vitamin deficiency. Vegetarians —people who consume animal byproducts such as dairy products and eggs, but not
Vitamin B12 - Misplaced Pages Continue
4896-492: Is 2.0 μg/day; the RDA is 2.4 μg/d . RDA is higher than EAR so as to identify amounts that will cover people with higher than average requirements. RDA for pregnancy equals 2.6 μg/day. RDA for lactation equals 2.8 μg/d . For infants up to 12 months the adequate intake (AI) is 0.4–0.5 μg/day. (AIs are established when there is insufficient information to determine EARs and RDAs.) For children ages 1–13 years
5049-486: 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. In those who are otherwise healthy, there
5202-420: Is a hydrated-complex ion that consists of six water molecules attached to a metal ion Co. The oxidation state and the coordination number reflect the number of bonds formed between the metal ion and the ligands in the complex ion. However, the coordination number of Pt( en ) 2 is 4 (rather than 2) since it has two bidentate ligands, which contain four donor atoms in total. Any donor atom will give
5355-418: Is a protein in raw egg whites that inhibits the absorption of biotin ; it is deactivated by cooking. Pyrithiamine, a synthetic compound, has a molecular structure similar to thiamine, vitamin B 1 , and inhibits the enzymes that use thiamine. Each vitamin is typically used in multiple reactions, and therefore most have multiple functions. Vitamins are essential for the normal growth and development of
5508-788: Is a strong indicator of low serum vitamin status in nursing infants. This is especially true when the vitamin status was poor during the pregnancy and if the early-introduced foods fed to the still breastfeeding infant are vegan. Risk of deficiency persists if the post-weaning diet is low in animal products. Signs of low vitamin levels in infants and young children can include anemia, poor physical growth and neurodevelopmental delays. Children diagnosed with low serum B 12 can be treated with intramuscular injections, then transitioned to an oral dietary supplement. Various methods of gastric bypass or gastric restriction surgery are used to treat morbid obesity. Roux-en-Y gastric bypass surgery (RYGB) but not sleeve gastric bypass surgery or gastric banding, increases
5661-419: Is a widespread condition that is particularly prevalent in populations with low consumption of animal foods. Such diets can be due to a variety of reasons, such as low socioeconomic status, ethical considerations, or lifestyle choices such as veganism . Foods containing vitamin B 12 include meat, shellfish , liver , fish, poultry , eggs , and dairy products . Many breakfast cereals are fortified with
5814-483: Is adequate or prophylactic B 12 supplementation is given. If the deficiency is detected, metformin can be continued while the deficiency is corrected with B 12 supplements. Vitamin Vitamins are organic molecules (or a set of closely related molecules called vitamers ) that are essential to an organism in small quantities for proper metabolic function. Essential nutrients cannot be synthesized in
5967-466: Is available in 5 mg tablets. The metabolic fate and biological distribution of methylcobalamin are expected to be similar to that of other sources of vitamin B 12 in the diet. The amount of cyanide in cyanocobalamin is generally not a concern, even in the 1,000 μg dose, since the amount of cyanide there (20 μg in a 1,000 μg cyanocobalamin tablet) is less than the daily consumption of cyanide from food, and therefore cyanocobalamin
6120-449: Is conjectured to be a circulating storage function. Several serious, even life-threatening diseases cause elevated serum haptocorrin, measured as abnormally high serum vitamin B 12 , while at the same time potentially manifesting as a symptomatic vitamin deficiency because of insufficient vitamin bound to transcobalamin II which transfers the vitamin to cells. Severe vitamin B 12 deficiency
6273-527: Is cyanocobalamin. Microbial fermentation yields adenosylcobalamin, which is then converted to cyanocobalamin by addition of potassium cyanide or thiocyanate in the presence of sodium nitrite and heat. As of 2019, nineteen countries require food fortification of wheat flour, maize flour or rice with vitamin B 12 . Most of these are in southeast Africa or Central America. Vegan advocacy organizations, among others, recommend that every vegan consume B 12 from either fortified foods or supplements. Vitamin B 12
Vitamin B12 - Misplaced Pages Continue
6426-470: Is displaced by cyanide, creating a non-toxic cyanocobalamin that is excreted in urine. "Pseudovitamin B 12 " refers to compounds that are corrinoids with a structure similar to the vitamin but without vitamin activity. Pseudovitamin B 12 is the majority corrinoid in spirulina , an algal health food sometimes erroneously claimed as having this vitamin activity. Vitamin B 12 deficiency can potentially cause severe and irreversible damage, especially to
6579-480: Is excited by a photon to another d orbital of higher energy, therefore d–d transitions occur only for partially-filled d-orbital complexes (d ). For complexes having d or d configuration, charge transfer is still possible even though d–d transitions are not. A charge transfer band entails promotion of an electron from a metal-based orbital into an empty ligand-based orbital ( metal-to-ligand charge transfer or MLCT). The converse also occurs: excitation of an electron in
6732-431: Is important. Fat-soluble vitamins are absorbed through the gastrointestinal tract with the help of lipids (fats). Vitamins A and D can accumulate in the body, which can result in dangerous hypervitaminosis . Fat-soluble vitamin deficiency due to malabsorption is of particular significance in cystic fibrosis . Anti-vitamins are chemical compounds that inhibit the absorption or actions of vitamins. For example, avidin
6885-555: Is included in multivitamin pills; in some countries grain-based foods such as bread and pasta are fortified with B 12 . In the US, non-prescription products can be purchased providing up to 5,000 μg each, and it is a common ingredient in energy drinks and energy shots , usually at many times the recommended dietary allowance of B 12 . The vitamin can also be supplied on prescription and delivered via injection or other means. Sublingual methylcobalamin , which contains no cyanide ,
7038-613: Is initially corrected with daily intramuscular injections of 1000 μg of the vitamin, followed by maintenance via monthly injections of the same amount or daily oral dosing of 1000 μg . The oral daily dose is far in excess of the vitamin requirement because the normal transporter protein mediated absorption is absent, leaving only very inefficient intestinal passive absorption. Injection side effects include skin rash, itching, chills, fever, hot flushes, nausea and dizziness. Oral maintenance treatment avoids this problem and significantly reduces cost of treatment. For cyanide poisoning,
7191-725: Is little evidence that supplements have any benefits with respect to cancer or heart disease . Vitamin A and E supplements not only provide no health benefits for generally healthy individuals, but they may increase mortality, though the two large studies that support this conclusion included smokers for whom it was already known that beta-carotene supplements can be harmful. A 2018 meta-analysis found no evidence that intake of vitamin D or calcium for community-dwelling elderly people reduced bone fractures. 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
7344-489: Is no FDA approval process for dietary supplements, and no requirement that manufacturers prove the safety or efficacy of supplements introduced before 1994. The Food and Drug Administration must rely on its Adverse Event Reporting System to monitor adverse events that occur with supplements. In 2007, the US Code of Federal Regulations (CFR) Title 21, part III took effect, regulating Good Manufacturing Practices (GMPs) in
7497-455: Is no interaction, the two (or more) individual metal centers behave as if in two separate molecules. Complexes show a variety of possible reactivities: If the ligands around the metal are carefully chosen, the metal can aid in ( stoichiometric or catalytic ) transformations of molecules or be used as a sensor. Metal complexes, also known as coordination compounds, include virtually all metal compounds. The study of "coordination chemistry"
7650-490: Is not conclusive, as it is also seen in people with folate deficiency. In addition, elevated methylmalonic acid levels may also be related to metabolic disorders such as methylmalonic acidemia . If nervous system damage is present and blood testing is inconclusive, a lumbar puncture may be carried out to measure cerebrospinal fluid B 12 levels. Serum haptocorrin binds 80-90% of circulating B 12 , rendering it unavailable for cellular delivery by transcobalamin II . This
7803-432: Is not considered a health risk. Injection of hydroxycobalamin is often used if digestive absorption is impaired, but this course of action may not be necessary with high-dose oral supplements (such as 0.5–1.0 mg or more), because with large quantities of the vitamin taken orally, even the 1% to 5% of free crystalline B 12 that is absorbed along the entire intestine by passive diffusion may be sufficient to provide
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#17327655906937956-495: Is not one of the supplements recommended by the World Health Organization for healthy women who are pregnant, however vitamin B 12 is often suggested during pregnancy in a multivitamin along with folic acid especially for pregnant mothers who follow a vegetarian or vegan diet. Low vitamin concentrations in human milk occur in families with low socioeconomic status or low consumption of animal products. Only
8109-400: Is one kind of a complex ion (or simply a complex), a species formed between a central metal ion and one or more surrounding ligands, molecules or ions that contain at least one lone pair of electrons. If all the ligands are monodentate , then the number of donor atoms equals the number of ligands. For example, the cobalt(II) hexahydrate ion or the hexaaquacobalt(II) ion [Co(H 2 O) 6 ]
8262-444: Is produced in nature by certain bacteria , and archaea . It is synthesized by some bacteria in the gut microbiota in humans and other animals, but it has long been thought that humans cannot absorb this as it is made in the colon , downstream from the small intestine , where the absorption of most nutrients occurs. Ruminants , such as cows and sheep, are foregut fermenters, meaning that plant food undergoes microbial fermentation in
8415-483: Is sometimes referred to as "cobalamins". These chemical compounds have a similar molecular structure, each of which shows vitamin activity in a vitamin-deficient biological system, they are referred to as vitamers . The vitamin activity is as a coenzyme , meaning that its presence is required for some enzyme-catalyzed reactions. Cyanocobalamin is a manufactured form of B 12 . Bacterial fermentation creates AdoB 12 and MeB 12 , which are converted to cyanocobalamin by
8568-689: Is stabilized relative to octahedral structures for six-coordination. The arrangement of the ligands is fixed for a given complex, but in some cases it is mutable by a reaction that forms another stable isomer . There exist many kinds of isomerism in coordination complexes, just as in many other compounds. Stereoisomerism occurs with the same bonds in distinct orientations. Stereoisomerism can be further classified into: Cis–trans isomerism occurs in octahedral and square planar complexes (but not tetrahedral). When two ligands are adjacent they are said to be cis , when opposite each other, trans . When three identical ligands occupy one face of an octahedron,
8721-517: Is sufficient. In the case of vitamin B 12 there is no UL, as there is no human data for adverse effects from high doses. Collectively the EARs, RDAs, AIs and ULs are referred to as dietary reference intakes (DRIs). The European Food Safety Authority (EFSA) refers to the collective set of information as "dietary reference values", with population reference intake (PRI) instead of RDA, and average requirement instead of EAR. AI and UL are defined by EFSA
8874-508: Is synthesized from the amino acid tryptophan . Vitamin C can be synthesized by some species but not by others. Vitamin B 12 is the only vitamin or nutrient not available from plant sources. The Food Fortification Initiative lists countries which have mandatory fortification programs for vitamins folic acid, niacin, vitamin A and vitamins B 1 , B 2 and B 12 . The body's stores for different vitamins vary widely; vitamins A, D, and B 12 are stored in significant amounts, mainly in
9027-410: 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. Coordination complex Coordination complexes are so pervasive that their structures and reactions are described in many ways, sometimes confusingly. The atom within a ligand that is bonded to
9180-448: Is the one that determines the new solubility. So K c , the new solubility constant, is denoted by: As metals only exist in solution as coordination complexes, it follows then that this class of compounds is useful in a wide variety of ways. In bioinorganic chemistry and bioorganometallic chemistry , coordination complexes serve either structural or catalytic functions. An estimated 30% of proteins contain metal ions. Examples include
9333-409: Is the study of "inorganic chemistry" of all alkali and alkaline earth metals , transition metals , lanthanides , actinides , and metalloids . Thus, coordination chemistry is the chemistry of the majority of the periodic table. Metals and metal ions exist, in the condensed phases at least, only surrounded by ligands. The areas of coordination chemistry can be classified according to the nature of
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#17327655906939486-545: The Academy of Nutrition and Dietetics considers plant and algae sources "unreliable", stating that vegans should turn to fortified foods and supplements instead. Natural plant and algae sources of vitamin B 12 include fermented plant foods such as tempeh and seaweed-derived foods such as nori and laverbread . Methylcobalamin has been identified in Chlorella vulgaris . Since only bacteria and some archea possess
9639-607: The American Medical Association approved of the Food and Nutrition Board 's new names niacin and niacin amide for use primarily by non-scientists. It was thought appropriate to choose a name to dissociate nicotinic acid from nicotine , to avoid the perception that vitamins or niacin-rich food contains nicotine, or that cigarettes contain vitamins. The resulting name niacin was derived from ni cotinic ac id + vitam in . Researchers also focused on
9792-497: The Lister Institute of Preventive Medicine . Funk created the name from vital and amine , because it appeared that these organic micronutrient food factors that prevent beriberi and perhaps other similar dietary-deficiency diseases were required for life, hence "vital", and were chemical amines, hence "amine". This was true of thiamine , but after it was found that vitamin C and other such micronutrients were not amines,
9945-596: 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
10098-530: The bioavailability from eggs is less than 9%, compared to 40% to 60% from fish, fowl and meat. Insects are a source of B 12 for animals (including other insects and humans). Animal-derived food sources with a high concentration of vitamin B 12 include liver and other organ meats from lamb , veal , beef , and turkey ; also shellfish and crab meat . There is some evidence that bacterial fermentation of plant foods and symbiotic relationships between algae and bacteria can provide vitamin B 12 . However,
10251-454: The ground state properties. In bi- and polymetallic complexes, in which the individual centres have an odd number of electrons or that are high-spin, the situation is more complicated. If there is interaction (either direct or through ligand) between the two (or more) metal centres, the electrons may couple ( antiferromagnetic coupling , resulting in a diamagnetic compound), or they may enhance each other ( ferromagnetic coupling ). When there
10404-434: The liver , and an adult's diet may be deficient in vitamins A and D for many months and B 12 in some cases for years, before developing a deficiency condition. However, vitamin B 3 (niacin and niacinamide) is not stored in significant amounts, so stores may last only a couple of weeks. For vitamin C, the first symptoms of scurvy in experimental studies of complete vitamin C deprivation in humans have varied widely, from
10557-553: The precursors for them. Vitamins C and E function as antioxidants . Both deficient and excess intake of a vitamin can potentially cause clinically significant illness, although excess intake of water-soluble vitamins is less likely to do so. All the vitamins were discovered between 1913 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
10710-401: The rumen before entering the true stomach ( abomasum ), and thus they are absorbing vitamin B 12 produced by bacteria. Other mammalian species (examples: rabbits , pikas , beaver , guinea pigs ) consume high-fibre plants which pass through the gastrointestinal tract and undergo bacterial fermentation in the cecum and large intestine . In this hindgut fermentation , the material from
10863-498: The European Union (same concept as RDAs), followed by what three government organizations deem to be the safe upper intake. RDAs are set higher than EARs to cover people with higher than average needs. Adequate Intakes (AIs) are set when there is not sufficient information to establish EARs and RDAs. Governments are slow to revise information of this nature. For the U.S. values, with the exception of calcium and vitamin D, all of
11016-597: 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. Once discovered, vitamins were actively promoted in articles and advertisements in McCall's , Good Housekeeping , and other media outlets. Marketers enthusiastically promoted cod-liver oil ,
11169-455: The RDA increases with age from 0.9 to 1.8 μg/day. Because 10 to 30 percent of older people may be unable to effectively absorb vitamin B 12 naturally occurring in foods, it is advisable for those older than 50 years to meet their RDA mainly by consuming foods fortified with vitamin B 12 or a supplement containing vitamin B 12 . As for safety, tolerable upper intake levels (known as ULs) are set for vitamins and minerals when evidence
11322-483: The activity of true vitamin B 12 . The design of these compounds mainly involve replacement of the metal ion with rhodium , nickel , or zinc ; or the attachment of an inactive ligand such as 4-ethylphenyl. These compounds have the potential to be used for analyzing B 12 utilization pathways or even attacking B 12 -dependent pathogens. Gastric acid is needed to release vitamin B 12 from protein for absorption. Reduced secretion of gastric acid and pepsin , from
11475-421: The addition of potassium cyanide in the presence of sodium nitrite and heat. Once consumed, cyanocobalamin is converted to the biologically active AdoB 12 and MeB 12 . The two bioactive forms of vitamin B 12 are methylcobalamin in cytosol and adenosylcobalamin in mitochondria . Cyanocobalamin is the most common form used in dietary supplements and food fortification because cyanide stabilizes
11628-452: The animal must consume sufficient amounts of cobalt . Soil that is deficient in cobalt may result in B 12 deficiency, and B 12 injections or cobalt supplementation may be required for livestock. Animals store vitamin B 12 from their diets in their livers and muscles and some pass the vitamin into their eggs and milk . Meat, liver, eggs and milk are therefore sources of the vitamin for other animals, including humans. For humans,
11781-407: The atom. For alkenes , the pi bonds can coordinate to metal atoms. An example is ethylene in the complex [PtCl 3 (C 2 H 4 )] ( Zeise's salt ). In coordination chemistry, a structure is first described by its coordination number , the number of ligands attached to the metal (more specifically, the number of donor atoms). Usually one can count the ligands attached, but sometimes even
11934-410: The beginning of modern chemistry. Early well-known coordination complexes include dyes such as Prussian blue . Their properties were first well understood in the late 1800s, following the 1869 work of Christian Wilhelm Blomstrand . Blomstrand developed what has come to be known as the complex ion chain theory. In considering metal amine complexes, he theorized that the ammonia molecules compensated for
12087-545: 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 added nutrients . The term "vitamin" was derived from "vitamine", a portmanteau coined in 1912 by the biochemist Casimir Funk while working at
12240-448: The benefits of dietary supplements for persons with certain health conditions. 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. Most countries place dietary supplements in
12393-493: The blood has a lower than normal number of red blood cells, due to a deficiency of vitamin B 12 . The ability to absorb the vitamin declines with age, especially in people over 60. Vitamin B 12 is a coordination complex of cobalt , which occupies the center of a corrin ligand and is further bound to a benzimidazole ligand and adenosyl group. A number of related species are known and these behave similarly, in particular all function as vitamins. This collection of compounds
12546-718: The brain and nervous system. Deficiency at levels only slightly lower than normal can cause a range of symptoms such as fatigue , feeling weak, lightheadedness , dizziness , breathlessness, headaches, mouth ulcers , upset stomach, decreased appetite, difficulty walking (staggering balance problems), muscle weakness, depression , poor memory , poor reflexes, confusion, and pale skin, feeling abnormal sensations , among others, especially in people over age 60. Vitamin B 12 deficiency can also cause symptoms of mania and psychosis . Among other problems, weakened immunity, reduced fertility and interruption of blood circulation in women may occur. The main type of vitamin B12 deficiency anemia
12699-467: The cationic hydrogen. This kind of complex compound has a name with "ic" added after the central metal. For example, H 2 [Pt(CN) 4 ] has the name tetracyanoplatinic (II) acid. The affinity of metal ions for ligands is described by a stability constant, also called the formation constant, and is represented by the symbol K f . It is the equilibrium constant for its assembly from the constituent metal and ligands, and can be calculated accordingly, as in
12852-522: The cecum is expelled as " cecotropes " and are re-ingested, a practice referred to as cecotrophy . Re-ingestion allows for absorption of nutrients made available by bacterial fermentation, and also of vitamins and other nutrients synthesized by the gut bacteria, including vitamin B 12 . Non-ruminant, non-hindgut herbivores may have an enlarged forestomach and/or small intestine to provide a place for bacterial fermentation and B-vitamin production, including B 12 . For gut bacteria to produce vitamin B 12 ,
13005-464: The central atom are called ligands . Ligands are classified as L or X (or a combination thereof), depending on how many electrons they provide for the bond between ligand and central atom. L ligands provide two electrons from a lone electron pair , resulting in a coordinate covalent bond . X ligands provide one electron, with the central atom providing the other electron, thus forming a regular covalent bond . The ligands are said to be coordinated to
13158-411: The central metal atom or ion is called the donor atom . In a typical complex, a metal ion is bonded to several donor atoms, which can be the same or different. A polydentate (multiple bonded) ligand is a molecule or ion that bonds to the central atom through several of the ligand's atoms; ligands with 2, 3, 4 or even 6 bonds to the central atom are common. These complexes are called chelate complexes ;
13311-432: The charge of the ion by forming chains of the type [(NH 3 ) X ] , where X is the coordination number of the metal ion. He compared his theoretical ammonia chains to hydrocarbons of the form (CH 2 ) X . Following this theory, Danish scientist Sophus Mads Jørgensen made improvements to it. In his version of the theory, Jørgensen claimed that when a molecule dissociates in a solution there were two possible outcomes:
13464-624: The chemistry of flavins , which led to the identification of lactoflavin . For their investigations on carotenoids, flavins and vitamins A and B 2 , 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 activity counter to scurvy in his long-established guinea pig scorbutic assay. In 1937, Szent-Györgyi
13617-578: The clinical state of the patient and the results of investigations." The vitamin deficiency is typically suspected when a routine complete blood count shows anemia with an elevated mean corpuscular volume (MCV). In addition, on the peripheral blood smear , macrocytes and hypersegmented polymorphonuclear leukocytes may be seen. Diagnosis is supported based on vitamin B 12 blood levels below 150–180 pmol/L (200–250 pg/mL ) in adults. However, serum values can be maintained while tissue B 12 stores are becoming depleted. Therefore, serum B 12 values above
13770-408: The complexes gives them some important properties: Transition metal complexes often have spectacular colors caused by electronic transitions by the absorption of light. For this reason they are often applied as pigments . Most transitions that are related to colored metal complexes are either d–d transitions or charge transfer bands . In a d–d transition, an electron in a d orbital on the metal
13923-463: The counting can become ambiguous. Coordination numbers are normally between two and nine, but large numbers of ligands are not uncommon for the lanthanides and actinides. The number of bonds depends on the size, charge, and electron configuration of the metal ion and the ligands. Metal ions may have more than one coordination number. Typically the chemistry of transition metal complexes is dominated by interactions between s and p molecular orbitals of
14076-498: The cut-off point of deficiency do not necessarily confirm adequate B 12 status. For this reason, elevated serum homocysteine over 15 micromol/L and methylmalonic acid (MMA) over 0.271 micromol/L are considered better indicators of B 12 deficiency, rather than relying only on the concentration of B 12 in blood. However, elevated MMA is not conclusive, as it is seen in people with B 12 deficiency, but also in elderly people who have renal insufficiency, and elevated homocysteine
14229-425: The daily value was 6.0 μg, but on May 27, 2016, it was revised downward to 2.4 μg. Compliance with the updated labeling regulations was required by 1 January 2020 for manufacturers with US$ 10 million or more in annual food sales, and by 1 January 2021 for manufacturers with lower volume food sales. A table of the old and new adult daily values is provided at Reference Daily Intake . Vitamin B 12
14382-405: The data date to 1997–2004. 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
14535-409: The difference between a coordinated ligand and a charge balancing ion in a compound, for example the chloride ion in the cobaltammine chlorides and to explain many of the previously inexplicable isomers. In 1911, Werner first resolved the coordination complex hexol into optical isomers , overthrowing the theory that only carbon compounds could possess chirality . The ions or molecules surrounding
14688-419: The difference between square pyramidal and trigonal bipyramidal structures. To distinguish between the alternative coordinations for five-coordinated complexes, the τ geometry index was invented by Addison et al. This index depends on angles by the coordination center and changes between 0 for the square pyramidal to 1 for trigonal bipyramidal structures, allowing to classify the cases in between. This system
14841-736: The donor-atoms in the ligands and the d orbitals of the metal ions. The s, p, and d orbitals of the metal can accommodate 18 electrons (see 18-Electron rule ). The maximum coordination number for a certain metal is thus related to the electronic configuration of the metal ion (to be more specific, the number of empty orbitals) and to the ratio of the size of the ligands and the metal ion. Large metals and small ligands lead to high coordination numbers, e.g. [Mo(CN) 8 ] . Small metals with large ligands lead to low coordination numbers, e.g. Pt[P(CMe 3 )] 2 . Due to their large size, lanthanides , actinides , and early transition metals tend to have high coordination numbers. Most structures follow
14994-614: The effect of a low-symmetry ligand field or mixing with higher electronic states ( e.g. d orbitals). f-f absorption bands are extremely sharp which contrasts with those observed for transition metals which generally have broad bands. This can lead to extremely unusual effects, such as significant color changes under different forms of lighting. Metal complexes that have unpaired electrons are paramagnetic . This can be due to an odd number of electrons overall, or to destabilization of electron-pairing. Thus, monomeric Ti(III) species have one "d-electron" and must be (para)magnetic , regardless of
15147-491: 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
15300-467: The first person to receive an award mentioning vitamins, even though it was not specifically about vitamin D. 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
15453-501: The flesh of any animal—are also at risk. Vitamin B 12 deficiency has been observed in between 40% and 80% of the vegetarian population who do not also take a vitamin B 12 supplement or consume vitamin-fortified food. In Hong Kong and India, vitamin B 12 deficiency has been found in roughly 80% of the vegan population. As with vegetarians, vegans can avoid this by consuming a dietary supplement or eating B 12 fortified food such as cereal, plant-based milks, and nutritional yeast as
15606-402: The following example for a simple case: where : x, y, and z are the stoichiometric coefficients of each species. M stands for metal / metal ion , the L for Lewis bases , and finally Z for complex ions. Formation constants vary widely. Large values indicate that the metal has high affinity for the ligand, provided the system is at equilibrium. Sometimes the stability constant will be in
15759-411: The formation of such complexes is called chelation, complexation, and coordination. The central atom or ion, together with all ligands, comprise the coordination sphere . The central atoms or ion and the donor atoms comprise the first coordination sphere. Coordination refers to the "coordinate covalent bonds" ( dipolar bonds ) between the ligands and the central atom. Originally, a complex implied
15912-403: The functions of the human body. 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. When the article was translated into German, the translation failed to state that it
16065-473: The genes and enzymes necessary to synthesize vitamin B 12 , plant and algae sources all obtain the vitamin secondarily from symbiosis with various species of bacteria, or in the case of fermented plant foods, from bacterial fermentation. Foods for which vitamin B 12 -fortified versions are available include breakfast cereals , plant-derived milk substitutes such as soy milk and oat milk , energy bars , and nutritional yeast . The fortification ingredient
16218-468: The geometry or the nature of the ligands. Ti(II), with two d-electrons, forms some complexes that have two unpaired electrons and others with none. This effect is illustrated by the compounds TiX 2 [(CH 3 ) 2 PCH 2 CH 2 P(CH 3 ) 2 ] 2 : when X = Cl , the complex is paramagnetic ( high-spin configuration), whereas when X = CH 3 , it is diamagnetic ( low-spin configuration). Ligands provide an important means of adjusting
16371-470: The hospital thus increasing the cost of the treatment and impairing the lifestyle of patients. Targeted delivery of vitamin B 12 is a major focus of modern prescriptions. For example, conveying the vitamin to the bone marrow and nerve cells would help myelin recovery. Currently, several nanocarriers strategies are being developed for improving vitamin B 12 delivery with the aim to simplify administration, reduce costs, improve pharmacokinetics, and ameliorate
16524-406: The hypothesis that other diseases, such as rickets, pellagra, coeliac disease, and scurvy could also be cured by vitamins. Max Nierenstein a friend and Reader of Biochemistry at Bristol University reportedly suggested the "vitamine" name (from "vital amine"). The name soon became synonymous with Hopkins' "accessory factors", and, by the time it was shown that not all vitamins are amines , the word
16677-441: The individual may affect the course of pathological changes and symptomatology of vitamin B 12 deficiency. Vitamin B 12 deficiency in pregnant women is strongly associated with an increased risk of spontaneous abortion, congenital malformations such as neural tube defects, problems with brain development growth in the unborn child. Vitamin B 12 was discovered as a result of pernicious anemia, an autoimmune disorder in which
16830-453: The intensely colored vitamin B 12 , the heme group in hemoglobin , the cytochromes , the chlorin group in chlorophyll , and carboxypeptidase , a hydrolytic enzyme important in digestion. Another complex ion enzyme is catalase , which decomposes the cell's waste hydrogen peroxide . Synthetic coordination compounds are also used to bind to proteins and especially nucleic acids (e.g. anticancer drug cisplatin ). Homogeneous catalysis
16983-443: The ions were to form a chain, this would occur outside of the coordination sphere while the ions that bound directly to the metal would do so within the coordination sphere. In one of his most important discoveries however Werner disproved the majority of the chain theory. Werner discovered the spatial arrangements of the ligands that were involved in the formation of the complex hexacoordinate cobalt. His theory allows one to understand
17136-485: The ions would bind via the ammonia chains Blomstrand had described or the ions would bind directly to the metal. It was not until 1893 that the most widely accepted version of the theory today was published by Alfred Werner . Werner's work included two important changes to the Blomstrand theory. The first was that Werner described the two possibilities in terms of location in the coordination sphere. He claimed that if
17289-406: The isomer is said to be facial, or fac . In a fac isomer, any two identical ligands are adjacent or cis to each other. If these three ligands and the metal ion are in one plane, the isomer is said to be meridional, or mer . A mer isomer can be considered as a combination of a trans and a cis , since it contains both trans and cis pairs of identical ligands. Optical isomerism occurs when
17442-520: The ligands are water molecules. It is true that the focus of mineralogy, materials science, and solid state chemistry differs from the usual focus of coordination or inorganic chemistry. The former are concerned primarily with polymeric structures, properties arising from a collective effects of many highly interconnected metals. In contrast, coordination chemistry focuses on reactivity and properties of complexes containing individual metal atoms or small ensembles of metal atoms. The basic procedure for naming
17595-415: The ligands, in broad terms: Mineralogy , materials science , and solid state chemistry – as they apply to metal ions – are subsets of coordination chemistry in the sense that the metals are surrounded by ligands. In many cases these ligands are oxides or sulfides, but the metals are coordinated nonetheless, and the principles and guidelines discussed below apply. In hydrates , at least some of
17748-507: 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. In the European Union, the Food Supplements Directive requires that only those supplements that have been proven safe can be sold without
17901-413: The maturation of red blood cells in the bone marrow . Plants do not need cobalamin and carry out the reactions with enzymes that are not dependent on it. Vitamin B 12 is the most chemically complex of all vitamins, and for humans the only vitamin that must be sourced from animal-derived foods or supplements. Only some archaea and bacteria can synthesize vitamin B 12 . Vitamin B 12 deficiency
18054-415: The molecule against degradation. Methylcobalamin is also offered as a dietary supplement. There is no advantage to the use of adenosylcobalamin or methylcobalamin forms for the treatment of vitamin B 12 deficiency. Hydroxocobalamin can be injected intramuscularly to treat vitamin B 12 deficiency. It can also be injected intravenously for the purpose of treating cyanide poisoning, as the hydroxyl group
18207-446: The most part, vitamins are obtained from the diet, but some are acquired by other means: for example, microorganisms in the gut flora produce vitamin K and biotin; and one form of vitamin D is synthesized in skin cells when they are exposed to a certain wavelength of ultraviolet light present in sunlight . Humans can produce some vitamins from precursors they consume: for example, vitamin A is synthesized from beta carotene ; and niacin
18360-444: The need to ensure adequate nutrition, especially to compensate for what was lost in the manufacture of processed foods . 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,
18513-543: 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
18666-482: 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 tocopherols and four tocotrienols . The term vitamin does not include
18819-443: The percentage losses of various nutrients from food types and cooking methods. Some vitamins may become more "bio-available" – that is, usable by the body – when foods are cooked. The table below shows whether various vitamins are susceptible to loss from heat—such as heat from boiling, steaming, frying, etc. The effect of cutting vegetables can be seen from exposure to air and light. Water-soluble vitamins such as B and C dissolve into
18972-451: The person's dietary intake is below recommended levels. Symptomatic vitamin deficiency is more likely if the person is rendered achlorhydric (a complete absence of gastric acid secretion), which occurs more frequently with proton pump inhibitors than H 2 blockers. Reduced serum levels of vitamin B 12 occur in up to 30% of people taking long-term anti-diabetic metformin . Deficiency does not develop if dietary intake of vitamin B 12
19125-415: The points-on-a-sphere pattern (or, as if the central atom were in the middle of a polyhedron where the corners of that shape are the locations of the ligands), where orbital overlap (between ligand and metal orbitals) and ligand-ligand repulsions tend to lead to certain regular geometries. The most observed geometries are listed below, but there are many cases that deviate from a regular geometry, e.g. due to
19278-462: The properties of transition metal complexes are dictated by their electronic structures. The electronic structure can be described by a relatively ionic model that ascribes formal charges to the metals and ligands. This approach is the essence of crystal field theory (CFT). Crystal field theory, introduced by Hans Bethe in 1929, gives a quantum mechanically based attempt at understanding complexes. But crystal field theory treats all interactions in
19431-494: The proportion of people with low or marginal levels of vitamin B 12 is up to 40% in the Western world . Grain -based foods can be fortified by having the vitamin added to them. Vitamin B 12 supplements are available as single or multivitamin tablets. Pharmaceutical preparations of vitamin B 12 may be given by intramuscular injection . Since there are few non-animal sources of the vitamin, vegans are advised to consume
19584-711: The quality of patients' lives. Pseudovitamin-B 12 refers to B 12 -like analogues that are biologically inactive in humans. Most cyanobacteria, including Spirulina , and some algae, such as Porphyra tenera (used to make a dried seaweed food called nori in Japan), have been found to contain mostly pseudovitamin-B 12 instead of biologically active B 12 . These pseudo-vitamin compounds can be found in some types of shellfish, in edible insects, and at times as metabolic breakdown products of cyanocobalamin added to dietary supplements and fortified foods. Pseudovitamin-B 12 can show up as biologically active vitamin B 12 when
19737-709: The risk of miscarriage, preterm birth and newborn low birth weight. During pregnancy the placenta concentrates B 12 , so that newborn infants have a higher serum concentration than their mothers. As it is recently absorbed vitamin content that more effectively reaches the placenta, the vitamin consumed by the mother-to-be is more important than that contained in her liver tissue. Women who consume little animal-sourced food, or who are vegetarian or vegan, are at higher risk of becoming vitamin depleted during pregnancy than those who consume more animal products. This depletion can lead to anemia, and also an increased risk that their breastfed infants become vitamin deficient. Vitamin B 12
19890-431: The risk of vitamin B 12 deficiency and requires preventive post-operative treatment with either injected or high-dose oral supplementation. For post-operative oral supplementation, 1000 μg/d may be needed to prevent vitamin deficiency. According to one review: "At present, no 'gold standard' test exists for the diagnosis of vitamin B 12 deficiency and as a consequence the diagnosis requires consideration of both
20043-529: The same as in the United States. For women and men over age 18 the adequate intake (AI) is set at 4.0 μg/day. AI for pregnancy is 4.5 μg/day, for lactation 5.0 μg/day. For children aged 1–14 years the AIs increase with age from 1.5 to 3.5 μg/day. These AIs are higher than the U.S. RDAs. The EFSA also reviewed the safety question and reached the same conclusion as in the United States—that there
20196-456: The symbol Δ ( delta ) as a prefix for the right-handed propeller twist. The third and fourth molecules are a similar pair of Λ and Δ isomers, in this case with two bidentate ligands and two identical monodentate ligands. Structural isomerism occurs when the bonds are themselves different. Four types of structural isomerism are recognized: ionisation isomerism, solvate or hydrate isomerism, linkage isomerism and coordination isomerism. Many of
20349-517: 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
20502-421: The transition metals in that some are colored. However, for the common Ln ions (Ln = lanthanide) the colors are all pale, and hardly influenced by the nature of the ligand. The colors are due to 4f electron transitions. As the 4f orbitals in lanthanides are "buried" in the xenon core and shielded from the ligand by the 5s and 5p orbitals they are therefore not influenced by the ligands to any great extent leading to
20655-408: The understanding of crystal or ligand field theory, by allowing simple, symmetry based solutions to the formal equations. Chemists tend to employ the simplest model required to predict the properties of interest; for this reason, CFT has been a favorite for the discussions when possible. MO and LF theories are more complicated, but provide a more realistic perspective. The electronic configuration of
20808-558: The use of H 2 blocker or proton-pump inhibitor (PPI) drugs, can reduce absorption of protein-bound (dietary) vitamin B 12 , although not of supplemental vitamin B 12 . H 2 -receptor antagonist examples include cimetidine , famotidine , nizatidine , and ranitidine . PPIs examples include omeprazole , lansoprazole , rabeprazole , pantoprazole , and esomeprazole . Clinically significant vitamin B 12 deficiency and megaloblastic anemia are unlikely, unless these drug therapies are prolonged for two or more years, or if in addition
20961-435: The use of ligands of diverse types (which results in irregular bond lengths; the coordination atoms do not follow a points-on-a-sphere pattern), due to the size of ligands, or due to electronic effects (see, e.g., Jahn–Teller distortion ): The idealized descriptions of 5-, 7-, 8-, and 9- coordination are often indistinct geometrically from alternative structures with slightly differing L-M-L (ligand-metal-ligand) angles, e.g.
21114-426: 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
21267-482: The vitamin. Supplements and medications are available to treat and prevent vitamin B 12 deficiency. They are usually taken by mouth, but for the treatment of deficiency may also be given as an intramuscular injection . Vitamin B 12 deficiencies have a greater effect on young children, pregnant and elderly people, and are more common in middle and lower developed countries due to malnutrition. The most common cause of vitamin B 12 deficiency in developed countries
21420-576: The water when a vegetable is boiled, and are then lost when the water is discarded. In setting human nutrient guidelines, government organizations do not necessarily agree on amounts needed to avoid deficiency or maximum amounts to avoid the risk of toxicity. For example, for vitamin C, recommended intakes range from 40 mg/day in India to 155 mg/day for the European Union. The table below shows U.S. Estimated Average Requirements (EARs) and Recommended Dietary Allowances (RDAs) for vitamins, PRIs for
21573-579: The word was shortened to "vitamin" in English. 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. Because they are not as readily stored, more consistent intake
21726-514: Was a newly discovered nutrient, a claim made in the original Japanese article, and hence his discovery failed to gain publicity. In 1912 Polish-born biochemist Casimir Funk , working in London, isolated the same complex of micronutrients and proposed the complex be named "vitamine". It was later to be known as vitamin B 3 (niacin), though he described it as "anti-beri-beri-factor" (which would today be called thiamine or vitamin B 1 ). Funk proposed
21879-469: Was already ubiquitous. In 1920, Jack Cecil Drummond proposed that the final "e" be dropped to deemphasize the "amine" reference, hence "vitamin", after researchers began to suspect that not all "vitamines" (in particular, vitamin A) have an amine component. The Nobel Prize for Chemistry for 1928 was awarded to Adolf Windaus "for his studies on the constitution of the sterols and their connection with vitamins",
22032-689: 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 B 2 and B 6 . Five people have been awarded Nobel Prizes for direct and indirect studies of vitamin B 12 : 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
22185-536: 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
22338-648: Was followed in the 1950s by the mass production and marketing of vitamin supplements , including multivitamins , to prevent vitamin deficiencies in the general population. Governments have mandated the addition of some vitamins to staple foods 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 . from plant origin as provitamin A / all- trans -beta-carotene: orange, ripe yellow fruits, leafy vegetables, carrots, pumpkin, squash, spinach The value of eating certain foods to maintain health
22491-414: 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
22644-427: Was later extended to four-coordinated complexes by Houser et al. and also Okuniewski et al. In systems with low d electron count , due to special electronic effects such as (second-order) Jahn–Teller stabilization, certain geometries (in which the coordination atoms do not follow a points-on-a-sphere pattern) are stabilized relative to the other possibilities, e.g. for some compounds the trigonal prismatic geometry
22797-476: Was not sufficient evidence to set a UL for vitamin B 12 . The Japan National Institute of Health and Nutrition set the RDA for people ages 12 and older at 2.4 μg/day. The World Health Organization also uses 2.4 μg/day as the adult recommended nutrient intake for this vitamin. For U.S. food and dietary supplement labeling purposes, the amount in a serving is expressed as a "percent of daily value" (%DV). For vitamin B 12 labeling purposes, 100% of
22950-477: Was recognized long before vitamins were identified. The ancient Egyptians knew that feeding liver to a person may help with night blindness , an illness now known to be caused by a vitamin A deficiency. The advance of ocean voyages during the Age of Discovery resulted in prolonged periods without access to fresh fruits and vegetables, and made illnesses from vitamin deficiency common among ships' crews. In 1747,
23103-530: Was reported by 63,931 individuals to the American Association of Poison Control Centers with 72% of these exposures in children under the age of five. In the US, analysis of a national diet and supplement survey reported that about 7% of adult supplement users exceeded the UL for folate and 5% of those older than age 50 years exceeded the UL for vitamin A. The USDA has conducted extensive studies on
23256-505: Was that scurvy was caused by "tainted" canned food . In 1881, Russian 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 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
23409-581: Was the common staple food of the middle class, beriberi resulting from lack of vitamin B 1 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
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