|
[[دوتنه:La Boqueria.JPG|thumb|350px|[[مېوه|مېوې]] او [[سابه]] اکثرا د ويټامينونو د غوره سرچينې په توګه کارول کيږي.]]
{{ژباړل}}
[[دوتنه:La Boqueria.JPG|thumb|350px|[[Fruit]]s and [[vegetable]]s are often a good source of vitamins.]]
A '''vitamin''' is an [[organic compound]] required as a [[nutrient]] in tiny amounts by an [[organism]].<ref name="Lieberman">Lieberman, S, Bruning, N (1990). The Real Vitamin & Mineral Book. NY: Avery Group, 3.</ref> A compound is called a vitamin when it cannot be [[biosynthesis|synthesized]] in sufficient quantities by an organism, and must be obtained from the diet. Thus, the term is conditional both on the circumstances and the particular organism. For example, [[ascorbic acid]] functions as [[vitamin C]] for some animals but not others, and [[vitamin D|vitamins D]] and [[vitamin K|K]] are required in the human diet only in certain circumstances.<ref>[http://www.thefreedictionary.com/vitamin vitamin - definition of vitamin by the Free Online Dictionary, Thesaurus and Encyclopedia<!-- Bot generated title -->]</ref> The term ''vitamin'' does not include other [[essential nutrient]]s such as [[dietary minerals]], [[essential fatty acid]]s, or [[essential amino acid]]s, nor does it encompass the large number of other nutrients that promote health but are otherwise required less often.<ref>{{cite book
| last = Maton
| first = Anthea
| authorlink =
| coauthors = Jean Hopkins, Charles William McLaughlin, Susan Johnson, Maryanna Quon Warner, David LaHart, Jill D. Wright
| title = Human Biology and Health
| publisher = Prentice Hall
| year = 1993
| location = Englewood Cliffs, New Jersey, USA
| pages =
| url =
| doi =
| id =
| isbn = 0-13-981176-1
| oclc = 32308337}}</ref>
Vitamins are classified by their biological and chemical activity, not their structure. Thus, each "vitamin" may refer to several ''[[vitamer]]'' 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," which includes the compounds [[retinal]], [[retinol]], and many [[carotenoid]]s.<ref>
{{cite web
|url=http://www.answers.com/topic/vitamer?cat=health#top
|title=vitamer: Definition and Much More from Answers.com
|publisher=www.answers.com
|accessdate=2008-06-16
|last=
|first=
}}
</ref> Vitamers are often inter-converted in the body.
Vitamins have diverse biochemical functions, including function as [[hormones]] (e.g. vitamin D), [[antioxidants]] (e.g. vitamin E), and mediators of cell signaling and regulators of cell and tissue growth and differentiation (e.g. vitamin A).<ref>[http://www3.cambridge.org/uk/catalogue/catalogue.asp?isbn=9780521803885. Accessed Jan 4, 2008] </ref> The largest number of vitamins (e.g. B complex vitamins) function as precursors for enzyme [[cofactor (biochemistry)|cofactor]] [[biomolecule|bio-molecules]] ([[coenzyme]]s), that help act as [[catalyst]]s and [[Substrate (chemistry)|substrates]] in [[metabolism]]. When acting as part of a catalyst, vitamins are bound to [[enzyme]]s and are called [[prosthetic group]]s. For example, [[biotin]] is part of enzymes involved in making [[fatty acid]]s. Vitamins also act as [[coenzymes]] to carry chemical groups between enzymes. For example, [[folic acid]] carries various forms of carbon group – [[methyl]], [[formyl]] and [[methylene]] - in the cell. Although these roles in assisting enzyme reactions are vitamins' best-known function, the other vitamin functions are equally important.<ref>{{cite journal |author=Bolander FF |title=Vitamins: not just for enzymes |journal=Curr Opin Investig Drugs |volume=7 |issue=10 |pages=912–5 |year=2006 |pmid=17086936}}</ref>
Until the 1900s, vitamins were obtained solely through food intake, and changes in diet (which, for example, could occur during a particular growing season) can alter the types and amounts of vitamins ingested. Vitamins have been produced as commodity [[chemicals]] and made widely available as inexpensive pills for several decades,<ref name="Kirk-Othmer">Kirk-Othmer (1984). Encyclopedia of Chemical Technology Third Edition. NY: John Wiley and Sons, Vol. 24:104.</ref> allowing supplementation of the dietary intake.
[[دوتنه:All-trans-Retinol2.svg|thumb|350px|right|Retinol (one [[vitamer]] of [[Vitamin A]])]]
== تاريخ ==
[[انځور:ARS copper rich foods.jpg|thumb|right|350px|The [[Ancient Egyptians]] knew that feeding a patient [[liver]] (back, right) would help cure [[Nyctalopia|night blindness]].]]
The value of eating a certain food to maintain health was recognized long before vitamins were identified. The ancient [[Egypt]]ians knew that feeding [[liver]] to a patient would help cure [[night blindness]], an illness now known to be caused by a [[vitamin A]] deficiency.<ref name="Challem"/> 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.
In 1749, the [[Scotland|Scottish]] [[surgeon]] [[James Lind (physician)|James Lind]] discovered that [[citrus]] foods helped prevent [[scurvy]], a particularly deadly disease in which [[collagen]] is not properly formed, causing poor wound healing, bleeding of the [[gingiva|gums]], severe pain, and death.<ref name="Challem">Jack Challem (1997). [http://www.thenutritionreporter.com/history_of_vitamins.html "The Past, Present and Future of Vitamins"]</ref> In 1753, Lind published his ''Treatise on the Scurvy'', which recommended using [[lemon]]s and [[lime]]s 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.<ref name="Challem"/> As a result, Arctic expeditions continued to be plagued by scurvy and other [[deficiency disease]]s. In the early 20th century, when [[Robert Falcon Scott]] made his two expeditions to the [[Antarctic]], the prevailing medical theory was that scurvy was caused by "tainted" [[canning|canned food]].<ref name="Challem"/>
In 1881, [[Russia]]n surgeon Nikolai Lunin studied the effects of scurvy while at the [[University of Tartu]] in present-day Estonia.<ref name="nobel">[http://nobelprize.org/medicine/laureates/1929/hopkins-lecture.html 1929 Nobel lecture]</ref> He fed [[mouse|mice]] an artificial mixture of all the separate constituents of [[milk]] known at that time, namely the [[protein]]s, [[fat]]s, [[carbohydrate]]s, and [[salt]]s. 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."<ref name="nobel"/> 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 ([[سرچينه]]), while other researchers had used milk sugar ([[lactose]]) that still contained small amounts of [[vitamin B]].
{| class="wikitable" style = "float:left; font-size:90%; margin-left:15px"
|+ The discovery of vitamins and their sources
|- class="hintergrundfarbe6"
! د موندني كال !! ويټامين !! سرچينه
|-
| 1909 || Vitamin A ([[Retinol]]) || [[Cod liver oil]]
|-
| 1912 || Vitamin B<sub>1</sub> ([[Thiamine]]) || [[Rice bran]]
|-
| 1912 || Vitamin C ([[Ascorbic acid]]) || [[Lemon]]s
|-
| 1918 || Vitamin D ([[Calciferol]]) || [[Cod liver oil]]
|-
| 1920 || Vitamin B<sub>2</sub> ([[Riboflavin]]) || [[Egg (food)|Eggs]]
|-
| 1922 || Vitamin E ([[Tocopherol]]) || [[Wheat germ oil]], [[Cosmetic]] and [[Liver]]
|-
| 1926 || [[Vitamin B12|Vitamin B<sub>12</sub>]] (Cyanocobalamin) || [[Liver]]
|-
| 1929 || [[Vitamin K]] (Phylloquinone) || [[Alfalfa]]
|-
| 1931 || Vitamin B<sub>5</sub> ([[Pantothenic acid]]) || [[Liver]]
|-
| 1931 || Vitamin B<sub>7</sub> ([[Biotin]]) || [[Liver]]
|-
| 1934 || Vitamin B<sub>6</sub> ([[Pyridoxine]]) || [[Rice bran]]
|-
| 1936 || Vitamin B<sub>3</sub> ([[Niacin]]) || [[Liver]]
|-
| 1941 || Vitamin B<sub>9</sub> ([[Folic acid]]) || [[Liver]]
|}
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 [[Japanese Navy]], observed that beriberi was endemic among low-ranking crew who often ate nothing but rice, but not among crews of Western navies and officers who consumed a Western-style diet. Kanehiro initially believed that lack of protein was the chief cause of beriberi. With the support of the Japanese navy, he experimented using crews of two [[battleship]]s; 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 Kanehiro and the Japanese Navy that diet was the cause of beriberi. This was confirmed in 1897, when [[Christiaan Eijkman]] 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.<ref name="Challem"/> Hopkins was awarded the 1929 [[Nobel Prize for Physiology or Medicine]] with Christiaan Eijkman for their discovery of several vitamins.
In 1910, Japanese scientist [[Umetaro Suzuki]] succeeded in extracting a water-soluble complex of micronutrients from rice bran and named it [[aberic acid]]. He published this discovery in a Japanese scientific journal.<ref>[http://www.journalarchive.jst.go.jp/english/jnlabstract_en.php?cdjournal=nikkashi1880&cdvol=32&noissue=1&startpage=4 Tokyo Kagaku Kaishi: (1911)<!-- Bot generated title -->]</ref>
When the article was translated into German, the translation failed to state that it was a newly discovered nutrient, a claim made in the original Japanese article, and hence his discovery failed to gain publicity. Polish biochemist [[Kazimierz Funk]] isolated the same complex of micronutrients and proposed the complex be named "Vitamine" (a [[portmanteau]] of "vital amine") in 1912.<ref>Funk, C. and H. E. Dubin. The Vitamines. Baltimore: Williams and Wilkins Company, 1922.</ref> The name soon became synonymous with Hopkins' "accessory factors", and by the time it was shown that not all vitamins were [[amine]]s, the word was already ubiquitous. In 1920, [[Jack Cecil Drummond]] proposed that the final "e" be dropped to deemphasize the "amine" reference after the discovery that [[vitamin C]] had no amine component.
Throughout the early 1900s, the use of deprivation studies allowed scientists to isolate and identify a number of vitamins. Initially, lipid from [[fish oil]] was used to cure [[rickets]] in [[rat]]s, 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]].<ref>Bellis, Mary. [http://inventors.about.com/library/inventors/bl_vitamins.htm Vitamins - Production Methods The History of the Vitamins]. Retrieved 1 February 2005.</ref> What we now call "vitamin A" was identified in fish oil as a separate factor that was inactivated by [[ultraviolet]] light. In 1931, [[Albert Szent-Györgyi]] and a fellow researcher Joseph Svirbely determined that "hexuronic acid" was actually [[vitamin C]] and noted its anti-[[scurvy|scorbutic]] activity. In 1937, Szent-Györgyi was awarded the [[Nobel Prize in Physiology or Medicine|Nobel Prize]] for his discovery. In 1943 [[Edward Adelbert Doisy]] and [[Henrik Dam]] were awarded the [[Nobel Prize in Physiology or Medicine|Nobel Prize]] for their discovery of [[vitamin K]] and its chemical structure.
== په انسانانو كي ==
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 ===
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.<ref name="pmid18635909">{{cite journal |author=Fukuwatari T, Shibata K |title=Urinary water-soluble vitamins and their metabolite contents as nutritional markers for evaluating vitamin intakes in young Japanese women |journal=J. Nutr. Sci. Vitaminol. |volume=54 |issue=3 |pages=223–9 |year=2008 |month=June |pmid=18635909 |doi= 10.3177/jnsv.54.223|url=http://joi.jlc.jst.go.jp/JST.JSTAGE/jnsv/54.223?from=PubMed |format={{dead link|date=April 2009}} – <sup>[http://scholar.google.co.uk/scholar?hl=en&lr=&q=intitle%3AUrinary+water-soluble+vitamins+and+their+metabolite+contents+as+nutritional+markers+for+evaluating+vitamin+intakes+in+young+Japanese+women&as_publication=J.+Nutr.+Sci.+Vitaminol.&as_ylo=2008&as_yhi=2008&btnG=Search Scholar search]</sup>}}</ref> Because they are not readily stored, consistent daily intake is important.<ref name="urlWater-Soluble Vitamins">{{cite web |url=http://www.ext.colostate.edu/PUBS/FOODNUT/09312.html |title=Water-Soluble Vitamins |format= |work= |accessdate=2008-12-07}}</ref> Many types of water-soluble vitamins are synthesized by bacteria.<ref name="pmid16462170">{{cite journal |author=Said HM, Mohammed ZM |title=Intestinal absorption of water-soluble vitamins: an update |journal=Curr. Opin. Gastroenterol. |volume=22 |issue=2 |pages=140–6 |year=2006 |month=March |pmid=16462170 |doi=10.1097/01.mog.0000203870.22706.52 |url=http://meta.wkhealth.com/pt/pt-core/template-journal/lwwgateway/media/landingpage.htm?an=00001574-200603000-00011}}</ref>
=== Fat-soluble ===
[[Fat]]-soluble vitamins are absorbed through the [[intestinal tract]] with the help of [[lipid]]s (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]].<ref name="pmid18812835">{{cite journal |author=Maqbool A, Stallings VA |title=Update on fat-soluble vitamins in cystic fibrosis |journal=Curr Opin Pulm Med |volume=14 |issue=6 |pages=574–81 |year=2008 |month=November |pmid=18812835 |doi=10.1097/MCP.0b013e3283136787 |url=http://meta.wkhealth.com/pt/pt-core/template-journal/lwwgateway/media/landingpage.htm?an=00063198-200811000-00012}}</ref>
=== د ويټامينونو لړليك ===
Each vitamin is typically used in multiple reactions and, therefore, most have multiple functions.<ref name="Kutsky">Kutsky, R.J. (1973). Handbook of Vitamins and Hormones. New York:Van Nostrand Reinhold.</ref>
{| class="wikitable sortable" style="margin: 1em auto 1em auto"
! ويټامين generic</br> descriptor name
! width= "125"|[[Vitamer]] chemical name(s) (list not complete)
! width= "75"|[[Solubility]]
! class="unsortable" width= "150"|[[Reference Daily Intake|Recommended dietary allowances]]<br />(male, age 19–70)<ref name="RDA">[http://www.iom.edu/Object.File/Master/7/296/0.pdf Dietary Reference Intakes: Vitamins] The National Academies, 2001.</ref>
! class="unsortable" width= "200"| Deficiency disease
! class="unsortable" width= "100"|Upper Intake Level<br /> (UL/day)<ref name="RDA"/>
! class="unsortable" width= "250"| Overdose disease
|-
! [[ويټامين A]]
| [[Retinoids]]<br />([[retinol]], [[retinoids]]<br />and [[carotenoid]]s)
| Fat
| '''900 µg'''
| [[Night-blindness]] and<br /> [[Keratomalacia]]<ref name="GOVa">[http://dietary-supplements.info.nih.gov/factsheets/vitamina.asp Vitamin and Mineral Supplement Fact Sheets Vitamin A]</ref>
| 3,000 µg
| [[Hypervitaminosis A]]
|-
! [[Thiamine|Vitamin B<sub>1</sub>]]
| [[Thiamine]]
| Water
| '''1.2 mg'''
| [[Beriberi]], [[Wernicke-Korsakoff syndrome]]
| N/D<ref>N/D= "Amount not determinable due to lack of data of adverse effects. Source of intake should be from food only to prevent high levels of intake"(see [http://www.iom.edu/Object.File/Master/7/296/0.pdf Dietary Reference Intakes: Vitamins]).</ref>
| Rare hypersensitive reactions resembling anaphylactic shock—injection only; drowsiness
|-
! [[Riboflavin|Vitamin B<sub>2</sub>]]
| [[Riboflavin]]
| Water
| '''1.3 mg'''
| [[Ariboflavinosis]]
| N/D
| Any or all of itching, numbness, [[paresthesia]], fatigue, chartreuse-yellow urine discoloration, and in extreme cases nausea, vomiting, low blood pressure and anemia.
|-
! [[Niacin|Vitamin B<sub>3</sub>]]
| [[Niacin]], [[niacinamide]]
| Water
| '''16.0 mg'''
| [[Pellagra]]
| 35.0 mg
| [[Liver]] damage (doses > 2g/day)<ref>J.G. Hardman et al., eds., ''Goodman and Gilman's Pharmacological Basis of Therapeutics, 10th ed.'', p.992.</ref> and [[Niacin#Toxicity|other problems]]
|-
! [[Pantothenic acid|Vitamin B<sub>5</sub>]]
| [[Pantothenic acid]]
| Water
| 5.0 mg<ref>Plain type indicates Adequate Intakes (A/I). "The AI is believed to cover the needs of all individuals, but a lack of data prevent being able to specify with confidence the percentage of individuals covered by this intake" (see [http://www.iom.edu/Object.File/Master/7/296/0.pdf Dietary Reference Intakes: Vitamins]).</ref>
| [[Paresthesia]]
| N/D
| Joint, skin and gastrointestinal complaints, dehydration, low mood, fatigue, and impaired metabolism.
|-
! [[Vitamin B6|Vitamin B<sub>6</sub>]]
| [[Pyridoxine]], [[pyridoxamine]], [[pyridoxal]]
| Water
| '''1.3–1.7 mg'''
| [[Anemia]]<ref name="GOVb6">[http://dietary-supplements.info.nih.gov/factsheets/vitaminb6.asp Vitamin and Mineral Supplement Fact Sheets Vitamin B<sub>6</sub>]</ref> [[peripheral neuropathy]].
| 100 mg
| Impairment of [[proprioception]], nerve damage (doses > 100 mg/day)
|-
! [[Biotin|Vitamin B<sub>7</sub>]]
| [[Biotin]]
| Water
| 30.0 µg
| [[Dermatitis]], [[enteritis]]
| N/D
| [[Hyperglycemia]] due to insulin deficiency, higher vitamin B6 and C requirements, and skin complaints.
|-
! [[Folic acid|Vitamin B<sub>9</sub>]]
| [[Folic acid]], [[folinic acid]]
| Water
| '''400 µg'''
| align="left"| Deficiency during pregnancy is associated with [[birth defects]], such as [[neural tube]] defects
| 1,000 µg
| Possible decrease in seizure threshold
|-
! [[Vitamin B12|Vitamin B<sub>12</sub>]]
| [[Cyanocobalamin]], [[hydroxycobalamin]], [[methylcobalamin]]
| Water
| '''2.4 µg'''
| [[Megaloblastic anemia]]<ref name="GOVb12">[http://dietary-supplements.info.nih.gov/factsheets/vitaminb12.asp Vitamin and Mineral Supplement Fact Sheets Vitamin B<sub>12</sub>] </ref>
| N/D
| No known toxicity<ref>http://dietary-supplements.info.nih.gov/factsheets/vitaminb12.asp</ref>
|-
! [[ويټامين C]]
| [[Ascorbic acid]]
| Water
| '''90.0 mg'''
| [[Scurvy]]
| 2,000 mg
| [[Vitamin C megadosage]]
|-
! style="whitespace:nowrap;"|[[Vitamin D]]
| [[Ergocalciferol]], [[cholecalciferol]]
| Fat
| 5.0 µg–10 µg<ref> Value represents suggested intake without adequate sunlight exposure (see [http://www.iom.edu/Object.File/Master/7/296/0.pdf Dietary Reference Intakes: Vitamins]).</ref>
| [[Rickets]] and [[Osteomalacia]]
| 50 µg
| [[Hypervitaminosis D]]
|-
! [[ويټامين E]]
| [[Tocopherol]]s, [[tocotrienol]]s
| Fat
| '''15.0 mg'''
|align="left"| Deficiency is very rare; mild [[hemolytic anemia]] in newborn infants.<ref name="Merck">[http://www.merck.com/mmhe/sec12/ch154/ch154a.html The Merck Manual: Nutritional Disorders: Vitamin Introduction] Please select specific vitamins from the list at the top of the page.</ref>
| 1,000 mg
| Increased congestive heart failure seen in one large randomized study.<ref>http://findarticles.com/p/articles/mi_m0ISW/is_262/ai_n13675725,</ref>
|-
! [[ويټامين K]]
| [[phylloquinone]], [[menaquinone]]s
| Fat
| 120 µg
| [[Bleeding diathesis]]
| N/D
| Increases coagulation in patients taking [[warfarin]].<ref>{{cite journal |author=Rohde LE, de Assis MC, Rabelo ER |title=Dietary vitamin K intake and anticoagulation in elderly patients |journal=Curr Opin Clin Nutr Metab Care |volume=10 |issue=1 |pages=1–5 |year=2007 |month=January |pmid=17143047 |doi=10.1097/MCO.0b013e328011c46c}}</ref>
|}
== In nutrition and diseases ==
[[دوتنه:Riboflavin.svg|thumb|250px|right|[[Riboflavin]] ([[Vitamin B]]<sub>2</sub>)]]
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.<ref>Dr. Leonid A. Gavrilov, [http://www.longevitymeme.org/articles/viewarticle.cfm?page=1&article_id=12 Pieces of the Puzzle: Aging Research Today and Tomorrow]</ref>
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]].<ref name="RDA"/>
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.
=== Deficiencies ===
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.<ref name="Merck"/> 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 [[disease]]s.
Because human bodies do not store most vitamins, humans must consume them regularly to avoid deficiency. Human bodily stores for different vitamins vary widely; vitamins A, D, and B<sub>12</sub> are stored in significant amounts in the human body, mainly in the [[liver]],<ref name="Merck"/> and an adult human's diet may be deficient in vitamins A and B<sub>12</sub> for many months before developing a deficiency condition. Vitamin B<sub>3</sub> is not stored in the human body in significant amounts, so stores may only last a couple of weeks.<ref name="GOVa"/><ref name="Merck"/>
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.<ref name="RDA"/><ref name="Merck"/>
Some evidence also suggests that there is a link between vitamin deficiency and mental disorders.<ref>Lakhan SE; Vieira KF. [http://www.nutritionj.com/content/7/1/2 Nutritional therapies for mental disorders]. ''Nutrition Journal'' 2008;7(2).</ref> There is some research suggesting appropriate levels of Vitamin D may reduce cancer risk. <ref>Office of Dietary Supplements, NIH [http://ods.od.nih.gov/factsheets/vitamind.asp] </ref>
=== Side effects and overdose ===
In large doses, some vitamins have documented [[Hypervitaminosis|side effects]] that tend to be more severe with a larger dosage. The likelihood of consuming too much of any vitamin from food is remote, but overdosing from vitamin supplementation does occur. At high enough dosages some vitamins cause side effects such as [[nausea]], [[diarrhea]], and [[vomit]]ing.<ref name=GOVa/><ref>Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. National Academy Press, Washington, DC, 2001.</ref>
When side effects emerge, recovery is often accomplished by reducing the dosage. The concentrations of vitamins an individual can tolerate vary widely, and appear to be related to age and state of health.<ref name="Healthier">[http://www.healthier-kids.com Healthier Kids] '''Section:''' What to take and how to take it.</ref> In the United States, overdose exposure to all formulations of vitamins was reported by 62,562 individuals in 2004 (nearly 80% of these exposures were in children under the age of 6), leading to 53 "major" life-threatening outcomes and 3 deaths<ref>[http://www.poison.org/prevent/documents/TESS%20Annual%20Report%202004.pdf 2004 Annual Report] of the American Association of Poison Control Centers Toxic Exposure Surveillance System.</ref>;a small number in comparison to the 19,250 people who died of unintentional poisoning of all kinds in the U.S. in the same year (2004).<ref>[http://www.cdc.gov/nchs/fastats/acc-inj.htm National Center for Health Statistics]</ref>
== Supplements ==
[[Dietary supplement]]s, often containing vitamins, are used to ensure that adequate amounts of nutrients are obtained on a daily basis, if optimal amounts of the nutrients cannot be obtained through a varied diet. Scientific evidence supporting the benefits of some dietary supplements is well established for certain health conditions, but others need further study.<ref name= Sup>[http://dietary-supplements.info.nih.gov/Health_Information/ODS_Frequently_Asked_Questions.aspx Use and Safety of Dietary Supplements] NIH office of Dietary Supplements.</ref> A [[meta-analysis]] 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 [[tobacco smoking|smokers]], for which it was already known that [[beta-carotene]] supplements can be harmful.<ref>{{cite journal |author=Bjelakovic G, et al. |title=Mortality in randomized trials of antioxidant supplements for primary and secondary prevention: systematic review and meta-analysis |journal=JAMA |volume=297 |issue=8 |pages=842–57 |year=2007 |pmid=17327526 | doi = 10.1001/jama.297.8.842}}. See also the [http://jama.ama-assn.org/cgi/content/extract/298/4/401-a letter] to [[Journal of the American Medical Association|JAMA]] by [[Philip Taylor]] and [[Sanford Dawsey]] and the [http://jama.ama-assn.org/cgi/content/extract/298/4/402 reply] by the authors of the original paper.</ref> Another study released in May 2009 found that antioxidants such as vitamins C and E may actually curb some benefits of exercise.<ref>http://www.nytimes.com/2009/05/12/health/research/12exer.html?em=&pagewanted=print</ref>
In the United States, advertising for dietary supplements is [[Health claims on food labels|required to include a disclaimer]] that the product is not intended to treat, diagnose, [[mitigate]], prevent, or cure disease, and that any health claims have not been evaluated by the [[Food and Drug Administration]].<ref name= Sup/> In some cases, dietary 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.<ref name= Sup/> Vitamin supplements may also contain levels of vitamins many times higher, and in different forms, than one may ingest through food.<ref name="Higdon"> Jane Higdon [http://lpi.oregonstate.edu/infocenter/vitamins/vitaminE/ Vitamin E recommendations at Linus Pauling Institute's Micronutrient Information Center]</ref>
Intake of excessive quantities can cause [[vitamin poisoning]], often due to overdose of [[Vitamin A]] and [[Vitamin D]]. (The most common poisoning with multinutrient supplement pills does not involve a vitamin, but is rather due to the mineral, [[iron]]). Due to toxicity, most common vitamins have recommended upper daily intake amounts.
Since 2005, suppliers have distinguished their products as either Medical Grade or Pharmaceutical Grade products. Both of these classifications indicate products that are manufactured to be easily absorbed by the body. Normal vitamin manufacturing is not regulated in the United States to the same standards as are medicinal pharmaceuticals, although U.S. vitamins which are manufactured for food consumption by humans or animals must be manufactured to [[Food Chemicals Codex]] (FCC), grade, commonly called "food grade".
=== Governmental regulation of vitamin supplements ===
Most countries place [[dietary supplement]]s in a special category under the general umbrella of ''foods'', not drugs. This necessitates that the manufacturer, and not the government, be responsible for ensuring that its dietary supplement products are safe before they are marketed. Unlike drug products, which must explicitly be proven safe and effective for their intended use before marketing, there are often no provisions to "approve" dietary supplements for safety or effectiveness before they reach the consumer. Also unlike drug products, manufacturers and distributors of dietary supplements are not generally required to report any claims of injuries or illnesses that may be related to the use of their products.<ref name="FDA">[http://www.fda.gov/Food/DietarySupplements/ConsumerInformation/ucm110417.htm Overview of Dietary Supplements]</ref><ref name="GOV">[http://www.cfsan.fda.gov/~dms/ds-ill.html Illnesses and Injuries Associated with the Use of Selected Dietary Supplements] U. S. [[Food and Drug Administration|FDA]] Center for Food Safety and Applied Nutrition</ref>
== 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.
The following table lists chemicals that had previously been classified as vitamins, as well as the earlier names of vitamins that later became part of the B-complex:
{|class="wikitable" style="margin: 1em auto 1em auto"
! پخواني نوم<ref name=Bennett>[http://www.lifeinyouryears.net/everyvitamin.pdf Every Vitamin Page] All Vitamins and Pseudo-Vitamins. Compiled by David Bennett.</ref><ref name =quiz>[http://www.pubquizhelp.34sp.com/sci/vitamin.html Vitamins and minerals - names and facts]</ref>
! كيمياوي نوم<ref name=Bennett/><ref name=quiz/>
! دنوم د بدلولو لامل<ref name=Bennett/>
|-
| [[B ويټامينونه|ويټامين B<sub>4</sub>]]
| [[Adenine]]
| DNA ميټابوليزم
|-
| [[B ويټامينونه|ويتامين B<sub>8</sub>]]
| [[Adenylic acid]]
| DNA metabolite
|-
| [[ويټامين F]]
| [[Essential fatty acid]]s
| Needed in large quantities (does<br /> not fit the definition of a vitamin).
|-
| [[ويټامين G]]
| [[Riboflavin]]
| Reclassified as [[B vitamins|ويټامين B<sub>2</sub>]]
|-
| [[ويټامين H]]
| [[Biotin]]
| Reclassified as [[B ويټامينونه|Vi>]]
|-
| [[ويټامين J]]
| [[Catechol]], [[Flavin group|Flavin]]
| Protein metabolite
|-
| ويټامين L<sub>1</sub><ref name=VitaminL> Michael W. Davidson (2004) [http://micro.magnet.fsu.edu/vitamins/pages/anthranilic.html Anthranilic Acid (Vitamin L)] [[Florida State University]]. Accessed 20-02-07</ref>
| [[Anthranilic acid]]
| Protein metabolite
|-
| ويټامين L<sub>2</sub><ref name=VitaminL/>
| [[Adenylthiomethylpentose]]
| RNA metabolite
|-
| [[ويټامين M]]
| [[Folic acid]]
| Reclassified as [[B vitamins|Vitamin B<sub>9</sub>]]
|-
| ويټامين O
| [[Carnitine]]
| Protein metabolite
|-
| [[ويټامين P]]
| [[Flavonoids]]
| No longer classified as a vitamin
|-
| [[ويټامين PP]]
| [[Niacin]]
| Reclassified as [[B vitamins|Vitamin B<sub>3</sub>]]
|-
| [[ويټامين U]]
| [[S-Methylmethionine]]
| Protein metabolite
|}
== See also ==
<div style="-moz-column-count:2; column-count:2;">
* [[Antioxidant]]
* [[Dietary supplement]]
* [[Dietetics]]
* [[Fat soluble vitamins]]
* [[Health freedom movement]]
* [[Illnesses related to poor nutrition]]
* [[Megavitamin therapy]]
* [[Nutrition]]
** [[Avitaminosis|Vitamin deficiency]]
** [[Dietary mineral]]s
** [[Essential amino acid]]s
** [[Essential nutrient]]s
** [[Nootropics]]
** [[Nutrient]]s
* [[Orthomolecular medicine]]
* [[Pharmacology]]
* [[Vitamin poisoning|Vitamin poisoning (overdose)]]
* [[Whole food supplements]]
</div>
== References ==
{{Reflist|2}}
== External links ==
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* [http://www.nal.usda.gov/fnic/dga/rda.pdf USDA RDA chart in PDF format]
* [http://www.hc-sc.gc.ca/fn-an/nutrition/reference/table/ref_vitam_tbl_e.html Health Canada Dietary Reference Intakes Reference Chart for Vitamins]
* [http://dietary-supplements.info.nih.gov/Health_Information/Vitamin_and_Mineral_Supplement_Fact_Sheets.aspx NIH Office of Dietary Supplements: Fact Sheets]
* [http://dietary-supplements.info.nih.gov/factsheets/dietarysupplements.asp NIH Office of Dietary Supplements. Dietary Supplements: Background Information]
{{ويټامين}}
{{Food chemistry}}
{{Nutritional pathology}}
{{Dietary supplement}}
[[وېشنيزه:ويټامينونه]]
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