Editing Vitamin (section)

== Intake ==

===Sources===
For 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 (nutrient)|niacin]] is synthesized from the [[amino acid]] [[tryptophan]].<ref name="DRI-Niacin">{{cite book|title=Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline|last1=Institute of Medicine|publisher=The National Academies Press|year=1998|isbn=978-0-309-06554-2|location=Washington, DC|pages=123–149|chapter=Niacin|access-date=29 August 2018|chapter-url=https://www.nap.edu/read/6015/chapter/8|author1-link=Institute of Medicine}}</ref> Vitamin C can be synthesized by some species but not by others. [[Vitamin B12|Vitamin B<sub>12</sub>]] 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<sub>1</sub>, B<sub>2</sub> and B<sub>12</sub>.<ref name="FoodFortif" />

===Deficient intake===
{{See also|Vitamin deficiency}}

The [[human body|body's]] stores for different vitamins vary widely; vitamins A, D, and B<sub>12</sub> are stored in significant amounts, mainly in the [[liver]],<ref name="Merck" /> and an adult's diet may be deficient in vitamins A and D for many months and B<sub>12</sub> in some cases for years, before developing a deficiency condition. However, vitamin B<sub>3</sub> (niacin and niacinamide) is not stored in significant amounts, so stores may last only a couple of weeks.<ref name="GOVa" /><ref name="Merck" /> For vitamin C, the first symptoms of scurvy in experimental studies of complete vitamin C deprivation in humans have varied widely, from a month to more than six months, depending on previous dietary history that determined body stores.<ref>{{cite journal | vauthors = Pemberton J | title = Medical experiments carried out in Sheffield on conscientious objectors to military service during the 1939–45 war | journal = International Journal of Epidemiology | volume = 35 | issue = 3 | pages = 556–558 | date = June 2006 | pmid = 16510534 | doi = 10.1093/ije/dyl020 | doi-access = free }}</ref>

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, but may be consuming less than the recommended amounts; a national food and supplement survey conducted in the US over 2003–2006 reported that over 90% of individuals who did not consume vitamin supplements were found to have inadequate levels of some of the essential vitamins, notably vitamins D and E.<ref name=":03">{{cite journal | vauthors = Bailey RL, Fulgoni VL, Keast DR, Dwyer JT | title = Examination of vitamin intakes among US adults by dietary supplement use | journal = Journal of the Academy of Nutrition and Dietetics | volume = 112 | issue = 5 | pages = 657–663.e4 | date = May 2012 | pmid = 22709770 | pmc = 3593649 | doi = 10.1016/j.jand.2012.01.026 }}</ref>

Well-researched human vitamin deficiencies involve thiamine (beriberi), niacin ([[pellagra]]),<ref name="Wendt" /> vitamin C (scurvy), folate (neural tube defects) and vitamin D (rickets).<ref name="Price">{{cite book|url=https://books.google.com/books?id=IPcVBAAAQBAJ&pg=PR96|title=Vitamania: Our obsessive quest for nutritional perfection| vauthors = Price C |date=2015|publisher=Penguin Press|isbn=978-1594205040|name-list-style=vanc}}</ref> 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.<ref name="Merck" /> In addition to these classical vitamin deficiency diseases, some evidence has also suggested links between vitamin deficiency and a number of different disorders.<ref>{{cite journal | vauthors = Lakhan SE, Vieira KF | title = Nutritional therapies for mental disorders | journal = Nutrition Journal | volume = 7 | pages = 2 | date = January 2008 | pmid = 18208598 | pmc = 2248201 | doi = 10.1186/1475-2891-7-2 | doi-access = free }}</ref><ref>{{cite journal | vauthors = Boy E, Mannar V, Pandav C, de Benoist B, Viteri F, Fontaine O, Hotz C | title = Achievements, challenges, and promising new approaches in vitamin and mineral deficiency control | journal = Nutrition Reviews | volume = 67 | issue = Suppl 1 | pages = S24–S30 | date = May 2009 | pmid = 19453674 | doi = 10.1111/j.1753-4887.2009.00155.x }}
</ref>

===Excess intake===
{{See also|Hypervitaminosis}}

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).<ref name="DRITable" /><ref name="EFSA" /><ref name="JapanDRI" /> 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 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.<ref>{{cite journal | vauthors = Gummin DD, Mowry JB, Spyker DA, Brooks DE, Fraser MO, Banner W | title = 2016 Annual Report of the American Association of Poison Control Centers' National Poison Data System (NPDS): 34th Annual Report | journal = Clinical Toxicology | volume = 55 | issue = 10 | pages = 1072–1252 | date = December 2017 | pmid = 29185815 | doi = 10.1080/15563650.2017.1388087 | s2cid = 28547821 | doi-access = free }}</ref> 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.<ref name=":03"/>

===Effects of cooking===
The [[USDA]] has conducted extensive studies on the percentage losses of various nutrients from food types and cooking methods.<ref>{{Cite web|url=http://www.ars.usda.gov/SP2UserFiles/Place/80400525/Data/retn/retn06.pdf|title = USDA Table of Nutrient Retention Factors, Release 6|date = Dec 2007|website = USDA|publisher = USDA.}}</ref> Some vitamins may become more "bio-available" – that is, usable by the body – when foods are cooked.<ref>[http://www.beyondveg.com/tu-j-l/raw-cooked/raw-cooked-2f.shtml Comparison of Vitamin Levels in Raw Foods vs. Cooked Foods]. Beyondveg.com. Retrieved on 3 August 2013.</ref> 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 the water when a vegetable is boiled, and are then lost when the water is discarded.<ref>[http://www.beyondveg.com/tu-j-l/raw-cooked/raw-cooked-2e.shtml Effects of Cooking on Vitamins (Table)]. Beyondveg.com. Retrieved on 3 August 2013.</ref>

{| class="wikitable sortable" border="1" |-
! rowspan="2" |Vitamin
! colspan="4" |'''Is substance susceptible to losses under given condition?'''
|-
!Soluble in Water
!Air Exposure
!Light Exposure
!Heat Exposure
|-
|Vitamin A
| no
| partially
| partially
| relatively stable
|-
|Vitamin C
| very unstable
| yes
| no
| no
|-
| Vitamin D
| no
| no
| no
| no
|-
| Vitamin E
| no
| yes
| yes
| no
|-
|Vitamin K
| no
| no
| yes
| no
|-
|Thiamine (B<sub>1</sub>)
| highly
| no
| ?
| > 100&nbsp;°C
|-
|Riboflavin (B<sub>2</sub>)
| slightly
| no
| in solution
| no
|-
|Niacin (B<sub>3</sub>)
| yes
| no
| no
| no
|-
|Pantothenic Acid (B<sub>5</sub>)
| quite stable
| no
| no
| yes
|-
|Vitamin B<sub>6</sub>
| yes
| ?
| yes
| < 160&nbsp;°C
|-
|Biotin (B<sub>7</sub>)
| somewhat
| ?
| ?
| no
|-
|Folic Acid (B<sub>9</sub>)
| yes
| ?
| when dry
| at high temp
|-
|Cobalamin (B<sub>12</sub>)
| yes
| ?
| yes
| no
|}