Editing Vitamin (section)

===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 }}
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