Vitamin D

Vitamin D
Drug class
Cholecalciferol (D3)
Class identifiers
SynonymsCalciferols
UseRickets, osteoporosis, osteomalacia, vitamin D deficiency
ATC codeA11CC
Biological targetvitamin D receptor
Clinical data
Drugs.comMedFacts Natural Products
External links
MeSHD014807
Legal status
In Wikidata

Vitamin D is a group of structurally related, fat-soluble compounds responsible for increasing intestinal absorption of calcium, magnesium, and phosphate, along with numerous other biological functions.[1][2] In humans, the most important compounds within this group are vitamin D3 (cholecalciferol) and vitamin D2 (ergocalciferol).[2][3]

Unlike the other twelve vitamins, vitamin D is only conditionally essential, as with adequate skin exposure to the ultraviolet B (UVB) radiation component of sunlight there is synthesis of cholecalciferol in the lower layers of the skin's epidermis. Vitamin D can also be obtained through diet, food fortification and dietary supplements.[2] For most people, skin synthesis contributes more than dietary sources.[4] In the U.S., cow's milk and plant-based milk substitutes are fortified with vitamin D3, as are many breakfast cereals. Government dietary recommendations typically assume that all of a person's vitamin D is taken by mouth, given the potential for insufficient sunlight exposure due to urban living, cultural choices for the amount of clothing worn when outdoors, and use of sunscreen because of concerns about safe levels of sunlight exposure, including the risk of skin cancer.[2][5]: 362–394 

Cholecalciferol is converted in the liver to calcifediol (also known as calcidiol or 25-hydroxycholecalciferol), while ergocalciferol is converted to ercalcidiol (25-hydroxyergocalciferol). These two vitamin D metabolites, collectively referred to as 25-hydroxyvitamin D or 25(OH)D, are measured in serum to assess a person's vitamin D status. Calcifediol is further hydroxylated by the kidneys and certain immune cells to form calcitriol (1,25-dihydroxycholecalciferol; 1,25(OH)2D), the biologically active form of vitamin D.[3] Calcitriol attaches to vitamin D receptors, which are nuclear receptors found in various tissues throughout the body.

Vitamin D is essential for increasing bone density, therefore causing healthy growth spurts.[6]

The discovery of the vitamin in 1922 was due to an effort to identify the dietary deficiency in children with rickets.[7][8] Adolf Windaus received the Nobel Prize in Chemistry in 1928 for his work on the constitution of sterols and their connection with vitamins.[9] Present day, government food fortification programs in some countries and recommendations to consume vitamin D supplements are intended to prevent or treat vitamin D deficiency rickets and osteomalacia. There are many other health conditions linked to vitamin D deficiency. However, the evidence for the health benefits of vitamin D supplementation in individuals who are already vitamin D sufficient is unproven.[2][10][11][12]

  1. ^ "Vitamin D". Micronutrient Information Center, Linus Pauling Institute, Oregon State University, Corvallis. 11 February 2021. Archived from the original on 8 April 2015. Retrieved 14 March 2022.
  2. ^ a b c d e "Vitamin D: Fact Sheet for Health Professionals". Office of Dietary Supplements, US National Institutes of Health. 26 July 2024. Archived from the original on 9 April 2021. Retrieved 20 January 2025.
  3. ^ a b Bikle DD (March 2014). "Vitamin D metabolism, mechanism of action, and clinical applications". Chemistry & Biology. 21 (3): 319–329. doi:10.1016/j.chembiol.2013.12.016. PMC 3968073. PMID 24529992.
  4. ^ Cite error: The named reference Giustina2024 was invoked but never defined (see the help page).
  5. ^ Cite error: The named reference Ross_2011 was invoked but never defined (see the help page).
  6. ^ "Vitamins to Help You Reach Your Full Growth Potential". Livestrong.com. Retrieved 18 June 2025.
  7. ^ Wolf G (June 2004). "The discovery of vitamin D: the contribution of Adolf Windaus". The Journal of Nutrition. 134 (6): 1299–302. doi:10.1093/jn/134.6.1299. PMID 15173387.
  8. ^ Deluca HF (January 2014). "History of the discovery of vitamin D and its active metabolites". BoneKEy Reports. 3: 479. doi:10.1038/bonekey.2013.213. PMC 3899558. PMID 24466410.
  9. ^ Cite error: The named reference Nobelprize was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference reid was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference Futil2014 was invoked but never defined (see the help page).
  12. ^ "The Lancet Diabetes & Endocrinology: Vitamin D supplementation in adults does not prevent fractures, falls or improve bone mineral density". EurekAlert!. Archived from the original on 24 March 2022. Retrieved 23 February 2022. The authors conclude that there is therefore little reason to use vitamin D supplements to maintain or improve musculoskeletal health, except for the prevention of rare conditions such as rickets and osteomalacia in high-risk groups, which can be caused by vitamin D deficiency after long lack of exposure to sunshine.
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