Vitamin D The Sunshine “Vitamin”
History • Vitamin D was discovered as a cure for Rickets in the early 20th century. • It was first understood to only come from the skin of animals and was necessary for the body, and therefore it was named a vitamin. • However, further research showed that humans are able to manufacture significant quantities of it in their skin, this technically means that it is not a vitamin.
Rickets • A bone disease brought on by a Vitamin D deficiency. • Rickets causes weakening and softening of the bones in children. • It afflicted many children in the 18th and 19th century, killing many due to a lack of understanding of the disease. • The first cure for rickets came in the early 19th century in the form of cod liver oil; however, the reason why this worked was not know till the early 20th century.
Vitamin D • Vitamin D is a group of fat-soluble steroid molecules that are derived from the parent structure cholesterol. • Vitamin D is based on the cyclopentanoperhydrophenanthrene ring structure. • It is unique in that it is the only vitamin that is produced inside the body. • It is technically classified as a seco steroid hormone due to the fact that it is manufactured by the body and plays regulatory roles.
Vitamin D • There are two dominant forms of vitamin D, D2and D3. • Vitamin D, when either ingested or created in the skin, is inactive and must be hydroxylated two times in order to become hormonally active and useful to the body. • The first hydroxylation takes place in the liver where the number 25 carbon is hydroxylated. • The second hydroxylation takes place in the kidney where the number 1 carbon is hydroxylated.
Vitamin D3 • Also known as cholecalciferol. • Produced photochemically in the skin of animals and humans from the ultraviolet radiation of 7-dehydrocholesterol. • Regulation of production is controlled by an equilibrium; meaning that when the concentration of D3is high enough the ultraviolet radiation begins to break down the D3. 1,25- Dihydroxycholecalciferol 7-Dehydrocholesterol
Vitamin D3 • Vitamin D3 is produced in the epidermis of the skin. • The epidermis contains five strata. • From outer to inner: • Stratum Corneum • Stratum Lucidum • Stratum Granulosum • Stratum Spinosum • Stratum Basale • The stratum spinosum and basale is where the highest concentration of 7-dehydrocholesterol is found. • The melanin concentration in the epidermis is a factor that must be considered. UVB Melanin UVB 7-dehydrocholesterol
Vitamin D2 • Also known as ergocalciferol • Produced photochemically by the ultraviolet radiation of ergosterol in plants. • Functionally serves the same purpose as D3, however it is markedly less effective. 1,25- Dihydroxyergocalciferol Ergosterol
Comparison 1,25-Dihydroxycholecalciferol 1,25-Dihydroxyergocalciferol
Major Biological Role • Vitamin D is responsible for the regulation of calcium and phosphorus in the serum. • Vitamin D can increase or decrease the small intestine effectiveness of absorbing calcium and phosphorus. • This is made possible by the vitamin D receptor (VDR) which conformationally changes when bound to 1,25-dihydroxy vitamin D, which allows absorption of calcium and phosphorus in the small intestine so that bone mineralization can occur.
Minor/Recently Discovered biological roles • Recent studies have shown that vitamin D may be able to suppress some autoimmune diseases. • Also a recent study showed that vitamin D plays some role in neurotransmitter synthesis, however the exact role is not known yet.
Daily intake Still being debated…
Conclusion • Vitamin D is absolutely essential for natural function of the body. • We still do not understand all of the uses of vitamin D in the body and therefore further research must be conducted.
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