Vitamin D3, Research Paper Example

Introduction

Vitamin D3 is a very important seco steroid that has many important functions in the human body but is found very rarely in foods naturally.  It is mostly produced endogenously when ultraviolet rays from sunlight strike the skin to trigger vitamin D3 synthesis[1].  Investigation into Vitamin D3 began in the 17^th century when Dr. Daniel Whistler and Professor Francis Glisson provided the first scientific description of a vitamin D-deficiency disease, which was rickets[2]. Sir Edward Mellanby devised an experiment in 1919 that allowed him to establish the fact that the bone disease rickets was caused by a deficiency of a trace component present in the diet.  He wrote he believed that “the action of fats in rickets is due to a vitamin or accessory food factor which they contain, probably identical with the fat-soluble vitamin.[3]” Further studies in 1923 by Goldblatt and Soames and Steenbock and Black confirmed that the antirachitic factor was fat-soluble and due to the rapid rise in the science of nutrition, the substance became classified as a vitamin and is still known today as Vitamin D3[4].  However, a true Vitamin is a substance that is essential to bodily functions but which the body cannot manufacture and must be obtained through food.  Vitamin D3, however, is produced in the body by a photosynthetic reaction when the skin is exposed to sunlight[5].  The true chemical structure of Vitamin D was determined in the 1930’s by Professor A. Windaus at the University of Gottingen in Germany.  He established that Vitamin D3 was chemically a steroid, more specifically, a seco-steroid[6], and not a true vitamin as previously believed.

Structure and Property      

Vitamin D3 is a derivative of 7-dehydrocholesterol formed by ultraviolet rays breaking of the C9-C10 bond.  It differs from ergocalciferol in having a single bond between C22 and C23 and lacking a methyl group at C24[7].  It is known as Cholecalciferol and is officially classified as a steroid.  Vitamin D3 has a CAS Type 1 name of 9,10-Secocholesta-5,7,10(19)-trien-3-ol, (3beta,5Z,7E)-.

Vitamin D3 Synthesis

Vitamin D3 synthesis begins with the formation of vitamin D.  Vitamin D is photosynthesized in the skin when ultraviolet rays interact with 7-dehydrocholesterol[8].  Vitamin D is originally biologically inert and must go through two hydroxylation’s in the body for activation[9]. Once irradiated by the sun, the molecule moves to the liver where it is changed into 25-hydroxyvitamin D3, the major circulating form of the vitamin.  The molecule then moves to the kidneys, where it is converted into 1,25-dihydroxyvitamin D3.  This final product is the active form of the vitamin[10].  The activated form of Vitamin D3 is essential to calcium metabolism, which is why a deficiency in Vitamin D3 results in the bone disease of rickets.  In its activated form, D3 is a hormone since it is produced in the liver and is transported to the intestines where it is used to metabolize calcium.  Vitamin D is essential for preventing bone decay and promoting bone growth since it maintains the balance of calcium and phosphate concentrations in the body which are essential for normal mineralization of the bones[11].

Conclusion

Although Vitamin D is now found fortified in some foods such as milk and margarine, the main source of it remains the direct exposure of the skin to natural sunlight and ultraviolet light.  Recent evidence has revealed the importance of Vitamin D in preventing the risk of cancer.  It has been suggested that vitamin D deficiency may lead to different types of cancer including colon, breast, ovarian and prostate cancer[12].  The reason for vitamin D deficiency stems from the fact that many people do not receive adequate exposure to the sun each day.  If the photosynthetic effects from the sun to not occur, Vitamin D3 cannot be synthesized by the body.  In addition, many people use high protection sunscreen during the time when they are in the sun, again blocking the photosynthetic reaction[13].

In addition, there is evidence to suggest that vitamin D3 production is decreased with age.  The skin becomes less able to produce vitamin D3 as it ages, leading to vitamin D3 deficiency in the elderly[14].  This comes as no surprise since it is well known that bone density decreases with age and can lead to diseases such as osteoporosis.  Vitamin D deficiency in the elderly has been related to the deprivation of sunlight and to the avoidance of dairy products, but now it is also known that the skin becomes less able to photosynthesize the vitamin from the sun due to the ageing process.  The elderly must be exposed to more ultraviolet light than a younger person in order to synthesize the same amount of vitamin D3[15].

Vitamin D3 is an essential part of a healthy body and deficiency can cause a host of illnesses in people of all ages.  Even though it is possible to add this vitamin as a supplement to some foods, its most important source remains the sun.  This is why this vitamin is popularly called “The Sunshine Vitamin.

References

Garland, Cedric F., Garland, Frank C., Gorham, Edward D., Lipkin, Martin, Newmark, Harold,

Mohr, Scarif B., Holick, Michael F. “The Role of Vitamin D in Cancer Prevention.” American Journal of Public Health.  Feb. 2006 96(2): 252 http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1470481/?tool=pmcentrez

MacLaughlin, Julia, Holick, Michael F.  “Aging Decreases the Capacity of Human Skin to Produce Vitamin D3.” Journal of Clinical Investigation 76 October 1985 1536-1538. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC424123/pdf/jcinvest00124-0254.pdf

National Academy of Sciences. “Unraveling the Enigma of Vitamin D.” Beyond Discovery Web. Retrieved 9 May 2010 from http://www.beyonddiscovery.org/content/view.txt.asp?a=414

National Institute of Health. “Dietary Supplement Fact Sheet: Vitamin D” Office of Dietary Supplements Web. Retrieved 9 May 2010 from http://ods.od.nih.gov/factsheets/vitamind.asp

National Library of Medicine “MeSH Descriptor Data.” Web. Retrieved 9 May 2010 from http://www.nlm.nih.gov/cgi/mesh/2009/MB_cgi?mode=&term=CHOLECALCIFEROLS

University of California, Riverside. “History of Vitamin D.” Vitamin D Workshop Web. Retrieved 9 May 2010 from http://vitamind.ucr.edu/history.html

[1] National Institute of Health, 2010

[2] University of California, 2010

[3] University of California, 2010

[4] University of California, 2010

[5] National Academy of Sciences, 2010

[6]  University of California, 2010

[7] National Library of Medicine, 2010.

[8] National Academy of Sciences, 2010.

[9] National Institute of Heatlh, 2010.

[10] National Academy of Sciences, 2010.

[11] National Institute of Health, 2010.

[12] Garland, Garland, Gorham, Lipkin, Newmark, Mohr, Holick, 2006.

[13] Garland, Garland, Gorham, Lipkin, Newmark, Mohr, Holick, 2006.

[14] MacLaughlin and Holick, 1985.

[15] MacLaughlin and Holick, 1985.