Structural Biochemistry/Chemistry of important organic molecules in Biochemistry/Vitamin D

Introduction

Most of the vitamins are known to act as coenzymes. However, Vitamin D, also known as calciferol, do not behave as coenzymes. Instead, Vitamin D are known to regulate calcium and phosphate metabolisms. Through recent research, Vitamin D are known for preventing different cancers and cardiovascular disease, protecting against diabetes, and enhancing the ability of muscle works. ^[1]

Naturally, the best sources for vitamin D can be found in fatty fish like salmon and tuna and in fish liver oils. Smaller amounts of vitamin D can also be found in beef liver, cheese, and egg yolks. Vitamin D can also be taken in the form of supplements, either in the form D₂ or D₃. Most of people are attain their vitamin D through sunlight exposure. The UV-B radiation of sunlight penetrates the skin and converts 7-dehydrocholesterol to previtamin D3 which then becomes vitamin D₃.

Health effects of supplements

Up until today, the effects of vitamin D supplementation on health are uncertain. A United States Institute of Medicine (IOM) report states that outcomes that are related to disease such as cancer or diabetes could not be linked reliably with calcium or vitamin D intake. However, some researchers claimed that the IOM made a mistake when calculating the blood level of vitamin D associated with bone health. In return, the IOM members said that they used a standard procedure for dietary recommendations and that the result is just based on what they had in their data. Basically, many researchers use large scale of clinical trials to do research on vitamin D supplements.

Bone Health

Osteomalacia also known as rickets (when happen to children) are caused by vitamin D deficiency. Low serum vitamin D levels have been associated with falls, and low bone mineral density. The United States Preventive Services Task Force in the year of 2012 issued a draft statement conveying that there is not enough evidence to indicate that healthy postmenopausal women should use supplemental doses of calcium or vitamin D to prevent any fractures.

However, there are also other studies that show that any supplementation containing vitamin D and calcium may improve bone mineral density. Supplementation containing vitamin D may also decrease the risk of falls and fractures in only certain groups of people and not all. Further studies, even proved that elders in the age of 65 may take these supplements and decrease the risk of fractures. However, there is not much evidence that can prove this actually works. In the end, it appears that without a good amount of calcium, the amount of vitamin D that a person consume is not enough to benefit the bone health.

Mortality

Low blood levels of vitamin D are related with increased mortality. Elderly women that are giving supplementary vitamin D3 seems to decrease the risk of death. However, there are vitamins that are not seen effective. One such vitamin is vitamin D2, and other vitamins are like alfacalcidol and calcitriol. It is important to note that consuming vitamin D is good for the health, but an excess and a deficiency in vitamin D appear to cause abnormal functioning and premature aging.

Cancer

Taking supplements containing vitamin D does not appear to help people with prostate cancer. However, there some cancers that are related to low vitamin D levels and with worse outcomes in other cancers. As of today, there is not enough evidence to support supplementation in those with cancer.

Pregnancy

It is actually good for pregnant women to take a good amount of vitamin D because it will give positive immune effects. However, there are many women who are pregnant that does not take the recommended dose of vitamin D and this will definitely create a negative impact on the mother and her baby in the stomach.

Multiple Sclerosis

Multiple sclerosis is related to low vitamin D. Although there are uncertainties, many supplementation that contains vitamin D may have a protective effect.

The reason why vitamin D deficiency is thought to case multiple sclerosis is due to the following reasons:

MS often increases with increasing latitude, which is strongly inversely correlated with duration and intensity of UVB from vitamin D concentrations and the sunlight.
At higher latitudes in populations with high consumption of vitamin D (rich fatty fish), the prevalence of MS are lower than expected.
With migration from high to low latitudes, MS risk decreases.

Since the year 2011, Vitamin D3 is tested to be as a treatment of Multiple Sclerosis.

Synthesis

Vitamin D is synthesized from 7-dehydrocholesterol to calcitriol (1,25-dihydroxycholecalciferol) in three different steps. The first process in this synthesis is by utilizing ultraviolet light to photolyze 7-dehydrocholesterol to previtamin D₃. The second process occurs immediately when the previtamin D₃ isomerizes to create vitamin D₃, also known as Cholecalciferol. The last process occurs when vitamin D₃ (Cholecalciferol) goes through the process of hydroxylation reaction to form calcitriol (1,25-dihydroxycholecalciferol). ^[2] The images shown below indicate the process of synthesizing Vitamin D in three different steps:

7-Dehydrocholesterol is formed by enzymatic oxidation of cholesterol and has a conjugated diene unit in its B ring. 7-Dehydrocholesterol is present in the tissues of the skin, where it is transformed to vitamin D3 by a sunlight-induced photochemical reaction. Vitamin D 3 is a key compound in the process by which Ca²⁺ is absorbed from the intestine. Low levels of vitamin D 3 lead to Ca²⁺ concentrations in the body that are insuffi cient to support proper bone growth, resulting in the bone disease called rickets.

7-Dehydrocholesterol is transformed to vitamin D 3 by a sunlight-induced photochemical reaction

Deficiency of Vitamin D

Deficiency of Vitamin D may cause severe damages to both children and adults. Children should be aware of the disease known as rickets which is mainly caused by Vitamin D deficiency. The symptoms of rickets are deformation of skeletal bones which affects in impaired growth. Adults should be aware of the disease known as osteomalacia. Symptoms for osteomalacia is bending of bones due to its weakness. A primary way to escape from Vitamin D deficiency is through fortified foods. Milk is an excellent way to consume an acceptable portion of Vitamin D for our daily lives. ^[3]

People at risk of not getting enough vitamin D include:

breastfed infants - their vitamin D intake directly corresponds to their mother's vitamin D levels
older adults - As they age their skin decreases in its efficiency to synthesize vitamin D. Also can be caused because they are more likely to stay indoors
people with limited sun exposure - As UV rays from the sun are the main source for vitamin D, limiting the sun exposure can drastically decrease the vitamin D intake.
dark-skinned people - The greater amounts of melanin reduces the skin's ability to produce vitamin D from sunlight.
obese people - Those who are obese may need higher amounts of vitamin D than those who are not obese.

References

↑ Berg, Jeremy M., John L. Tymoczko, and Lubert Stryer. Biochemistry. 7th ed. New York: W.H. Freeman, 2012. Print.
↑ Berg, Jeremy M., John L. Tymoczko, and Lubert Stryer. Biochemistry. 7th ed. New York: W.H. Freeman, 2012. Print.
↑ Berg, Jeremy M., John L. Tymoczko, and Lubert Stryer. Biochemistry. 7th ed. New York: W.H. Freeman, 2012. Print.

4. Carey, Francis A. "24." Organic Chemistry. 8th ed. Boston: McGraw-Hill, 2003. 1101. Print.

http://en.wikipedia.org/wiki/Vitamin_D

"Dietary Supplement Fact Sheet:Vitamin D". Office of Dietary Supplements. http://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/

[1] Berg, Jeremy M., John L. Tymoczko, and Lubert Stryer. Biochemistry. 7th ed. New York: W.H. Freeman, 2012. Print.

[2] Berg, Jeremy M., John L. Tymoczko, and Lubert Stryer. Biochemistry. 7th ed. New York: W.H. Freeman, 2012. Print.

[3] Berg, Jeremy M., John L. Tymoczko, and Lubert Stryer. Biochemistry. 7th ed. New York: W.H. Freeman, 2012. Print.

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