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Vitamin D’s improtance for health in normal life

It is generally accepted (atleast in the west countries) that vitamin D deficiency is a worldwide health problem that affects not only musculoskeletal health but also a wide range of acute and chronic diseases. But, even then in South Asian countries like India and others, physicians or general public is not having full awarenes about the importance of Vit D and Vitamin profiling. Hardly doctors suggest somebody to go for Vitamin profile tests, and mostly people will not have idea that they do have very low Vitamins, specially Vitamin D which is so crucial for all critical diseases. Below is given a little details about Vitamin D, its importance and some mechanism related to.

Vitamin D deficiency has been recognized as a pandemic with a myriad of health consequences. Low vitamin D status has been associated with an increased risk of type 1 diabetes mellitus, cardiovascular disease, certain cancers, cognitive decline, depression, pregnancy complications, autoimmunity, allergy, and even frailty. Low prenatal and neonatal vitamin D status may also increase susceptibility to schizophrenia, type 1 diabetes, and multiple sclerosis (MS) in later life via specific target organ effects, including the immune system, or through epigenetic modification.

Vitamin D (D represents D2, D3, or both) is a secosterol produced endogenously in the skin from sun exposure or obtained from foods that naturally contain vitamin D, including cod liver oil and fatty fish (eg, salmon, mackerel, and tuna); UV-irradiated mushrooms; foods fortified with vitamin D; and supplements.

Despite the many important health benefits of vitamin D, there is controversy regarding the definition of vitamin D deficiency and what the vitamin D requirement should be. In addition, critical windows of exposure to adequate vitamin D levels during fetal maturation remain to be defined owing, in part, to the lack of well-designed controlled clinical trials with long-term follow-up.

Vitamin D (D represents D2, D3, or both) is a secosterol produced endogenously in the skin from sun exposure or obtained from foods that naturally contain vitamin D, including cod liver oil and fatty fish (eg, salmon, mackerel, and tuna); UV-irradiated mushrooms; foods fortified with vitamin D; and supplements.

During exposure to sunlight, 7-dehydrocholesterol (7-DHC) in the skin is converted to previtamin D3. The 7-DHC is present in all the layers of human skin. Approximately 65% of 7-DHC is found in the epidermis, and greater than 95% of the previtamin D3 that is produced is in the viable epidermis and, therefore, cannot be removed from the skin when it is washed. Once previtamin D3 is synthesized in the skin, it can undergo either a photoconversion to lumisterol, tachysterol, and 7-DHC or a heat-induced membrane-enhanced isomerization to vitamin D3. The cutaneous production of previtamin D3 is regulated. Solar photoproducts (tachysterol and lumisterol) inactive on calcium metabolism are produced at times of prolonged exposure to solar UVB radiation, thus preventing sun-induced vitamin D intoxication. Vitamin D3 is also sensitive to solar irradiation and is, thereby, inactivated to suprasterol 1 and 2 and to 5,6-trans-vitamin D3. Cutaneous vitamin D3 production is influenced by skin pigmentation, sunscreen use, time of day, season, latitude, altitude, and air pollution. An increase in the zenith angle of the sun during winter and early morning and late afternoon results in a longer path for the solar UVB photons to travel through the ozone layer, which efficiently absorbs them. This is the explanation for why above and below approximately 33° latitude little if any vitamin D3 is made in the skin during winter. This is also the explanation for why—whether being at the equator and in the far northern and southern regions of the world in summer, where the sun shines almost 24 hours a day—vitamin D3 synthesis occurs only between approximately 10 AM and 3 PM. Similarly, in urban areas, such as Los Angeles, California, and Mexico City, Mexico, where nitrogen dioxide and ozone levels are high, few vitamin D3-producing UVB photons reach the people living in these cities. Similarly, because glass absorbs all UVB radiation, no vitamin D3 is produced in the skin when the skin is exposed to sunlight that passes through glass.

The effect of vitamin D on fetal programming epigenetics and gene regulation could potentially explain why vitamin D has been reported to have such wide-ranging health benefits throughout life.

More details could be accessed from the link of a nicely written review article;

doi:  10.1016/j.mayocp.2013.05.011

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