In this article, I want us to discuss how does the sun provide us with Vitamin D. Vitamin D helps to regulate the amount of calcium and phosphate in the body. These nutrients are needed to keep bones, teeth and muscles healthy. Lack of vitamin D can lead to bone deformities. It is a myth that sun provides us vitamin D or vitamin D is present in sunlight. As such, most people stand in the sun early in the morning just to absorb vitamin D from early morning sunset.
The fact is vitamin D is synthesized in plants, animals and humans in presence of sunlight.
There are two types of vitamin D namely, Vitamin D2 (Ergocalciferol) found in plants including ergot and mushrooms and vitamin D3 (Cholecalciferol) present in animals.
Vitamin D2 (Ergocalciferol) and Vitamin D3 (Cholecalciferol) are synthesized in presence of ultraviolet light (UV) of sunlight as given below.
In plants, the ergo-calciferol (vitamin D2) is derived from UV irradiation of ergosterol (a kind of sterol present in plants).
In animals and humans, when skin is exposed to sunlight, chole-calciferol (vitamin D3) is produced in skin by UV irradiation of 7-dehydro-cholesterol (a kind of cholesterol present in animals and humans).
Sunlight triggers the first of three chemical reactions that converts an inactive compound in the skin into active vitamin D. Ultraviolet B rays from the sun convert a natural vitamin D precursor present in your skin, 7-dehydrocholesterol, into vitamin D3. This travels to the liver where the addition of oxygen and hydrogen to vitamin D3 changes it into 25-hydroxyvitamin D. Doctors test for this intermediate and still inactive form of vitamin D in blood to determine your vitamin D status. Final activation of 25-hydroxyvitamin D takes place in the kidneys, where more oxygen and hydrogen molecules attach to 25-hydroxyvitamin D and convert it into its active form known as 1,25 dihydroxy vitamin D, or calcitriol.

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