Vitamin d is a fat-soluble vitamin, also seen as an effect on calcium and phosphate metabolism before Hormone, which is closely related to the sun, so called sunshine vitamin。D is a family of Vitamin A, the same as B, C, d ring structure, but the structure of the side chain of a different generic term for a class of composites, A, B, C, d steroid ring cyclopentadienyl derived from ethylenically hydrogen phenanthrene ring structure, present vitamin d known there are at least 10 species, but the most important is vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol)。
Vitamin D2 is ergosterol ultraviolet irradiation plants produced less presence in nature。
Vitamin D3 by the most senior animal epidermis and dermis contained 7-dehydrocholesterol by ultraviolet light (wavelength 265?228 nm) irradiation transition from。Vitamin D3 is the highest metabolic rate of a biological active form of vitamin d。Later mentioned mainly refers to vitamin d vitamin D3 Vitamin D3 (cholecalciferol) is mainly synthesized by the body itself, contain a human skin cholesterol, after sunlight, vitamin D3 becomes。So, if the child can fully accept the skin more than 4-6 hours of direct sunlight, then own synthesis of vitamin D3, it can basically meet。But skin cancer caused by ultraviolet radiation rise, under the impact of air pollution, local weather changes, people receiving countries sunshine time are on the decline, and many countries clearly defined to limit the acceptance of sunshine time, so worldwide vitamin d deficiency showed a wide range of phenomena。
In addition, vitamin D3 can also come from animal foods such as liver, especially refined seafood from the fish liver of cod liver oil。
In addition to the presence of vitamin D3 in addition to a small number of animal food, mainly form after ultraviolet irradiation of 7 – dehydrocholesterol through the skin, and the 7-dehydrocholesterol cholesterol level is generated by the transformation of cholesterol, so some people call it the sun vitamin。
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