ENVIRONMENTAL-FACTORS THAT INFLUENCE THE CUTANEOUS PRODUCTION OF VITAMIN-D
ENVIRONMENTAL-FACTORS THAT INFLUENCE THE CUTANEOUS PRODUCTION OF VITAMIN-D
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DOI：
10.1093/ajcn/61.3.638s
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发表时间：
1995-03-01
影响因子：
7.1
通讯作者：
HOLICK, MF
中科院分区：
文献类型：
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作者：
HOLICK, MF
包括人类在内的所有脊椎动物，每天大部分的维生素D需求都来自偶然的阳光照射。在暴露于阳光期间，太阳紫外线B光子（290-315 nm）穿透皮肤，在皮肤中它们导致7-脱氢胆固醇光解为前胆钙化醇。一旦形成，前胆钙化醇经历其双键的热诱导重排以形成胆钙化醇。皮肤色素沉着的增加、老化和防晒霜的局部应用减少了胆钙化醇的皮肤产生。纬度、季节和一天中的时间以及大气中的臭氧污染影响到达地球表面的太阳紫外线B光子的数量，从而改变胆钙化醇的皮肤产生。在波士顿，从11月到2月暴露在阳光下不会在皮肤中产生任何显着量的胆钙化醇。由于窗玻璃吸收紫外线B辐射，因此阳光透过玻璃窗照射不会导致任何胆钙化醇的产生。现在人们认识到，维生素D不足和维生素D缺乏症在老年人中很常见，特别是那些体弱且不暴露在阳光下或生活在冬季无法为他们提供阳光介导的胆钙化醇的纬度的人。维生素D不足和缺乏会加剧骨质疏松症，引起骨软化，并增加骨折的风险。维生素D不足和缺乏可以通过鼓励负责任地暴露在阳光下和/或食用含有10 μ g（400 IU）维生素D的多种维生素片剂来预防。
All vertebrates, including humans, obtain most of their daily vitamin D requirement from casual exposure to sunlight. During exposure to sunlight, the solar ultraviolet B photons (290-315 nm) penetrate into the skin where they cause the photolysis of 7-dehydrocholesterol to precholecalciferol. Once formed, precholecalciferol undergoes a thermally induced rearrangement of its double bonds to form cholecalciferol. An increase in skin pigmentation, aging, and the topical application of a sunscreen diminishes the cutaneous production of cholecalciferol. Latitude, season, and time of day as well as ozone pollution in the atmosphere influence the number of solar ultraviolet B photons that reach the earth's surface, and thereby, alter the cutaneous production of cholecalciferol. In Boston, exposure to sunlight during the months of November through February will not produce any significant amounts of cholecalciferol in the skin. Because windowpane glass absorbs ultraviolet B radiation, exposure of sunlight through glass windows will not result in any production of cholecalciferol. It is now recognized that vitamin D insufficiency and vitamin D deficiency are common in elderly people, especially in those who are infirm and not exposed to sunlight or who live at latitudes that do not provide them with sunlight-mediated cholecalciferol during the winter months. Vitamin D insufficiency and deficiency exacerbate osteoporosis, cause osteomalacia, and increase the risk of skeletal fractures. Vitamin D insufficiency and deficiency can be prevented by encouraging responsible exposure to sunlight and/or consumption of a multivitamin tablet that contains 10 mu g (400 IU) vitamin D.