[来源:shaklee corporation，丁香园] 2022-12-12 10:06:40
多年前，科学家就发现晒太阳可以补充维生素d。当人体皮肤表层的7-脱氢胆固醇遇到阳光里的紫外线后，就会生成这种维生素。人体内源性维生素d约80%在皮肤表皮合成，仅20%从食物中摄取，所以维生素d也被称为"阳光维生素"。
the connection between sunlight and bone health was made over 200 years ago when a polish doctor treated inner city children with rickets (or soft bones) by taking them to the countryside for the summer months. in fact, vitamin d promotes heart, metabolic, and immune system health in addition to supporting bone health.
200多年前，当一位波兰医生带着患有佝偻病（或软骨头）的城市儿童去乡下避暑时，发现了阳光与骨骼健康之间的联系。事实上，维生素d除了有益骨骼健康外，还对心脏、新陈代谢和免疫系统健康有益。
vitamin d is absorbed into our bloodstream and converted to the active form (a secosteroidal hormone) and a storage form (25-hydroxyvitamin d) – it functions more like a hormone than a vitamin. so, it is no surprise that having sufficient levels of vitamin d is so important for a broad array of health effects.
维生素d被血液吸收，并转化为活性形式（一种开环甾体激素）和储存形式（25-羟基维生素d）——其功能更像是一种激素而不是维生素。因此，充足的维生素d对健康有着重要影响。
potential benefits associated with vitamin d include:
维生素d的潜在健康益处包括：
aids in calcium absorption for maintaining strong bones and teeth
促进钙吸收，保持骨骼和牙齿强健
helps support healthy heart and immune function
有益心脏健康和增强免疫功能
facilitates healthy cell development
促进健康的细胞发育
值得注意的是，只有裸露的皮肤接受太阳光照射的时候才能产生维生素d。因此，冬天更需要多晒太阳，才能补充充足的维生素d。
晒太阳的时间需要多久？
冬春季，将面部和双上臂暴露于阳光下 10～30 分钟，夏季由于紫外线较强，裸露部位较多，接受太阳直射 5～10 分钟，每周 2～3 次就能让身体产生足够的维生素 d。绝大多数人每天在阳光下晒 10 至 20 分钟即可。
隔着玻璃晒太阳有效吗？
隔着玻璃晒太阳会大大降低效果，因为中波紫外线 uvb 的穿透性比较差。在家中隔着玻璃晒太阳几乎是无效的，因为中波紫外线的透过率会大幅度降低，从而影响人体合成维生素 d。晒太阳的最佳地点是户外，因各种原因必须在室内晒太阳，也一定要打开窗子，让阳光直接与皮肤接触。
"vitamin d is produced when sunlight touches our skin, and very few foods in nature contain vitamin d, with fortified foods – primarily cow's milk – being responsible for most of the vitamin d in the american diet," said jamie mcmanus, shaklee's chair of medical affairs. "as daylight savings time ends, we have less opportunity to absorb vitamin d through sunlight. therefore, people should supplement their vitamin d intake, especially during winter."
美国营养品公司嘉康利医学事务主席杰米·麦克马纳斯称：“当阳光照射皮肤时，人体就会产生维生素d，自然界中含有维生素d的食物较少，而牛奶是美国人饮食中维生素d的主要来源。随着夏令时间结束，通过阳光吸收维生素d的机会减少。因此，人们应该补充维生素d摄入量，尤其是在冬季。”
[责编:田梦瑶]
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