Vitamin D and skin physiology: A D-lightful story
Vitamin D and skin physiology: A D-lightful story
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DOI：
10.1359/jbmr.07s211
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发表时间：
2007-12-01
影响因子：
6.2
通讯作者：
Sauter, Edward
中科院分区：
文献类型：
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作者：
Holick, Michael F.;Chen, Tai C.;Sauter, Edward
在整个进化过程中，阳光照射和皮肤中维生素 D-3 的光合作用对于陆地脊椎动物的进化至关重要。在暴露于阳光下时，能量为 290-315 nm 的太阳 UVB 光子被皮肤中的 7-脱氢胆固醇吸收并转化为前维生素 D-3。前维生素 D-3 在质膜内快速转化为维生素 D-3。过度暴露在阳光下不会导致维生素 D 中毒，因为前维生素 D-3 和维生素 D-3 都会被光解成几种非钙血光产物。在纬度高于 35 度的冬季，皮肤中产生的前维生素 D3（如果有的话）也很少。海拔高度对维生素 D-3 的产生也有显着影响。 11 月北纬 27 度时，阿格拉（169 英寸）和加德满都（1400 英寸）检测到的维生素 D-3 前合成量非常少（接近 0.5%）。在海拔 3400 米附近和珠穆朗玛峰大本营（5300 英寸）处，前维生素 D-3 的产量分别增加了 2 倍和 4 倍。皮肤色素沉着增加、涂抹防晒霜、衰老和着装会对皮肤中前维生素 D-3 的产生产生巨大影响。据估计，穿着泳衣接触 1 个最小红斑剂量 (MED) 相当于摄入 10,000 至 25,000 IU 的维生素 D-2。 25-羟基维生素 D [25(OH)D] 循环水平的季节性变化充分证明了阳光对于满足大多数人维生素 D 需求的重要性。维生素 D 缺乏 [即 25(OH)D < 20 ng/ml] 在全世界儿童和成人中都很常见。暴露在产生 UVB 辐射的灯下是在皮肤中产生维生素 D-3 的极好来源，对于患有脂肪吸收不良综合征的患者尤其有效。全球维生素 D 缺乏的主要原因是人们低估了阳光在满足人类维生素 D-3 需求方面的作用。天然含有维生素 D 的食物很少，而那些含有维生素 D 的食物的维生素 D 含量差异很大。最近发现，野生捕获的鲑鱼的维生素 D-3 含量比养殖鲑鱼高出 75% 至 90%。生活在高纬度地区且容易缺乏维生素 D 会增加常见致命癌症、自身免疫性疾病、传染病和心血管疾病的风险，这应该提醒所有医疗保健专业人员维生素 D 对整体健康和福祉的重要性。
Throughout evolution, exposure to sunlight and the photosynthesis of vitamin D-3 in the skin has been critically important for the evolution of land vertebrates. During exposure to sunlight, the solar UVB photons with energies 290-315 nm are absorbed by 7-dehydrocholesterol in the skin and converted to previtamin D-3. Previtamin D-3 undergoes a rapid transformation within the plasma membrane to vitamin D-3. Excessive exposure to sunlight will not result in vitamin D intoxication because both previtamin D-3 and vitamin D-3 are photolyzed to several noncalcemic photoproducts. During the winter at latitudes above similar to 35 degrees, there is minimal, if any, previtamin D3 production in the skin. Altitude also has a significant effect on vitamin D-3 production. At 27 degrees N in November, very little (similar to 0.5%) previtamin D-3 synthesis was detected in Agra (169 in) and Katmandu (1400 in). There was an similar to 2- and 4-fold increase in previtamin D-3 production at similar to 3400 m and at Everest base camp (5300 in), respectively. Increased skin pigmentation, application of a sunscreen, aging, and clothing have a dramatic effect on previtamin D-3 production in the skin. It is estimated that exposure in a bathing suit to 1 minimal erythemal dose (MED) is equivalent to ingesting between 10,000 and 25,000 IU of vitamin D-2. The importance of sunlight for providing most humans with their vitamin D requirement is well documented by the seasonal variation in circulating levels of 25-hydroxyvitamin D [25(OH)D]. Vitamin D deficiency [i.e., 25(OH)D < 20 ng/ml] is common in both children and adults worldwide. Exposure to lamps that produce UVB radiation is an excellent source for producing vitamin D-3 in the skin and is especially efficacious in patients with fat malabsorption syndromes. The major cause of vitamin D deficiency globally is an underappreciation of sunlight's role in providing humans with their vitamin D-3 requirement. Very few foods naturally contain vitamin D, and those that do have a very variable vitamin D content. Recently it was observed that wild caught salmon had between 75% and 90% more vitamin D-3 compared with farmed salmon. The associations regarding increased risk of common deadly cancers, autoimmune diseases, infectious diseases, and cardiovascular disease with living at higher latitudes and being prone to vitamin D deficiency should alert all health care professionals about the importance of vitamin D for overall health and well being.