Cholecalciferol is produced by irradiation of 7-dehydrocholesterol with ultraviolet light either from the sun or from an artificial source.

胆钙化醇是7 ？脱氢胆固醇经日光或人工来源的紫外线照射而产生的。

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Cholecalciferol is produced by irradiation of 7-dehydrocholesterol with ultraviolet light either from the sun or from an artificial source.

胆钙化醇是7脱氢胆固醇经日光或人工来源的紫外线照射而产生的。

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First of all, the vitamin is not actually absorbed from the sunlight, but rather is made by the body when certain wavelengths of light activate a chemical called 7-dehydrocholesterol within the skin.

首先，其实人体并不能从日光中吸收维生素，而是特定波长的光(中波紫外线，UVB)可以激活皮肤内一种叫做7 -脱氢胆固醇的化学物。

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The action of ultra-violet light from the sun on a molecule called 7-dehydrocholesterol, found in the skin, turns it into the vitamin.

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