Department of Dermatology, Medical Faculty, Technische Universitaet Dresden, Dresden, Germany.
Curr Probl Dermatol. 2021;55:296-315. doi: 10.1159/000517640. Epub 2021 Oct 25.
Vitamin D is generally accepted in its importance on the regulation of calcium homeostasis and bone metabolism. Moreover, further health effects due to vitamin D are under discussion. In its effect, vitamin D is more like a hormone. In the classic view, a vitamin is an essential nutrient, which cannot be synthesized independently in the body. Besides nutrition, vitamin D will be produced in the body itself. The skin contains the provitamin D3 7-dehydrocholesterol, a precursor of vitamin D. Provitamin D3 will be photoconverted to previtamin D3 by UVB radiation that penetrates the skin superficially. In this way, the vitamin D metabolism will be started independent of the nutrition. In everyday life, this photosynthesis will be carried out due to the solar UVB radiation penetrating the uncovered skin. In the same spectral waveband range of UVB radiation, which causes the beneficial health effect of starting the vitamin D metabolism, the UVB radiation causes simultaneously acute and chronic harmful health effects as UV erythema (sunburn), skin aging and skin cancer. There is no vitamin D production in the skin without simultaneous DNA damage in the skin. Against this background, risks and benefits have to be balanced carefully.
维生素 D 在调节钙稳态和骨骼代谢方面的重要性已被普遍认可。此外，维生素 D 对其他健康影响也在讨论之中。在其作用上，维生素 D 更像是一种激素。在经典观点中，维生素是一种必需的营养素，人体不能自行合成。除了营养，维生素 D 也会在体内产生。皮肤含有维生素 D 的前体物质 7-脱氢胆固醇。维生素 D3 前体物质会在穿透皮肤浅层的 UVB 辐射下光转化为维生素 D3 前体物质。这样，维生素 D 的新陈代谢就可以独立于营养而开始。在日常生活中，由于阳光中的 UVB 辐射穿透未被遮盖的皮肤，这种光合作用就会发生。在引起维生素 D 代谢启动这一有益健康效应的相同 UVB 辐射光谱波段范围内，UVB 辐射会同时对皮肤造成急性和慢性的有害健康影响，如晒伤、皮肤老化和皮肤癌。如果皮肤没有同时发生 DNA 损伤，皮肤就不会产生维生素 D。在这种背景下，必须谨慎权衡风险和收益。
