Skin photosynthesis refers to the process by which human skin converts sunlight into vitamin D. This process is not the same as the photosynthesis that plants use to produce energy. While plants convert sunlight into glucose, humans convert sunlight into previtamin D3, which is then converted into vitamin D. This process involves exposing the skin to ultraviolet (UV) radiation, specifically UVB rays, which penetrate the epidermis and cause the photolysis of 7-dehydrocholesterol (provitamin D3) into previtamin D3. This previtamin D3 then undergoes a thermal isomerization process that takes approximately 3 days to complete, finally converting it into vitamin D.
However, it is important to note that skin photosynthesis is not the only way to obtain vitamin D. Vitamin D can also be obtained through dietary sources like fatty fish, eggs, and fortified foods.
