What vitamin is produced when the skin is exposed to sunlight?

When the skin is exposed to sunlight, it synthesizes vitamin D through a process that involves the conversion of cholesterol in the skin to vitamin D3 (cholecalciferol). This process is initiated when ultraviolet (UV) rays from sunlight interact with the skin, making vitamin D a unique nutrient because it can be produced by the body naturally rather than only being obtained through diet. Vitamin D plays a crucial role in maintaining bone health, regulating calcium and phosphate in the body, and supporting the immune system. This is why the answer is vitamin D, as it is specifically the vitamin that is generated in response to sunlight exposure.