Which vitamin is synthesized when the skin is exposed to sunlight?

The synthesis of vitamin D in the skin is a crucial process that occurs when the skin is exposed to ultraviolet (UV) rays from sunlight. Specifically, UVB radiation stimulates the conversion of 7-dehydrocholesterol, a substance found in the skin, into vitamin D3 (cholecalciferol). This vitamin D3 is then further converted in the liver and kidneys to its active form, calcitriol, which plays vital roles in calcium homeostasis and bone health.

Unlike some other vitamins, which may be obtained primarily through dietary sources, vitamin D's synthesis in the skin makes it unique in terms of how our bodies can obtain it naturally. Adequate sunlight exposure can significantly influence vitamin D levels, making it essential for maintaining overall health, particularly for the immune system and bone maintenance.

While options such as vitamin A, B12, and C are essential nutrients, they do not undergo synthesis in the skin through sunlight exposure, highlighting the distinct role of vitamin D in the integumentary system and human health.