Which vitamin is synthesized when skin is exposed to sunlight?

The correct choice is Vitamin D, which is a unique vitamin that the body can synthesize when the skin is exposed to ultraviolet (UV) rays from sunlight. Specifically, when UVB rays hit the skin, they convert a compound called 7-dehydrocholesterol into previtamin D3, which then undergoes further transformations in the body to become active Vitamin D.

Vitamin D plays a crucial role in calcium absorption and bone health, among other functions, making it vital for overall health. This synthesis mechanism makes Vitamin D distinct from other vitamins that primarily must be obtained from dietary sources.

In contrast, Vitamin A, B12, and C are not synthesized by the skin upon sun exposure; they must be sourced from food. Vitamin A is primarily obtained from animal products and some plant sources. Vitamin B12 is found mainly in animal products and is crucial for neurological function and blood cell formation. Vitamin C, an antioxidant, is abundant in fruits and vegetables, and is essential for the growth and repair of tissues in the body.