Which vitamin is primarily made by the body when exposed to sunlight?

The vitamin that is primarily made by the body when exposed to sunlight is vitamin D. When the skin is exposed to ultraviolet B (UVB) radiation from the sun, a chemical reaction occurs that converts a cholesterol derivative in the skin into vitamin D3 (cholecalciferol). This process is a unique aspect of vitamin D, as it can be synthesized in sufficient quantities through sunlight exposure, making it different from most other vitamins that must be ingested through food or supplements.

Vitamin D plays a crucial role in calcium absorption, bone health, immune function, and numerous metabolic processes. Inadequate sunlight exposure can lead to deficiencies, particularly in regions with limited sunlight, highlighting the importance of this vitamin for maintaining overall health. Although other vitamins like A, B12, and C are vital for numerous bodily functions, they are not synthesized by the body in response to sunlight.