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

When the skin is exposed to sunlight, specifically ultraviolet B (UVB) rays, it synthesizes vitamin D. This process begins when UVB radiation converts 7-dehydrocholesterol, a compound in the skin, into previtamin D3, which is then converted into vitamin D3 (cholecalciferol) through heat from the body. After its initial formation in the skin, vitamin D undergoes further conversion in the liver and kidneys to form its active hormone, calcitriol, which plays a crucial role in calcium metabolism, bone health, and immune function.

Other vitamins, such as A, C, and E, are not synthesized in significant amounts through sunlight exposure. Vitamin A is primarily obtained from dietary sources, while vitamins C and E are also obtained through food and are known for their antioxidant properties but do not rely on sunlight for synthesis. This highlights the unique role of sunlight in the production of vitamin D, distinguishing it from other important vitamins in the body.