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

• A. Vitamin A
• B. Vitamin C
• C. Vitamin D
• D. Vitamin E

Answer: (C)

Vitamin D is primarily synthesized in the skin when it is exposed to sunlight, specifically ultraviolet B (UVB) radiation. When sunlight strikes the skin, it triggers a chemical reaction that converts a cholesterol derivative in the skin (7-dehydrocholesterol) to previtamin D3, which is then converted into active vitamin D (calcitriol) through further processes in the liver and kidneys. This vitamin is essential for various bodily functions, especially for maintaining calcium levels and supporting bone health.

Other vitamins listed in the options are not synthesized in the skin through sunlight exposure. Vitamin A is obtained from dietary sources and is important for vision, immune function, and skin health. Vitamin C is primarily a dietary vitamin known for its antioxidant properties and role in collagen synthesis. Vitamin E also comes from dietary sources and acts as an antioxidant, protecting the skin from damage. Thus, the unique ability of the skin to synthesize vitamin D in response to sunlight distinguishes it as the correct answer in this context.