Question

Sunlight produces vitamin _____ in the human skin.

• A. A
• B. B
• C. D
• D. E

Answer 1

The correct option is C D

Vitamin D is not one chemical but many. The natural type is produced in the skin from a universally present form of cholesterol, 7-dehydrocholesterol. Sunlight is the key: Its ultraviolet B (UVB) energy converts the precursor to vitamin D${}_3$. In contrast, most dietary supplements are manufactured by exposing a plant sterol to ultraviolet energy, thus producing vitamin D${}_2$. Because their function is almost identical, D${}_2$ and D${}_3$ are lumped together under the name vitamin D, but neither will function until the body works its magic. The sun’s energy turns a chemical in your skin into vitamin D${}_3$, which is carried to your liver and then your kidneys to transform it to active vitamin D.