What is the formula for producing the active form of vitamin D?

The process of producing the active form of vitamin D starts with 7-dehydrocholesterol, a compound found in the skin. When exposed to ultraviolet (UV) radiation from sunlight, 7-dehydrocholesterol undergoes a conversion to cholecalciferol, which is also known as vitamin D3. This transformation is a key step in vitamin D synthesis, as cholecalciferol is then further processed in the liver and kidneys to produce the biologically active form, calcitriol (1,25-dihydroxyvitamin D).

Understanding this, the correct option highlights the initial step in the synthesis of vitamin D from its precursors present in the skin, demonstrating the importance of sunlight exposure for vitamin D production. This process is crucial for maintaining proper calcium and phosphorus balance in the body and plays a significant role in bone health and immune function.