Spectral Character of Sunlight Modulates Photosynthesis of Previtamin D ₃ and Its Photoisomers in Human Skin

TLDR

The study measured previtamin D₃ synthesis from 7‑dehydrocholesterol in human skin under narrow‑band and simulated solar irradiation. Optimal previtamin D₃ production occurs at 295–300 nm, yielding up to 65 % conversion of 7‑dehydrocholesterol, whereas simulated solar light produces only ~20 % and alters the formation of lumisterol 3 and tachysterol 3, demonstrating that natural sunlight’s spectral composition profoundly influences skin photochemistry.

Abstract

The photosynthesis of previtamin D3 from 7-dehydrocholesterol in human skin was determined after exposure to narrow-band radiation or simulated solar radiation. The optimum wavelengths for the production of previtamin D3 were determined to be between 295 and 300 nanometers. When human skin was exposed to 295-nanometer radiation, up to 65 percent of the original 7-dehydrocholesterol content was converted to previtamin D3. In comparison, when adjacent skin was exposed to simulated solar radiation, the maximum formation of previtamin D3 was about 20 percent. Major differences in the formation of lumisterol3, and tachysterol3 from previtamin D3 were also observed. It is concluded that the spectral character of natural sunlight has a profound effect on the photochemistry of 7-dehydrocholesterol in human skin.