The Role of Sunlight in the Cutaneous Production of Vitamin D3

INTRODUCTION .. .... . . . . . ...... . . . .... . . . . . . ..... . . . . . . ........ . . . . . 375 HISTORICAL REVIEW........ . . . . . . .... . . . . . . . ....... . . .... . . . . . . . . ... . . . ......... . . . . . . 376 PHOTOCHEMISTRY OF PROVITAMIN D AND ITS PHOTOISOMERS ..... . ........ 377 FORMA nON OF VITAMIN D3 IN SKIN. . . .... . . . . . . . . . ..... . ....... . . . . . . . . . . . . .. 378 Photobiology of Vitamin D3 . .. .. . . . . . . ... .... . ........ . ...... . . . . . . . . . . . . 378 Action Spectra for the Formation of Previtamin D3 and Its Photoisomers . . .. . . . . . .. 380 Factors that Regulate the Cutaneous Production of Vitamin D3. . . . . ........ . . . . . . . . . . . 382 Photodegradation of Vitamin D3.... . . . . . . . . . . . . . . . . . . . . . . . . . . . . ....... . . . . . . . . . . ... 387 Artificial Light Sources and Vitamin D . . ....... . . . . . .. . . . . . . . . ..... . . . .. . . . . . . . . . .. . ....... . 387 EPIDEMIOLOGY OF VITAMIN D . . . . . ......... . . . . . . . . . . . . . . . . . ... . . ......... . . . . . . . 388 Vitamin D Deficiency in Children and Adults ...... . . . . . . . . . . . . . . . .. . .... . . . . . . . . . . . . . . . . . . 388 Environmental Factors . . . . . . . .... . . . . . . . .. . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 391 CONCLUSION . . . ....... . . . ........ . . ..... . . . . . . . . . . . . . .. . . . ...... . . . . . 393