Can vitamin D be made with exposure of the skin to sunlight from a window?
The answer is that it depends on whether the glass of the window is open or closed. Exposure of the skin to sunlight that has passed through plexiglas (Dupont Chemical Company, Memphis, TN, USA), most other plastics, or window pane glass (e.g., in buildings, motorized vehicles, covered strollers or prams, etc.) does not allow the endogenous production of vitamin D because these materials efficiently absorb ultraviolet B radiation (Holick 1994). Without UVB radiation, the skin cannot initiate the body’s process of making vitamin D. Holick, M. F. McCollum Award Lecture: Vitamin D: New horizons for the 21st century. Am J Clin Nutr 60: 619-30, 1994. 8. Are there any risks of vitamin D supplementation? Let me be clear that 1) prophylactic vitamin D supplementation is demonstrably useful for infants who are at risk of vitamin D deficiency and 2) no known risks of supplementation exist with 200 to 400 IU per day. Still, I believe that there is a great potential for harm from a recommendation
