Comments by "N Marbletoe" (@nmarbletoe8210) on "Vitamin D Update" video.

  1. Good observation! There is a small amount of UV that does pass through a window. Otherwise, as you say, books would not bleach. I could say "but obviously it's not much" but why not me look it up? OK... data collection: 1. What wavelength? "Vitamin D is made when UV (more precisely, UVB rays) react with a compound (7-dehydrocholesterol) in the skin. The best rays for UV synthesis have wavelengths between 270–300 nm. https://www.sciencelearn.org.nz/resources/1313-vitamin-d-and-uv 2. Absorption? The results showed that the building window-glasses were opaque to UVB but transparent to UVA while the non-window-glasses exhibited transparency in the UVB and UVA spectral regions. The car-glass (laminated), used as windscreen, was opaque to UVB and UVA while the side-glass (non-laminated) was opaque to UVB but transparent to UVA." https://www.researchgate.net/publication/282419276_Spectroscopic_Study_of_UV_Transparency_of_Some_Materials This leads to a new hypothesis, that UVA is bleaching the books, not UVB. 3. Does UVA fade things? "Fading of interior furnishings is often attributed to ultraviolet radiation (UV) from the sun passing through windows onto interior surfaces. However, UV is not the only portion of the solar spectrum which can damage artwork or furnishings inside buildings. Virtually the whole spectrum is of concern..." http://www.fsec.ucf.edu/en/consumer/buildings/basics/windows/fading.htm I think that supports the hypothesis that UVA is fading our indoor objects, but this doesn't help get Vitamin D because D is made with UVB, which is filtered out nearly completely.
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  2. sun?
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  3. Don't need to expose your face. Arms and legs should be good, or even just arms... the skin produces an amazing amount of D when in sunlight! One webite said we could make 1000 IU in ~ four minutes (but i don't know how much skin was in that calculation).
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