Am J Clin Nutr. 1995 Mar;61(3 Suppl):638S-645S.
All vertebrates, including humans, obtain most of their daily vitamin D requirement from casual exposure to sunlight. During exposure to sunlight, the solar ultraviolet B photons (290-315 nm) penetrate into the skin where they cause the photolysis of 7-dehydrocholesterol to precholecalciferol. Once formed, precholecalciferol undergoes a thermally induced rearrangement of its double bonds to form cholecalciferol. An increase in skin pigmentation, aging, and the topical application of a sunscreen diminishes the cutaneous production of cholecalciferol. Latitude, season, and time of day as well as ozone pollution in the atmosphere influence the number of solar ultraviolet B photons that reach the earth's surface, and thereby, alter the cutaneous production of cholecalciferol.
In Boston, exposure to sunlight during the months of November through February will not produce any significant amounts of cholecalciferol in the skin.
Because windowpane glass absorbs ultraviolet B radiation, exposure of sunlight through glass windows will not result in any production of cholecalciferol. It is now recognized that vitamin D insufficiency and vitamin D deficiency are common in elderly people, especially in those who are infirm and not exposed to sunlight or who live at latitudes that do not provide them with sunlight-mediated cholecalciferol during the winter months. Vitamin D insufficiency and deficiency exacerbate osteoporosis, cause osteomalacia, and increase the risk of skeletal fractures. Vitamin D insufficiency and deficiency can be prevented by encouraging responsible exposure to sunlight and/or consumption of a multivitamin tablet that contains 10 micrograms (400 IU) vitamin D.
PDF is attached at the bottom of this page
- Search for Holick in the title 35 items as of Jan 2014
- Overview UV and vitamin D
- UV Radiation and the Skin June 2013
- UV, sunshine, and vitamin D (87 charts) - Holick March 2013
- UVA decreased vitamin D levels (again) – July 2013
- All items in category UV and vitamin D
338 itemsEnvironmental factors that influence the cutaneous production of vitamin D – Holick 1995 5476 visitors, last modified 06 Jan, 2014,This page is in the following categories (# of items in each category)