Vitamin D Research Today is a free monthly online journal that collates and summarizes the latest research about Vitamin D, including details on sources, melanin, benefits, deficiency, supplements, calcium absorption.

Who, what, where and when-influences on cutaneous vitamin D synthesis.

Webb AR

University of Manchester, UK. ann.webb@umist.ac.uk

The synthesis of vitamin D in skin is a two-stage process that begins with the production of previtamin D after irradiation of 7-dehydrocholesterol by ultraviolet (UV) radiation. A number of personal and environmental factors control the probability of a suitable UV photon reaching a molecule of 7-dehydrocholesterol in the skin. These are astronomical factors that govern the solar zenith angle (SZA), and the local state of the atmosphere, determining the available solar UV radiation; skin pigmentation and age, determining competing absorbers of UV radiation and available 7-dehydrocholesterol; individual behaviour in the local surroundings, determining exposure of unprotected skin to available UV radiation. The only one of these influences that can be determined unequivocally for any situation is the SZA. The other influences must be considered either as individual case studies, or be represented by "typical" and "idealised" situations for the weather, skin and behaviour. At large SZAs there is insufficient solar UV radiation to initiate significant vitamin D synthesis. At smaller SZAs assessment of solar exposure necessary for vitamin D synthesis can only be indicative and application of any such assessment necessarily requires awareness of both self- and the local environment.

Published 27 July 2006 in Prog Biophys Mol Biol, 92(1): 17-25.
Full-text of this article is available online (may require subscription).

© 2004-2008 Vitamin D Research Today. All Rights Reserved.