Location and Vitamin D synthesis: is the hypothesis validated by geophysical data?

Kimlin, Michael G., Olds, William J., & Moore, Michael R. (2007) Location and Vitamin D synthesis: is the hypothesis validated by geophysical data? Journal of Photochemistry and Photobiology B: Biology, 86(3), pp. 234-239.

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The literature reports strong correlations between UV exposure and latitude gradients of diseases. Evidence is emerging about the protective effects of UV exposure for cancer (breast, colo-rectal, prostate), autoimmune diseases (multiple sclerosis, type II diabetes) and even mental disorders, such as schizophrenia. For the first time, the available levels of vitamin D producing UV or "vitamin D UV" (determined from the previtamin D action spectrum) and erythemal (sunburning) UV from throughout the USA are measured and compared, using measurements from seven locations in the USA are measured and compared, using measurements from seven locations in the US EPA's high accuracy Brewer Spectrophotometer network. The data contest longstanding beliefs on the location-dependence and latitude gradients of vitamin D UV. During eight months of the year centered around summer (March-October), for all sites (from 18 degrees N to 44 degrees N latitude) the level of vitamin D UV relative to erythemal UV was equal (within the 95% confidence interval of the mean level). Therefore, there was no measured latitude gradient of vitamin D UV during the majority of the year across the USA. During the four cooler months (November-February), latitude strongly determines vitamin D UV. As latitude increases, the amount of vitamin D UV decreases dramatically, which may inhibit vitamin D synthesis in humans. Therefore, a larger dose of UV relative to erythemal UV is required to produce the same amount of vitamin D in a high latitude location. However, the data shows that at lower latitude locations (<25 degrees N), wintertime vitamin D UV levels are equal to summertime levels, and the message of increasing UV exposure during winter is irrelevant and may lead to excessive exposure. All results were confirmed by computer modeling, which was also used to generalize the conclusions for latitudes from 0 degrees to 70 degrees N. The results of this paper will impact on research into latitudinal gradients of diseases. In particular, it may no longer be correct to assume vitamin D levels in populations follow significant latitude gradients for a large proportion of the year.

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ID Code: 7734
Item Type: Journal Article
Refereed: Yes
Additional Information: For more information, please refer to the publisher's website (link above) or contact the author: m.kimlin@qut.edu.au
DOI: 10.1016/j.jphotobiol.2006.10.004
ISSN: 1011-1344
Divisions: Past > Research Centres > Centre for Health Research
Current > QUT Faculties and Divisions > Faculty of Health
Current > Institutes > Institute of Health and Biomedical Innovation
Copyright Owner: Copyright 2007 Elsevier.
Deposited On: 19 Jun 2007 00:00
Last Modified: 29 Feb 2012 13:38

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