An acknowledged benefit of exposure to ultraviolet radiation is synthesis of vitamin D in human skin. Here we have defined a standard vitamin D dose based upon recommended requirements for vitamin D, and present a simplified web-based tool that enables the user to calculate associated exposure times for any time and place The simplified www page is convenient for users unfamiliar to radiative transfer modelling, because the model input is limited and more intuitive.
The sky conditions in the simple www page are somewhat different than the complex web page. "Cloudless" is a very clear, pristine atmosphere with an aerosol turbidity coefficient (Ångström β) of 0.02. "Scattered clouds" in the simple version correspond indeed to scattered clouds in the complex version, but with a cloud fraction of 30%. "Broken clouds" in the simple version are not "broken clouds with radiation enhancement" as in the complex version, but are scattered clouds like the previous with a cloud fraction of 70%. "Overcast" in simple version is the same as in the complex version. For all cloudy scenarios simple version, the cloud liquid water column is set to 240 g m-2.
Ozone layer thicknesses of "Thin", "Medium" and "Thick" refer to ozone columns of 200, 350 and 500 DU, respectively. DU = Dobson unit (1 DU = 1matm-cm, equivalent to the thickness of 0.01 mm of pure ozone at standard conditions of temperature [273.15K] and pressure [1013.25 Pa]).
All other values should be self-explanatory, and agree with the more complex www page.
Author: Ola Engelsen
Norwegian Institute for Air Research
Copyright © 2006 Ola Engelsen
Last modified 20th September 2006.
The current model has undergone internal checking and validation. If you have any questions or comments on this service and how it could be improved for your needs, please contact the author.
If you use this program and publish the results, I would appreciate a lot if you cite it:
Webb, A.R. and O. Engelsen (2006) Calculated Ultraviolet Exposure Levels for a H ealthy Vitamin D Status. Photochemistry and Photobiology. 82(6), 1697-1703.
A reprint is freely available on the internet from this link
The underlying simulations are done using the following model:
Engelsen O. and Kylling A., Fast simulation tool for ultraviolet radiation at the Earth's surface. Optical Engineering, 44 (4), 041012 (2005).
The recommended blood serum level is under debate [Dawson-Hughes et al., 2005], but 30 ng/mL is widely recommended e.g., by [Hollis, 2005]. Clinical studies found 500-1,000 IU of vitamin D/day maintains blood serum levels of 30 ng/mL (75 nmol/L) [Tangpricha et al, 2003], [Heaney et al., 2003], [Meier et al., 2004].
In order to assess the fraction of the body that is exposed to the sun, the Lund and Browder Chart for skin burns provides an indication: Face 3.5%, neck 2%, trunk 26%, hands 6%, arms 14%, legs 14%, thighs 18%.
Heaney R. P., K. M. Davies, T. C. Chen, et al. (2003) Human serum 25-hydroxycholecalciferol response to extended oral dosing with cholecalciferol. Am. J. Clin. Nutr. 77:204-210. Erratum in: Am. J. Clin. Nutr 2003;78:1047.
Holick, M. F. (2004a) The Vitamin D Advantage, iBooks.
Holick M. F. (2004c) Vitamin D: importance in the prevention of cancers, type 1 diabetes, heart disease and osteoporosis. Am.J.Clin.Nutr. 79: 362-7
Hollis B. W. (2005) Circulating 25-hydroxyvitamin D levels indicative of vitamin D sufficiency: implications for establishing a new effective dietary intake recommendation for vitamin D. J. Nutr. 135:317-322.
MacKinley, A. F. and B. L. Diffey, (Eds.) (1987) A reference action spectrum for ultraviolet induced erythema in human skin, CIE J., 6(1), 17-22.
MacLaughlin, J. A., R. R. Anderson and M. F. Holick (1982) Spectral character of sunlight modulates photosynthesis of previtamin D3 and its photoisomers in human skin. Science. 216, 1001-1003.
Tangpricha V., P. Koutkia, S. M. Rieke, et al. (2003) Fortification of orange juice with vitamin D: novel approach for enhancing vitamin D nutritional health. Am J Clin Nutr 77:1478-1483.
Webb, A. R. , L. Kline and M. F. Holick (1988) Influence of season and latitude on the cutaneous synthesis of vitamin D3: exposure to winter sunlight in Boston and Edmonton will not promote vitamin D3 synthesis in human skin. J. Clin. Endocrinol. Metab. 67, 373-378.