Photochem. Photobiol. Sci., 2013, June, DOI: 10.1039/C3PP50041A
Richard McKenzie, richard.mckenzie at niwa.co.nz a Ben Liley,a Paul Johnston,a Robert Scragg,b Alistair Stewart,b Anthony I. Reederc and Martin W. Allend
A National Institute of Water and Atmospheric Research, NIWA Lauder, Central Otago, New Zealand
B School of Population Health, University of Auckland, Auckland, New Zealand
C Cancer Society Social and Behavioural Research Unit, Department of Preventive and Social Medicine, Dunedin School of Medicine, New Zealand
D MacDiarmid Institute for Advanced Materials and Nanotechnology, University of Canterbury, Christchurch, New Zealand
To clarify the relation between UV exposure and vitamin D status, 201 volunteers wore personal electronic UV dosimeters during daylight hours, to record their UV exposure over a 10 week period when ambient UV levels were significantly less than the summer maxima. Blood samples to determine serum 25-hydroxyvitamin D3 [25(OH)D3] levels were taken at the end of week 4 and week 8.
Participants were then given a single full-body exposure of approximately 2 SED from one of four artificial UV sources with different spectral outputs and a further blood sample taken at study completion, nominally week 10. The artificial UV exposure reversed the mean seasonal decline in 25(OH)D3. Increases in 25(OH)D3 from week 8 to week 10 were related to total UV exposure, including the ambient sun exposures. These exposures were weighted by the erythemal action spectrum and separately for three different action spectra for pre-vitamin D production. For the erythema weighting function, 25(OH)D3 increased 1.78 ± 0.25 nmol per litre per SED, a value consistent with other studies.
Any differences due to age, BMI, gender, and skin reflectance were not statistically significant.
Ethnicity differences were the only significant factor, with Asians producing the least vitamin D, and Maori the most. There was no statistically significant improvement in consistency between sources for any of the three pre-vitamin weightings compared with that for erythema. Further work is needed to verify which vitamin D action spectrum is most appropriate. Nevertheless, these small doses of UV from artificial sources were helpful in quantifying the relationship between UV exposure and vitamin D status among the New Zealand population.
- SED is defined for UVA (tanning) not UVB (Vitamin D), so how could they use it if there was no UVA?
- No mention of amount of UVA in the light sources.
UVA may decrease the amount of vitamin D generated
- SED is strongly a function of skin color (see graph below).
Wonder if this study took that into consideration?
- SED definition (from 1997)
- No indication of age-range of participants. Were they, for example, in the range 20-40 years?
- No indication of BMI range of participants. Were none of them obese?
- Complex relationship between UVB and vitamin D – April 2012
- No – 10 minutes per day of sun-UVB is NOT enough
- All items in Noontime Sun
- Dark skin does not generate as much vitamin D from the same amount of UV – Nov 2011
- Even small amounts of UVB result in increased vitamin D levels – March 2012 many items by McKenzie (an author of this study)