Vitamin D status: multifactorial contribution of environment, genes and other factors in healthy Australian adults across a latitude gradient
The Journal of Steroid Biochemistry and Molecular Biology Available online 8 February 2013
Robyn M. Lucasa, robyn.lucas at anu.edu.au
Anne-Louise Ponsonby b, Keith Dear a, Patricia C. Valery c, Bruce Taylor d, Ingrid van der Mei d, Anthony J. McMichael a, Michael P. Pender e,
Caron Chapman f, Alan Coulthard e, Trevor J. Kilpatrick g, Jim Stankovich d, David Williams h, Terence Dwyer b
a National Centre for Epidemiology and Population Health, The Australian National University, Canberra, Australia 0200
b Murdoch Childrens Research Institute, Melbourne, Australia 3052
c Menzies School of Health Research, Brisbane, Australia 4000
d Menzies Research Institute, Hobart, Australia 7001
e The University of Queensland and Royal Brisbane and Women's Hospital, Brisbane, Australia 4006
f Barwon Health, Geelong, Australia 3220
g Centre for Neuroscience, The University of Melbourne, Melbourne, Australia 3010
h John Hunter Hospital, Newcastle, Australia 2310
Vitamin D deficiency is common and implicated in risk of several human diseases. Evidence on the relative quantitative contribution of environmental, genetic and phenotypic factors to vitamin D status (assessed by the serum concentration of 25-hydroxyvitamin D, 25(OH)D) in free-living populations is sparse.
We conducted a cross-sectional study of 494 Caucasian adults aged 18–61 years, randomly selected from the Australian Electoral Roll according to groups defined by age, sex and region (spanning 27°-43°South). Data collected included personal characteristics, sun exposure behaviour, biomarkers of skin type and past sun exposure, serum 25(OH)D concentration and candidate single nucleotide polymorphisms.
Ambient ultraviolet radiation (UVR) levels in the month six weeks before blood sampling best predicted vitamin D status.
Serum 25(OH)D concentration increased by 10nmol/L as reported time in the sun doubled.
Overall, 54% of the variation in serum 25(OH)D concentration could be accounted for:
- 36% of the variation was explained by sun exposure-related factors;
- 14% by genetic factors (including epistasis) and
- 3.5% by direct measures of skin phenotype.
Novel findings from this study are demonstration of gene epistasis, and quantification of the relative contribution of a wide range of environmental, constitutional and genetic factors to vitamin D status. Ambient UVR levels and time in the sun were of prime importance but it is nonetheless important to include the contribution of genetic factors when considering sun exposure effects.
- Ambient ultraviolet radiation six weeks prior to blood sampling best predicted vitamin D status.
- Time in the sun predicts serum 25-hydroxyvitamin D concentration in a logarithmic association.
- Environmental, phenotypic and genetic factors explained over 50% of the variation in vitamin D.
- The most important environmental predictor was ambient ultraviolet radiation.
- Gene epistasis in vitamin D pathway geneshas a significant influence on vitamin D status.
Fig. 2. Predicted mean 25(OH)D levels (nmol/L) in relation to hours in the sun in the season that was 6 weeks prior to blood collection.
Predicted values were derived from a model accounting for the non-genetic factors shown in Table 2.
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