Background: Inadequate sun exposure and dietary vitamin D intake can result in vitamin D insufficiency. However, limited data are available on actual vitamin D status and predictors in healthy individuals in different regions and by season. Methods: We compared vitamin D status [25-hydroxyvitamin D; 25(OH)D] in people < 60 years of age using data from cross-sectional studies of three regions across Australia: southeast Queensland (27°S; 167 females and 211 males), Geelong region (38°S; 561 females), and Tasmania (43°S; 432 females and 298 males). Results: The prevalence of vitamin D insufficiency (≤ 50 nmol/L) in women in winter/spring was 40.5% in southeast Queensland, 37.4% in the Geelong region, and 67.3% in Tasmania. Season, simulated maximum daily duration of vitamin D synthesis, and vitamin D effective daily dose each explained around 14% of the variation in 25(OH)D. Although latitude explained only 3.9% of the variation, a decrease in average 25(OH)D of 1.0 (95% confidence interval, 0.7-1.3) nmol/L for every degree increase in latitude may be clinically relevant. In some months, we found a high insufficiency or even deficiency when sun exposure protection would be recommended on the basis of the simulated ultraviolet index. Conclusion: Vitamin D insufficiency is common over a wide latitude range in Australia. Season appears to be more important than latitude, but both accounted for less than one-fifth of the variation in serum 25(OH)D levels, highlighting the importance of behavioral factors. Current sun exposure guidelines do not seem to fully-prevent vitamin D insufficiency, and consideration should be given to their modification or to pursuing other means to achieve vitamin D adequacy.

Item Type:	Refereed Article
Research Division:	Health Sciences
Research Group:	Epidemiology
Research Field:	Epidemiology not elsewhere classified
Objective Division:	Health
Objective Group:	Clinical health
Objective Field:	Clinical health not elsewhere classified
UTAS Author:	Van der Mei, IAF (Professor Ingrid van der Mei)
UTAS Author:	Ponsonby, AL (Professor Anne Ponsonby)
UTAS Author:	Blizzard, CL (Professor Leigh Blizzard)
UTAS Author:	Dwyer, T (Professor Terry Dwyer)
UTAS Author:	Jones, G (Professor Graeme Jones)
ID Code:	47508
Year Published:	2007
Web of Science® Times Cited:	178
Deposited By:	Menzies Institute for Medical Research
Deposited On:	2007-08-01
Last Modified:	2009-09-10
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