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Open Access Research article

Solar ultraviolet-B radiation and vitamin D: a cross-sectional population-based study using data from the 2007 to 2009 Canadian Health Measures Survey

Jamie A Greenfield123, Philip S Park4, Ellie Farahani45, Suneil Malik1, Reinhold Vieth6, Norman A McFarlane4, Theodore G Shepherd4 and Julia A Knight23*

Author Affiliations

1 Office of Biotechnology, Genomics and Population Health, Public Health Agency of Canada, 180 Queen Street West, Toronto, Canada

2 Dalla Lana School of Public Health, University of Toronto, 155 College Street, Toronto, Canada

3 Samuel Lunenfeld Research Institute, Mount Sinai Hospital, , 60 Murray street, Box 18, Toronto, Canada

4 Department of Physics, University of Toronto, 60 St. George Street, Toronto, Canada

5 Centre for EnvironmentUniversity of Toronto, 33 Willcocks Street, Toronto, Canada

6 Department of Pathology and Laboratory Medicine, Mount Sinai Hospital, 600 University Avenue, Toronto, Canada

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BMC Public Health 2012, 12:660  doi:10.1186/1471-2458-12-660

Published: 15 August 2012

Abstract

Background

Exposure to solar ultraviolet-B (UV-B) radiation is a major source of vitamin D3. Chemistry climate models project decreases in ground-level solar erythemal UV over the current century. It is unclear what impact this will have on vitamin D status at the population level. The purpose of this study was to measure the association between ground-level solar UV-B and serum concentrations of 25-hydroxyvitamin D (25(OH)D) using a secondary analysis of the 2007 to 2009 Canadian Health Measures Survey (CHMS).

Methods

Blood samples collected from individuals aged 12 to 79 years sampled across Canada were analyzed for 25(OH)D (n = 4,398). Solar UV-B irradiance was calculated for the 15 CHMS collection sites using the Tropospheric Ultraviolet and Visible Radiation Model. Multivariable linear regression was used to evaluate the association between 25(OH)D and solar UV-B adjusted for other predictors and to explore effect modification.

Results

Cumulative solar UV-B irradiance averaged over 91 days (91-day UV-B) prior to blood draw correlated significantly with 25(OH)D. Independent of other predictors, a 1 kJ/m2 increase in 91-day UV-B was associated with a significant 0.5 nmol/L (95% CI 0.3-0.8) increase in mean 25(OH)D (P = 0.0001). The relationship was stronger among younger individuals and those spending more time outdoors. Based on current projections of decreases in ground-level solar UV-B, we predict less than a 1 nmol/L decrease in mean 25(OH)D for the population.

Conclusions

In Canada, cumulative exposure to ambient solar UV-B has a small but significant association with 25(OH)D concentrations. Public health messages to improve vitamin D status should target safe sun exposure with sunscreen use, and also enhanced dietary and supplemental intake and maintenance of a healthy body weight.

Keywords:
25-Hydroxyvitamin D; Solar ultraviolet-B irradiance; Public health