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75 percent of Canadians less than 30 ng vitamin D in winter – Aug 2010

25-Hydroxyvitamin D in Canadian adults: biological, environmental, and behavioral correlates.

Osteoporos Int. 2010 Aug 21.
Greene-Finestone LS, Berger C, de Groh M, Hanley DA, Hidiroglou N, Sarafin K, Poliquin S, Krieger J, Richards JB, Goltzman D; CaMos Research Group.
Public Health Agency of Canada, Ottawa, Ontario, Canada, linda.greene-finestone at phac-aspc.gc.ca.

INTRODUCTION: Inadequate vitamin D has been implicated as a risk factor for several clinical disorders. We assessed, in a Canadian cohort, vitamin D status and its correlates, based on serum 25-hydroxyvitamin D 25(OH)D, the best functional indicator of vitamin D status.

METHODS: We studied 577 men and 1,335 women 35+ years from seven cities across Canada in the randomly selected, population-based Canadian Multicentre Osteoporosis Study (CaMos). Participants completed a comprehensive questionnaire. Serum 25(OH)D was measured by immunoassay. Multivariate linear regression modeling assessed the association between 25(OH)D and determinants of vitamin D status.

RESULTS: Participants (2.3%) were deficient in 25(OH)D (<27.5 nmol/L); a further 18.1% exhibited 25(OH)D insufficiency (27.5-50 nmol/L). Levels <75 nmol/L were evident in 57.5% of men and 60.7% of women and rose to 73.5% in spring (men) and 77.5% in winter (women); 25(OH)D <50 nmol/L was </=10% year round for those supplementing with >/=400 IU vitamin D/day but was 43.9% among those not supplementing in winter and spring. The strongest predictors of reduced 25(OH)D for both men and women were winter and spring season, BMI >/=30, non-white ethnicity, and lower vitamin D supplementation and its modification by fall and winter.

CONCLUSIONS: In this national Canadian cohort, vitamin D levels <75 nmol/L were common, particularly among non-white and obese individuals, and in winter and spring. Vitamin D intake through diet and supplementation and maintenance of normal weight are key modifiable factors for enhancing vitamin D status and thus potentially influencing susceptibility to common chronic diseases. PMID: 20730415
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See also VitaminDWiki