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

Summary

We assessed vitamin D status and its correlates in the population-based Canadian Multicentre Osteoporosis Study (CaMos). Results showed that serum 25-hydroxyvitamin D levels <75?nmol/L were common. Given Canada??s high latitude, attention should be given to strategies for enhancing vitamin D status in the population.

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?C50?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.