Vitamin D status and recommendations to improve vitamin D status in Canadian youth
Little is known regarding the vitamin D status of Canadian youth. Our objectives were (i) to describe the vitamin D status of Quebec youth using a representative sample; (ii) to examine the relative contributions of diet, physical activity, and fat mass to the variance in plasma 25-hydroxyvitamin D(25(OH)D), the best biomarker of vitamin D status; and (iii) to examine the influence of household income and food insecurity on the intakes of dietary vitamin D, calcium, and dairy foods. To describe vitamin D status, we used data from the Quebec Child and Adolescent Health and Social Survey (QCAHS), which is a cross-sectional survey representative of Quebec youth aged 9, 13, and 16 years. For the second objective, 159 youth, aged 8 to 11 years, whose parents (at least one) were obese or had the metabolic syndrome, were used for cross-sectional analysis in the Quebec Adipose and Lifestyle InvesTigation in Youth (QUALITY). Fat mass was measured using dual X-ray absorptiometry (DXA), and physical activity was assessed by an accelerometer. Finally, we analyzed data from the Canadian Community Health Survey (CCHS), which collected data from 9 to 18 year olds (N = 8960), and was representative of Canadian youth. From this survey a single 24-h dietary recall, measured height and weight, sociodemographic, and food insecurity information were available. In both the QUALITY and QCAHS study, >90% of youth had suboptimal vitamin D levels (plasma 25(OH)D < 75 nmol·L–1) at the end of winter and beginning of spring. In the QCAHS study, older youth had a higher prevalence of vitamin D deficiency (25(OH)D < 27.5 nmol·L–1) (>10%) than younger youth, and girls from low-income households had lower plasma 25(OH)D concentrations. In the QUALITY study, milk consumption and physical activity had modest associations with plasma 25(OH)D, corresponding to 2.9 nmol·L–1 and 2.1 nmol·L–1 higher plasma 25(OH)D per standard deviation increase in these exposures, respectively. In the CCHS study, we found evidence that milk intake was being displaced by sweetened beverages among low-income boys and food insecure girls. We conclude that population-wide measures to increase dietary vitamin D intake should be examined in Canadian youth.