Vitamin D status and recommendations to improve vitamin D status in Canadian youth

Abstract

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.