The prevalence and determinants of use of vitamin D supplements among children in Alberta, Canada: a cross- sectional study

Background: Limited cutaneous synthesis due to low sun exposure and inadequate dietary intake makes vitamin D supplementation a necessity for many Canadian children. Identification of the factors associated with supplement use is necessary for public health awareness campaigns, but they have not been identified previously. Therefore, the purpose of this study was to assess the prevalence and the determinants of the use of vitamin D supplements among children in the province of Alberta, Canada. Methods: In 2014, a representative sample of grade five students (10-11 y) in Alberta (n = 2686) was surveyed. Data on dietary intake and use of vitamin D supplements were obtained using a modified Harvard Youth/Adolescent Food Frequency questionnaire. Mixed effect multiple logistic regression was employed to identify the key correlates of supplement use. Results: Use of vitamin D supplements by children was 29.45 % although only 11.83 % took supplements daily. Children who resided in a metropolitan area (OR = 1.32; 95 % CI: 1.06-1.65), were more physically active (2nd tertile: OR = 1.39; 95 % CI: 1.09-1.78 and 3rd tertile: OR = 1.70; 95 % CI: 1.33-2.16), or whose parents completed college (OR = 1.35; 95 % CI: 1.05-1.74) were more likely to take vitamin D supplements. Prevalence of use was highest among those who had a high vitamin D diet and those with under/normal body weight status, although supplement use was not statistically associated with either dietary vitamin D intake or weight status. Conclusions: A considerable proportion of children did not take vitamin D supplements. Region of residence, physical activity level and parental education were determinants of supplement use, independent of child's gender, household income, weight status and dietary practices. We suggest prioritizing public health efforts to support strategies to make parents aware of the importance of providing the correct dose of vitamin D supplements for their children to meet dietary recommendations.