Obesity, lifestyle and socio-economic determinants of vitamin D intake: a population-based study of Canadian children.

OBJECTIVE: Vitamin D intake in childhood is primarily for the prevention of rickets. Inconsistent evidence has associated adequate blood concentrations with a decreased risk of certain health conditions. Further, obese individuals may have lower vitamin D status. The estimated average requirement (EAR) for children recently doubled to 400 IU/day. Our aim was to examine dietary intake of vitamin D in different body mass index (BMI) categories, in addition to assessing determinants.

METHODS: Data from two provincial surveys of grade 5 children, including a food frequency questionnaire and measured BMI, were used. Rao-Scott chi-square statistic tested the bivariate association between provinces and adequate dietary vitamin D intake. Key correlates were examined using multi-level logistic regression.

RESULTS: Those below the EAR differed between Alberta (78%) and Nova Scotia (81%). Those drinking <2 glasses of milk/day had 0.02 times the odds of meeting the EAR (95% CI: 0.01-0.02) compared to those drinking more. No significant difference was observed for BMI, though those consuming <1 glass of milk/day were more likely to be obese than those consuming ≥2 glasses/day. Income and physical activity were negatively correlated with meeting the EAR.

CONCLUSION: Many children did not meet the EAR for vitamin D from dietary sources and milk consumption was an important determinant. Given trends towards a more sedentary lifestyle and limited sun exposure, we recommend prioritizing public health efforts to support dietary vitamin D intake alongside interventions to increase physical activity and reduce sedentary behaviour. Further investigation is required to determine the need for targeted strategies for obese children.