Modifiable Determinants of Serum 25-Hydroxyvitamin D Status in Early Childhood<subtitle>Opportunities for Prevention</subtitle><alt-title>Determinants of Early Childhood Vitamin D Status</alt-title>

Objectives To determine the effect of modifiable dietary intake variables (current vitamin D supplementation and daily cow's milk intake) on 25-hydroxyvitamin D level in early childhood and to evaluate the relationship between these modifiable dietary factors and other largely nonmodifiable determinants of vitamin D status including skin pigmentation and season. Design Cross-sectional study. Setting Primary care pediatric and family medicine practices participating in the TARGet Kids! practice-based research network in Toronto, Ontario, Canada. Participants From December 2008 to June 2011, healthy children 1 to 5 years of age were recruited during a routine physician's visit. Interventions Survey, anthropometric measurements, and laboratory data were collected. A multivariable linear regression model was developed to examine the independent effects of vitamin D supplementation and daily volume of cow's milk on 25-hydroxyvitamin D level. Main Outcome Measures 25-Hydroxyvitamin D level. Results Blood was obtained in 1898 children. Two modifiable dietary intake variables, vitamin D supplementation and cow's milk, increased 25-hydroxyvitamin D level by 3.4 ng/mL (95% CI, 2-4 ng/mL) and 1.6 ng/mL per 250-mL cup per day (95% CI, 1-2 ng/mL), respectively. Two nonmodifiable variables reflecting cutaneous vitamin D synthesis (skin pigmentation and season) were also strongly associated with 25-hydroxyvitamin D status but accounted for a much smaller proportion of the explained variation in 25-hydroxyvitamin D level. The effect of vitamin D supplementation and milk intake on 25-hydroxyvitamin D level appeared similar regardless of skin pigmentation or season. Conclusion Two modifiable dietary intake variables (vitamin D supplementation and cow's milk intake) are the most important determinants of 25-hydroxyvitamin D status in early childhood.