Determinants of 25-Hydroxyvitamin D Concentrations in Infants and Toddlers

Background: Resurgence of rickets and recognition of excessive prevalence of hypovitaminosis D among all age groups in the western hemisphere have refocused attention on vitamin D nutrition. Objective: To examine the prevalence of hypovitaminosis D [25-hydroxyvitamin D [25(OH)D] < 30ng/mL] and characterize the determinants of 25(OH)D concentrations in 8 to 24-month-old healthy infants and toddlers living in Pittsburgh, Pennsylvania. Methods: Serum 25(OH)D concentrations were measured and dietary intake of vitamin D, mode of feeding, summertime sun exposure characteristics, and skin color (sun-reactive skin type and melanin index) were assessed. Results: A total of 111 healthy 8 to 24-month-old children (mean age [+/-SD] 14.4 [+/-3.5] months; male, 51%; black, 67%) were studied. Serum 25(OH)D concentration was <30 ng/mL in 16% (n=18) of the children. Median (interquartile) 25(OH)D concentration was lower in children who were >= 13 months vs. <13 months of age [35 (31, 40.5) vs. 40 (35.8, 44.3) ng/mL, p=0.013]; with sun-reactive skin type IV and V vs. I, II, and III [36 (31, 41) vs. 44 (36.5, 48.5) ng/mL, p=0.001]; and examined during fall/winter vs. spring/summer [35.5 (32.5, 38.5) vs. 39 (32.5, 44) ng/mL, p=0.05]. Age and skin type were significant independent predictors of 25(OH)D. Conclusions: Concentrations of 25(OH)D tend to be lower in infants and toddlers during fall/winter, and in children who are older (>= 13 months vs. <13 months of age) and have darker skin tone. Benefits of enhancement of 25(OH)D concentrations during fall/winter and in children with higher sun-reactive skin type need further exploration.