Introduction
Vitamin D status at birth reflects maternal-fetal transfer of 25-hydroxyvitamin D (25[OH]D).A dose-response relation exists between vitamin D intake and 25(OH)D concentration in infants, and the lower the initial concentration, the greater the rise in vitamin D status.The objective of this study was to compare the effect of 1000 IU per day of oral vitamin D supplementation vs 400 IU per day on bone health from age 1 to 12 months in infants born with serum 25(OH)D concentrations less than 50 nmol/L and whose mothers had an intent to breastfeed for at least 3 months. Our hypothesis was that infants born with serum 25(OH)D concentrations less than 50 nmol/L and provided with a supplement of 400 IU per day (compared with 1000 IU per day) would have lower bone mineral accretion by 3 months without resolution at age 12 months.