Conclusions
In conclusion, in infants with 25(OH)D concentrations less than 50 nmol/L at birth, both 400 and 1000 IU per day of vitamin D supplementation normalized and maintained 25(OH)D concentrations that align with skeletal health. The 1000 IU per day dosage of vitamin D supplementation did not lead to measurable improvements in bone health outcomes. Evidence from this Montreal-based study suggests that the standard of care of 400 IU per day is enough to support bone health of breastfed infants born with serum 25(OH)D concentrations less than 50 nmol/L.