Discussion
SECONDARY
In the absence of robust trials investigating the effect of a dose of vitamin D supplementation higher than the standard of care (400 IU per day) on bone mineral accretion and density in infants born with 25(OH)D concentrations less than 50 nmol/L, this prespecified secondary analysis of a randomized clinical trial provides information to help guide recommendations for vitamin D supplementation in this understudied population. Infants at elevated risk of insufficient vitamin D status provided with a daily supplement of 400 IU (compared with 1000 IU per day) did not have compromised bone outcomes (WB BMC, LS BMC, or LS BMD) across infancy. This is in line with findings from a study by Ziegler et al,The results of this study and othersIn accordance with no evidence of a dose-response in bone mass with vitamin D supplementation and achievement of sufficient vitamin D status, no differences in biomarkers of bone formation or resorption due to vitamin D dose were noted in our trial from age 1 to 12 months. These markers lack reference data in infancy, and efforts to standardize biomarkers of bone metabolism are needed.Serum 25(OH)DThe lack of dose-response of 1,25(OH)