Correction of neonatal vitamin D status using 1000 IU vitamin D/d increased lean body mass by 12 months of age compared with 400 IU/d: a randomized controlled trial

Background: Intrauterine exposure to maternal vitamin D status <50 nmol/L of serum 25-hydroxyvitamin D [25(OH)D] may adversely affect infant body composition. Whether postnatal interventions can reprogram for a leaner body phenotype is unknown. Objectives: The primary objective was to test whether 1000 IU/d of supplemental vitamin D (compared with 40- IU/d) improves lean mass in infants born with serum 25(OH)D <50 nmol/L. Methods: Healthy. term, breastfed infants (Montreal, Canada, March 2016-2019) were assessed for serum 25(OH)D (immunoassay) 24-36 h postpartum. Infants with serum 25(OH)D <50nmol/L at 24-36 h were eligible for the trial and randomly assigned at baseline (1 mo postpartum) to 400 (29 males, 20 females) or 1000 IU/d (29 males, 20 females) of vitamin D until 12 mo. Infants (23 males, 18 females) with 25(OH)D >= 50 nmol/L (sufficient) formed a nonrandomized reference group provided 400 IU/d. Anthropometry, body composition (DXA), and serum 25(OH)D concentrations were measured at 1, 3, 6, and 12 mo. Results: At baseline, mean SD serum 25(OH)D concentrations in infants allocated to the 400 and 1000 IU/d vitamin D groups were 45.8 +/- 14.1 and 47.6 +/- 13.4, respectively; for the reference group it was 69.2 +/- 16.4 nmol/L. Serum 25(OH)D concentration increased on average to >= 50 nmol/L in the trial groups at 3-12 mo. Lean mass varied differently between groups over time; at 12 mo it was higher in the 1000 IU/d vitamin D group than in the 400 IU/d group (mean +/- SD: 7013 +/- 904.6 compared with 6690.4 +/- 1121.7 g, P = 0.0428), but not the reference group (mean +/- SD: 6715.1 +/- 784.6 g, P = 0.19). Whole-body fat mass was not different between the groups over time. Conclusions: Vitamin D supplementation (400 or 1000 IU/d) during infancy readily corrects vitamin D status, whereas 1000 IU/d modestly increases lean mass by 12 mo. The long-term implications require further research.

Automated summary

Supplementing with vitamin D during infancy improves vitamin D levels, and a daily dose of 1000 IU increases lean mass slightly.