Reassessing vitamin D supplementation in preterm infants: a prospective study and review of the literature.

Abstract

Objectives Recommendations for vitamin D (VitD) intake and target serum levels of 25(OH)D in preterm infants are diverse. We hypothesized that preterm infants with low birth weight (BW) have low dietary intake of VitD and therefore should be supplemented with higher amounts of VitD. Methods Infants with BW<2kg were supplemented with 600 units of VitD a day during the first 2-6weeks of life, whereas infants with BW>2kg continued with the routine supplementation of 400 units of VitD daily. Serum levels of 25(OH)D, calcium, phosphorous, alkaline phosphatase (AP) and parathyroid hormone (PTH) were assessed 24h after birth and before discharge. The total daily intake of vitD was calculated in each infant. Results Sixty-two infants were enrolled, 49 with BW<2kg. After birth, only 24% had sufficient levels of 25(OH)D, whereas before discharge 45 of 54 infants (83%) available for analysis reached sufficient levels of 25(OH)D. All 54 infants demonstrated significant elevation in serum levels of calcium, phosphorous, AP and significant reduction in PTH levels. The total daily intake of VitD was lower than recommended (800-1000IU/d) in 16 of 45 infants with BW<2kg (36%) and in all nine infants with BW>2kg. Nevertheless, only 2 of 25 infants with insufficient intake of VitD demonstrated insufficient levels of serum 25(OH)D. No case of vitamin D excess was recorded. Conclusions Increased supplementation of VitD (600IU/d) for premature newborns with BW<2kg is effective in increasing both total daily intake of VitD and serum levels of 25(OH)D.