Higher vitamin D intake in preterm infants fed an isocaloric, protein- and mineral-enriched postdischarge formula is associated with increased bone accretion.

During the first half of infancy, bone accretion in preterm infants fed an isocaloric, protein- and mineral-enriched postdischarge formula (PDF) is higher compared with those fed term formula (TF) or human milk (HM). This may be related to higher protein, calcium, phosphorus, and vitamin D intakes. This study investigated serum calcium, phosphate, and 25-hydroxyvitamin D [25(OH)D] in relation to bone mineral content (BMC) in PDF-, TF-, and HM-fed preterm infants between term age (40 wk postmenstrual age) and 6 mo corrected age (CA). Between term age and 6 mo CA, 52 preterm infants were fed PDF (per 100 mL: 67 kcal, 1.7 g protein, 65 mg calcium, 38 mg phosphorus, 56 IU vitamin D), 41 were fed TF (per 100 mL: 67 kcal, 1.47 g protein, 50 mg calcium, 30 mg phosphorus, 48 IU vitamin D), and 46 were fed HM. Serum calcium, phosphorus, and 25(OH)D were measured at term age and at 3 and 6 mo CA. BMC (g) was measured by whole-body dual-energy X-ray absorptiometry at term age and at 6 mo CA. Between term age and 6 mo CA, intakes of calcium, phosphorus, and vitamin D were significantly higher in PDF- compared with TF-fed infants, and PDF-fed infants reached significantly higher serum 25(OH)D concentrations at 6 mo CA (103 ± 24.3 vs. 92.8 ± 15.5 nmol/L, P = 0.003). Between term age and 6 mo CA, increases in serum 25(OH)D were associated with an increase in BMC (β = 0.001; 95% CI: 0.00, 0.003; P = 0.046). In conclusion, during the first 6 mo postterm, higher vitamin D intake and greater increase in serum 25(OH)D concentration in PDF-fed preterm infants were associated with increased bone accretion.