Trial of daily vitamin D supplementation in preterm infants.

OBJECTIVE To compare the effect of 800 vs 400 IU of daily oral vitamin D3 on the prevalence of vitamin D deficiency (VDD) at 40 weeks' postmenstrual age (PMA) in preterm infants of 28 to 34 weeks' gestation. METHODS In this randomized double-blind trial, we allocated eligible infants to receive either 800 or 400 IU of vitamin D3 per day (n = 48 in both groups). Primary outcome was VDD (serum 25-hydroxyvitamin D levels <20 ng/mL) at 40 weeks' PMA. Secondary outcomes were VDD, bone mineral content, and bone mineral density at 3 months' corrected age (CA). RESULTS Prevalence of VDD in the 800-IU group was significantly lower than in the 400-IU group at 40 weeks (38.1% vs. 66.7%; relative risk: 0.57; 95% confidence interval: 0.37-0.88) and at 3 months' CA (12.5% vs. 35%; relative risk: 0.36; 95% confidence interval: 0.14-0.90). One infant (2.4%) in the 800-IU group had vitamin D excess (100-150 ng/mL). Bone mineral content (mean ± SD: 79.6 ± 16.8 vs. 84.7 ± 20.7 g; P = .27) and bone mineral density (0.152 ± 0.019 vs. 0.158 ± 0.021 g/cm2; P = .26) were not different between the 2 groups. CONCLUSIONS Daily supplementation with 800 IU of vitamin D reduces the prevalence of VDD at 40 weeks' PMA and at 3 months' CA in preterm infants without showing any improvement in bone mineralization. However, there is a possibility that this dose may occasionally result in vitamin D excess.