# Improving Vitamin D Status in Preterm Newborns: A Randomized Trial of 800 vs. 400 IU/Day

## TL;DR

This study found that giving 800 IU/day of vitamin D3 to preterm newborns significantly improved their vitamin D levels and reduced hypovitaminosis D compared to 400 IU/day.

## Contribution

The study introduces a higher vitamin D3 dosage (800 IU/day) as an effective and safe protocol for preterm newborns in improving vitamin D status.

## Key findings

- 800 IU/day of vitamin D3 significantly increased serum 25(OH)D levels compared to 400 IU/day.
- The 800 IU/day group had a much lower prevalence of hypovitaminosis D at six weeks.
- No toxicity or significant differences in bone parameters were observed with the higher dose.

## Abstract

Background and Aims: Preterm newborns are particularly susceptible to hypovitaminosis D, potentially impairing bone mineralization. In Thailand, data on its prevalence and standardized supplementation protocols remain limited. This study aimed to compare the efficacy of two vitamin D3 dosages (400 IU/day vs. 800 IU/day) in improving serum vitamin D concentrations and metabolic bone parameters in preterm newborns. Methods: A randomized controlled trial was conducted in preterm newborns born at ≤32 weeks’ gestation or with birth weight ≤1500 g. Preterm newborns were randomized to receive either 400 IU or 800 IU/day of vitamin D3. Serum 25-hydroxyvitamin D (25(OH)D) was measured using electrochemiluminescence immunoassay (ECLIA). Metabolic bone parameters—including calcium, phosphorus, alkaline phosphatase, and albumin—were assessed at baseline and again at six weeks of age. Results: Of the 38 enrolled infants, baseline 25(OH)D levels were comparable between groups (14.8 ± 4.8 ng/mL in the 800 IU/day group vs. 14.7 ± 6.9 ng/mL in the 400 IU/day group). At six weeks, the 800 IU group demonstrated significantly higher 25(OH)D levels (47.3 ± 21.0 ng/mL vs. 32.0 ± 14.2 ng/mL; p = 0.013), with a large effect size (Cohen’s d = 0.85) and the difference-in-differences of +15.7 ng/mL. The prevalence of hypovitaminosis D declined from 89% to 5% in the 800 IU/day group and from 74% to 32% in the 400 IU/day group (p = 0.036). No significant differences in metabolic bone parameters or signs of toxicity were observed. Conclusions: Vitamin D3 supplementation at 800 IU/day significantly improved vitamin D status and reduced hypovitaminosis D in preterm newborns, without observed toxicity.