Vitamin D nutritional status of premature infants supplemented with 500 IU vitamin D2 per day.

The vitamin D nutritional status of premature infants was assessed by determining plasma 25-hydroxyvitamin D concentrations before and during supplementation with 500 IU vitamin D2 per day. Fifty-one samples were collected from 25 healthy infants fed breast milk and a vitamin D3 fortified formula. Gestational age was 32.2 +/- 2.4 weeks (mean +/- 1 SD). 25-hydroxyvitamin D levels before supplementation correlated well with maternal values (r = 0.81). The infants' mean plasma concentration increased from 30.6 +/- 13.7 nmol/l (mean +/- 1 SD) after birth to 46.3 +/- 10.5 nmol/l after 9 +/- 1 days (p less than 0.0025), and to 65.3 +/- 16.6 nmol/l after 37 +/- 10 days of vitamin D2 treatment (p less than 0.0005). 25-hydroxyvitamin D2 and 25-hydroxyvitamin D3 were determined separately, and it appeared that the rise was accounted for by the D2 fraction while 25-hydroxyvitamin D3 concentrations were unchanged. The results demonstrate that vitamin D2 is well absorbed and hydroxylated in the 25 position by premature infants free of associated disease, and that a supplementation of 500 IU per day in addition to breast milk and a regular vitamin D fortified formula is adequate to rapidly establish 25-hydroxyvitamin D levels within the normal adult range.