Randomised controlled trial of vitamin D supplementation on bone density and biochemical indices in preterm infants

Aims-To test the hypothesis that a vitamin D dose of 200 IU/kg, maximum 400 IU/day, given to preterm infants will maintain normal vitamin D status and will result in as high a bone mineral density as that attained with the re commended dose of 960 IU/day. Methods-Thirty nine infants of fewer than 33 weeks of gestational age were randomly allocated to receive vitamin D 200 IU/kg of body weight/day up to a maximum of 400 IU/day or 960 IU/day until 3 months old. Vitamin D metabol ites, bone mineral content and density were determined by dual energy x-ray absorptiometry, and plasma ionised calcium, plasma alkaline phosphatase, a nd intact parahormone measurements were used to evaluate outcomes. Results-The 25 hydroxy vitamin D concentrations tended to be higher in infa nts receiving 960 IU/day, but the differences did not reach significance at any age. There was no difference between the infants receiving low or high vitamin D dose in bone mineral content nor in bone mineral density at 3 an d 6 months corrected age, even after taking potential risk factors into acc ount. Conclusions-A vitamin D dose of 200 IU/kg of body weight/day up to a maximu m of 400 IU/day maintains normal vitamin D status and as good a bone minera l accretion as the previously recommended higher dose of 960 IU/day. Vitami n D is a potent hormone which affects organs other than bone and should not be given in excess to preterm infants.