Enriched post-discharge formula versus term formula for bone strength in very low birth weight infants: a longitudinal pilot study

AIM: To initiate a longitudinal pilot study comparing the effect of nutrient-enriched post-discharge formula (PDF) with standard term formula (TF) on bone strength of very low birth weight (VLBW) infants in the first six months post-term. METHODS: Two matched groups of VLBW infants were randomly assigned to enriched PDF (n=10) or TF (n=10) at corrected age of 40 weeks. Anthropometric measurements of growth and measurements of bone speed of sound (SOS) indicating bone strength and bone turnover markers (bone-specific alkaline phosphatase and cross-linked carboxy terminal telopeptide of type I collagen) were taken at term and at three and six months corrected age. RESULTS: The anthropometric measurements of infants fed PDF and TF were comparable at three and six months corrected age. Bone SOS of the PDF group increased from 2760+/-113 m/s at term to 2877+/-90 m/s and 3032+/-60 m/s at three and six months corrected age, respectively (P<0.001). Likewise, bone SOS of the TF group increased from 2695+/-116 m/s at term to 2846+/-72 and 2978+/-83 m/s at three and six months, respectively (P<0.001). No statistically significant difference was found between the groups in terms of growth and bone SOS measurements. The levels of both bone turnover markers decreased significantly during the study period (P<0.001 for both groups). CONCLUSION: Feeding with PDF after term had no short-term beneficial effect on bone strength and bone turn-over of VLBW infants.