Bone mineralization and turnover in preterm infants at 8-12 years of age: The effect of early diet

Our previous studies raised two hypotheses: first that suboptimal early nut rition and second that human milk have enhancing effects on long-term bone mineralization. To test these hypotheses experimentally, we measured whole body and regional bone mineral content (BMC) and bone mineral density (BMD) , using dual-energy X-ray absorptiometry and single-photon absorptiometry, and bone turnover at 8-12 years in 244 preterm children (128 boys) who part icipated in a prospective randomized study of diet during the neonatal peri od. Dietary randomizations studied were: banked human milk (BBM, n = 87) ve rsus preterm formula (PTF, n = 96) as the sole diet or as a supplement to m other's expressed breast milk (EBM); PTF (n = 25) versus term formula (TF, n = 36) as sole diet. Ninety-five term children of the same age were also s tudied. First, preterm children were shorter and lighter than term children (height SD scores -0.49 (1.1) vs. +0.22 (0.9), weight SD scores -0.41 (1.2 ) vs. +0.38 (1.0)) and had significantly lower whole-body BMC than their pe ers; decrements were also evident at some regional sites. These differences disappeared after adjusting for bone area, body size, and pubertal status. Second, children previously randomized to BBM versus PTF or TF versus PTF showed no significant differences in anthropometry, BMC, BMD, or osteocalci n (OC). Third, there was no independent effect of the proportion of EBM on BMC, BMD, or OC and no interaction between randomized diet and the amount o f EBM received. Fourth, plasma OC was significantly higher in preterm child ren than in term children (12.4 vs. 11.0 ng/ml, p < 0.005) and in preterm c hildren who had received a low-nutrient (BBM/TF) as opposed to a high-nutri ent diet (PTF) during the neonatal period (12.9 vs. 11.9 ng/ml, p = 0.03). In conclusion, preterm children are shorter, lighter, and have lower bone m ass than their peers at age 8-12 years. The lower BMC is, however, appropri ate for the bone and body size achieved. Despite large differences in early mineral intake, early diet does not affect bone mass in preterm children, and fresh human milk has no specific effect. However, poor nutrition during the neonatal period may result in higher bone formation rates during child hood.