Does early nutrition program later bone health in preterm infants?

Preterm infants are at risk of metabolic bone disease (MBD) because of an inadequate mineral intake. Although infants with MBD are frequently asymptomatic during the neonatal period, we previously reported that MBD predicted reduced linear growth in infancy and midchildhood. Nevertheless, some studies suggest that preterm infants undergo catch-up growth in bone mineralization during infancy. To examine the hypothesis that early nutrition programs affect later bone health and peak bone mass, we studied 20-y-old subjects who were born preterm and who were randomly assigned to a diet during the neonatal period; the diets used varied markedly in nutrient and mineral content, and phosphate supplements were not provided. Despite large variations in early nutrient and mineral intakes (and the occurrence of MBD) during the neonatal period, the randomly assigned diets did not influence peak bone mass or turnover. However, the proportion of (unsupplemented) human milk in the neonatal diet was significantly positively associated with later whole-body bone size and mineral content. Compared with population reference data, preterm subjects were significantly shorter and had lower lumbar spine bone mineral density; the deficits were greatest in those born small for gestational age (ie, a birth weight <1250 g). The lack of effect of the randomly assigned diets on peak bone mass suggests that the observed deficits in height and lumbar spine bone mass may not be related to suboptimal early nutrient or mineral intake. The higher whole-body bone mass associated with human milk intake, despite its very low nutrient content, may instead reflect nonnutritive factors in breast milk. These findings are relevant to discussions on the mineral requirements of preterm infants.