The effect of zinc supplementation on linear growth, body composition, and growth factors in preterm infants

Objective. The aim of our study was to evaluate the effect of zinc supplementation on linear growth, body composition, and growth factors in premature infants. Design. Thirty-six preterm infants (gestational age: 32.0 +/- 2.1 weeks, birth weight: 1704 +/- 364 g) participated in a longitudinal double-blind, randomized clinical trial. They were randomly allocated either to the supplemental (S) group fed with a standard term formula supplemented with zinc (final content 10 mg/L) and a small quantity of copper (final content 0.6 mg/L), or to the placebo group fed with the same formula without supplementation ( final content of zinc: 5 mg/L and copper: 0.4 mg/L), from 36 weeks postconceptional age until 6 months corrected postnatal age. At each evaluation, anthropometric variables and bioelectrical impedance were measured, a 3-day dietary record was collected, and a blood sample was taken. We analyzed serum levels of total alkaline phosphatase, skeletal alkaline phosphatase (sALP), insulin growth factor (IGF)-I, IGF binding protein-3, IGF binding protein-1, zinc and copper, and the concentrations of zinc in erythrocytes. Results. The S group had significantly higher zinc levels in serum and erythrocytes and lower serum copper levels with respect to the placebo group. We found that the S group had a greater linear growth ( from baseline to 3 months corrected age: Delta score deviation standard length: 1.32 +/- .8 vs .38 +/- .8). The increase in total body water and in serum levels of sALP was also significantly higher in the S group ( total body water: 3 months; corrected age: 3.8 +/- .5 vs 3.5 +/- .4 kg, 6 months; corrected age: 4.5 +/- .5 vs 4.2 +/- .4 kg; sALP: 3 months; corrected age: 140.2 +/- 28.7 vs 118.7 +/- 18.8 mug/L). Conclusions. Zinc supplementation has a positive effect on linear growth in premature infants.