Magnesium balance studies in premature and term infants

Background. The knowledge of magnesium requirements of premature infants is still very limited, although it is essential for the optimal composition o f suitable formulas. Aim of the study: The study concept was 1) to assess physiological magnesiu m balance data of healthy term infants and longitudinal results from formul a-fed premature infants and 2) to deduce conclusions on the magnesium conte nt of the formulas. Methods: Premature infants (n=14, birth weight less than or equal to 1500 g , gestational age less than or equal to 32 weeks) were studied in conventio nal balance trials with 1) a semi-elemental diet (A), 2) preterm infant for mula (B), and 3) infant formula (C). In addition, healthy term formula-fed (n=11, D) and breast-fed (n=14, E) infants were investigated. Analysis was performed by flame atomic absorption spectroscopy. Results: The median magnesium intake ranged between 4.84 mg/kg x d(-1) (bre ast-fed infants) and 16.33 mg/kg x d(-1) (premature infants). The term brea st-fed infants retained nearly as much magnesium as term formula-fed infant s (3.37 vs. 3.97 mg/kg x d(-1)), due to a low percental fecal and urinary e xcretion. A higher magnesium retention was observed in the premature group: A: 7.97 mg/kg x d(-1), B: 5.3 mg/kg x d(-1), 3.) C: 5.54 mg/kg x d(-1). Conclusion: In view of the high percental magnesium retention in formula-fe d premature infants, excessive supply should be avoided. The long-term effe cts of lower intakes have to be monitored.