Nutrient retention in preterm infants fed standard infant formulas.

Our purpose was to compare nitrogen, mineral, and zinc balance in preterm infants fed standard infant formulas, Similac With Iron and Similac With Whey + Iron. Nitrogen and magnesium balances were similar during both feeds, and met estimated fetal requirements. Infants absorbed and retained (milligrams per kilogram per day) more calcium, phosphorus, and zinc when fed Similac With Iron. However, retention of calcium, phosphorus (both formulas), and zinc (Similac With Whey + Iron) was inadequate to meet estimated fetal requirements. These findings are important in the rapidly growing preterm infant, who is already at risk for the development of rickets and zinc deficiency and may be fed either formula on discharge from the newborn nursery.