Nutritional balance studies in very-low-birth-weight infants: role of whey formula.

Although the optimal type and amount of protein for feeding very-low-birth-weight (VLBW) infants is not well defined, a protein composition with a whey protein to casein ratio of 60/40 is generally considered desirable. This study used the metabolic balance technique to compare nitrogen retention rates in 19 VLBW (less than 1,530 g) infants fed either an experimental whey protein-predominant formula (WPF) containing ultra filtered whey protein or a conventional casein-predominant formula (CPF) containing approximately 20% more protein and more minerals. Blood chemistries and anthropometric measurements were assessed serially. Although infants fed CPF received and retained more protein than infants fed WPF, nitrogen retentions were 73.1 and 74.5% of intake, respectively, and not different between the two feeding groups. The data suggest that proteins from either WPF or CPF are adequately utilized by VLBW infants. Although WPF permitted nitrogen retention rates similar to fetal accretion rates, CPF more nearly met estimated nitrogen requirements of the low-birth-weight infant. Infants fed WPF showed a more favorable course with respect to their metabolic acid-base status, characterized by normal buffer base concentrations and less predisposition to metabolic acidosis. We conclude that whey-predominant protein is preferable to casein-predominant protein in the diet of VLBW neonates because it may lessen the risk of metabolic acidosis and its potential adverse effects.