To the Editor:

I would like to thank the author for the commentary on our recent paper (1). A simple answer is that ‘nutritional requirements are not easily gauged in preterm infants.' There are many reasons for this. It remains unclear whether the reference fetus (2) or the empiric approach (3) should be used to estimate requirements. Irrespective, requirements will vary between the sexes (4) and between infants who are appropriately grown and those who are growth retarded. Requirements may also be altered by the clinical condition of the infant. In effect, one recommendation is unlikely to meet needs in all infants.

For the purpose of our study, protein requirements were based on the reference fetus (2) and current recommendations for the enterally-fed infant (5). To control for the effects of sex and differences in nutritional status a balanced cross-over design was used. The ‘sick' unstable infant primarily receives parenteral rather than enteral nutrition and, therefore, was not appropriate. The somewhat older clinically stable and enterally-fed infant was chosen, as a first step in better defining needs for growth in this nutritionally bereft group of infants.

The author states that “no data were provided on oral tolerance … nor on the appearance of gastrointestinal diseases.” No oral intolerance or gastrointestinal disturbance was noted with either formula. There was no reason to believe that oral tolerance or gastrointestinal disturbance would be a problem because previous studies have indicated excellent tolerance in preterm infants fed a completely hydrolysed whey protein preterm infant formula (6–8).

However, our study was not designed to examine oral tolerance and/or gastrointestinal disturbances such as necrotizing enterocolitis. The sample size was too small and the study period too short to make any definitive statement about these issues. All that could be said was that no evidence of protein overload; i.e., uremia and metabolic acidosis, was detected in any of the study infants. As stated in the manu-script, ‘a longer term randomized controlled trial is needed to address' such issues in a larger more representative group of infants (1).