Based on animal studies showing high in utero amino acid flux observed during the latter phase of gestation, Thureen et al have suggested the use of higher doses of amino acid supplementation in order to minimize growth restriction and improve outcomes of premature infants. However there are no large human trials that demonstrate that this approach promotes better growth or that it is safe. While small doses of amino acids may be inadequate to promote normal growth, high doses may lead to elevated serum amino acid levels and increase the occurrence of toxicity. Through the implementation of a multicenter, randomized trial and tandem mass spectrometry, the investigators propose to evaluate the effects of two distinct strategies of amino acid supplementation on serum amino acid profiles and growth of premature infants during the first 28 days of life.