Knowledge of the requirements for essential amino acids during infancy has been derived largely from short-term studies of weight gain and nitrogen balance of infants fed mixtures of 18 L-amino acids.1 As indicated by Holt and Snyderman in 1961,1 such studies are not necessarily predictive of the requirements for essential amino acids by infants fed whole proteins:
We do not regard these figures as final. We expect them to be modified as other investigators tackle this problem, as we hope they will do. All that can be said is that this is the best information we can muster today. Validity of our figures can be checked by comparing them with data on minimal intakes of amino acids observed on natural diets compatible with health. Such data do not give minimal requirements, but they indicate that requirement levels are not greater than that provided by the intake shown.
FOMON SJ, OWEN GM, THOMAS LN. Methionine, Valine And IsoleucineRequirements During Infancy: Growth and Nitrogen Balance Studies With Normal Fullterm Infants Receiving Soybean Protein. Am J Dis Child. 1964;108(5):487-493. doi:10.1001/archpedi.1964.02090010489007