The threonine requirement of the normal infant

In studies designed to evaluate the threonine requirement of normal infants a synthetic diet was employed which provided nitrogen in the form of a mixture of 18 essential and non-essential amino acids, all as the natural Lisomers. It was found that infants would gain weight normally and exhibit every sign of health on such a diet, although a somewhat higher than average caloric intake was at times required. By graded reduction of the threonine intake, threonine being replaced by glycine, the minimum threonine requirement was determined. This was found to be approximately 60 mg per kilogram per day for infants between one and 6 months of age. A deficiency of threonine was associated with failure to gain weight and with impaired retention of nitrogen. There was increased loss of nitrogen in the urine, but no increased amino aciduria. Certain changes in the amino acid excretion pattern were observed, notably a decreased threonine excretion.