The amino acid requirements of man. IV. The rôle of leucine and phenylalanine.

The reader is again referred to the first paper of this series (1) for full information regarding the general methods employed in the‘conduct of the experiments, the techniques used in analyzing the foods and excreta, and the procedures involved in the preparation of the diets. In all experiments, the diets consisted of mixtures of highly purified amino acids; wafers composed of starch, sucrose, purified butter fat (l), corn oil, salts, and baking powder; and additional calories in the form of sucrose and butter fat as required by the subjects. The amino acids were always ingested as aqueous solutions flavored with filtered lemon juice, and usually sweetened to taste with known amounts of sucrose. The extra butter fat served as a spread for the wafers. One-third of the daily allotment of each dietary component was consumed at each meal. As explained in preceding papers (1, 2), the subjects were healthy male graduate students, most of whom were majoring in biochemistry and consequently were interested in the outcome of the experiments. In determining the qualitative rale of leucine and phenylalanine, two subjects were used in each type of amino acid deficiency. In order to conserve space, and because of the uniformity of the findings observed in