**5.1 Measurements of plasma levels of amino acids in old and young men**

**Table 1** shows the background of participants. There was no difference on energy intake between young and old men. Young men take more lipids and old men take more carbohydrate.

**Table 2** shows plasma levels of amino acids of young and old men. Plasma levels of nonessential amino acids were higher in old men than young men. No differences were shown in plasma levels of total amino acids, and total essential and branched amino acids between young and old men.

Levels of phenylalanine, tyrosine, alanine, A-aminobutyric acid, citrulline, cysteine, glutamic acid, ornithine, and taurine were higher in old men, and serine were higher in young men.
