Nitrogen requirement of amino acid mixture with maintenance energy in young men.

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Abstract
The effect of energy on N balance was examined in young men given amino acid mixture. The minimum amino acid N requirement for N equilibrium was determined together with the egg protein requirement. In experiment 1, the N sparing effect of energy was evaluated in 4 male students receiving diet containing an amino acid mixture and a constant N intake of 3.5 g N/day, which was equivalent to the N requirement with excess energy intake determined by Rose and Wixom. When the dietary energy supply was 45 kcal/kg, which is approximately the maintenance level, the mean N balance was negative, being -23.9 .+-. 9.3 mg N/kg. With an excess energy intake of 55 kcal/kg, the N balance improved significantly, being -6.1 .+-. 7.7 mg N/kg. In experiment 2, the N requirement of egg-pattern amino acid mixture for apparently zero balance was evaluated at maintenance energy intake in 28 Japanese young men and was compared with that of egg protein. After receiving standard diet, the subjects were given a semi-purified experimental diet containing egg-pattern amino acid mixture at N intake levels of 60, 75, 100 an 130 mg N/kg for 2 wk. Then all groups except the 60 mg N/kg group were given isonitrogenous egg protein diet for another week. Energy intake was kept constant at approximately the maintenance level of 44.4 .+-. 1.4 kcal/kg throughout the experiment. N balance was not significantly different in groups given egg-pattern amino acid mixture and intact egg protein in each nitrogen intake level. From regression analysis, the N requirement for N equilibrium of the amino acid mixture was calculated to be 110.1 .+-. 50.2 mg N/kg, which was not significantly different from the value of 88.4 .+-. 40.6 mg N/kg of egg protein. The total amino acid requirement estimated by Rose and Wixom was too low because they gave excess energy, and that there was no difference between the N requirement of egg protein and that of the corresponding amino acid mixture.