REQUIREMENTS FOR INDISPENSABLE AMINO-ACIDS IN ADULT HUMANS - LONGER-TERM AMINO-ACID KINETIC-STUDY WITH SUPPORT FOR THE ADEQUACY OF THE MASSACHUSETTS-INSTITUTE-OF-TECHNOLOGY AMINO-ACID REQUIREMENT PATTERN

Twenty young men received an L-amino acid diet, supplying 140 mg N . kg-1 . d-1 and patterned as in the Egg diet for 1 wk. and then for 3 wk either a pattern based on international recommendations (modified FAO diet; n = 7), our new amino acid requirement pattern (MIT diet; n = 7), or the egg pattern (Egg diet; n = 6). At the end of the initial week, at 1 and 3 wk with the three experimental diets, and after 3 d after return to the Egg diet, an 8-h continuous intravenous infusion with [1-C-13]leucine (3 h fast, 5 h fed while subjects received hourly meals supplying the equivalent of one-twelfth the daily intake) was conducted. After 3 wk with the different diets, mean daily leucine balances were lower (P < 0.01) with the FAO diet (-160 mumol . kg-1 . d-1) than with the MIT diet (-15 mumol . kg-1 . d-1). Together with changes in plasma amino acid profiles [eg, methionine increased (P < 0.05) during feeding with the FAO and Egg diets but not with the MIT diet; increased proline concentrations during the fed state (P < 0.05) with the FAO diet but not with the MIT or Egg diets] we interpret these findings to indicate that the FAO diet is not capable of maintaining amino acid homeostasis, as is the case with the MIT and Egg diets.