Abstract
Plasma urea nitrogen, ammonia and amino acid concentrations and urinary nitrogen excretion were measured in 10 males after ingestion of one-third of the recommended dietary allowance (RDA) for protein as (trial 1) an L-amino acid mixture, (trial 2) cottage cheese, (trial 3) a combination of cottage cheese and L-amino acids. Mean changes in total essential plasma amino acids were significantly greater at 15 minutes for trials 1 (314 ± 223 μmol 1−1) and 3 (306 ± 294 umol l−1) vs trial 2 (7 ± 114 umol l−1). Mean changes in plasma urea nitrogen from fasting differed significantly between trials 1 and 3 at 15 minutes (0.51 vs −0.79 mol l−1), 45 minutes (0.26 vs − 0.57 mmol l−1) and 180 minutes (0.68 vs 0.08 mmol 1−1). Mean total change in plasma urea nitrogen concentrations over 3 hours was greater for trial 1 (3.38 mmol l−l) than for trial 3 (− 1.71 mmol l−1). The mean plasma ammonia concentration was significantly greater than fasting (14 pmol 1−1) at 120 minutes (38 μmol l−1) for trial 1 only; total change in plasma ammonia over 3 hours did not differ between trials. Urinary nitrogen excretion did not differ between trials. Utilization of amino acids as assessed by plasma urea nitrogen and ammonia concentrations and urinary nitrogen excretion does not appear to differ following ingestion of whole protein, L-amino acids or a combination of the two.
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