Kinetics of Amino Acid Release from Proteins

To understand and predict the ultimate effects of various proteins on the organs and systems of the body during physical exertion, it is necessary to have an understanding of the fate of amino acids contained in proteins after ingestion.

With this goal in mind, L.M. Burke and colleagues conducted two crossover clinical trials (RCTs) involving untrained and trained individuals.

In the first study (n = 15, untrained individuals after overnight fasting), 20 grams of protein from different sources (milk, soy milk, meat, eggs, liquid dietary supplements) were administered.

In the second study (n = 10, trained endurance athletes, fasting participants), 20 grams of protein were consumed during rest and after a 60-minute submaximal exercise. Biochemical indicators of amino acid concentrations in the plasma, including Total Amino Acids (TAA), Essential Amino Acids (EAA), Branched-Chain Amino Acids (BCAA), and leucine, were analyzed at various time intervals. Despite the fact that the area under the curve “time-concentration of TAA” was similar when different protein sources were ingested, the peaks of BCAA, TAA, EAA, and leucine concentrations were reached significantly faster after milk consumption (Figure 1), which further confirms the advantages of whey proteins in terms of supporting muscle activity.

Pharmacokinetic parameters for soy protein were significantly worse compared to other protein sources.

When analyzing changes in amino acid concentrations in trained individuals after consuming 20 grams of protein, the changes shown in Figure 2 were observed.

As seen from the data presented in Figures 1 and 2, despite differences in the dynamics and concentration peaks for overall amino acids, no significant differences were observed in the most important amino acids (BCAA, particularly leucine) when protein was consumed during the resting period or after exercise.

Figure 1.

Dynamics of amino acid concentrations in plasma (μg×mL-1, y-axis) over three hours (min, x-axis) after oral intake of 20 grams of proteins in various dietary supplements (citation: Burke L.M. et al., 2012): BCAA – branched-chain amino acids (leucine, isoleucine, valine), TAA – total amino acids, EAA – essential amino acids in general.

Figure 2.

Dynamics of amino acid concentrations in plasma (μg×mL-1, y-axis) over three hours (min, x-axis) after oral intake of 20 grams of protein in trained individuals after exercise or during rest (citation: Burke L.M. et al., 2012): BCAA – branched-chain amino acids (leucine, isoleucine, valine), TAA – total amino acids, EAA – essential amino acids in general.

Dynamics of amino acid concentrations in plasma ideal pharma peptide.