The glutamic acid concentration in the plasma of fasting
participants was 20.7 6 6.2 mmol/L. After intake of 100 mg
L-theanine, the ethylamine and glutamic acid concentrations in
plasma increased (Fig. 2). Other proteinogenic amino acids
in plasma were not affected by time. For all amino acids,
including L-theanine, effects by the kind of treatment and time 3
treatment were not observed. The plasma kinetics of L-theanine,
ethylamine, and glutamic acid were comparable after both
treatments (Table 2).