In humans, a bolus intake of isolated L-theanine in doses
between 50 and 200 mg increased the alpha brain wave activity
detected by electroencephalography, indicating relaxation (11).
The ingestion of 200–400 mg isolated L-theanine reduced
self-reported anxiety and stress in healthy participants (7) and
schizophrenia patients (12), respectively. Furthermore, L-theanine
is reported to improve attention and cognitive performance