A recently published study conducted by researchers at the University of Shizuoka’s School of Pharmaceutical Sciences confirmed that the amino acid L-theanine helped reduce anxiety and stress in fifth-year pharmacy students (Pharmacol Biochem Behav. 2013 Oct;111:128-35).
The single blind, placebo-controlled study looked at the effects of L-theanine on the stress response of 20 student who were assigned to practice in a hospital or drug store setting for 11 weeks. The students were given 200 mg of L-theanine (Suntheanine from Taiyo International) twice daily or a placebo for 17 days: one week to establish a baseline and the first 10 days of the program (as it is assumed those days are the most stressful). Researchers assessed stress markers, including the amount of the stress enzyme amylase present in saliva, an indicator of psychological stress, and the amount of sleep students got.
All participants reported feeling less stress at the end of their 11-week program, though the participants Suntheanine got more sleep and experienced less anxiety. Suntheanine does not cause grogginess and has no known side effects.