L-theanine is a unique amino acid that is found almost exclusively in the tea plant (Camellia sinensis) and which has been used safely in Japan for decades. L-theanine has been shown to positively modify brain waves and the key neurotransmitters involved in mood, focus, and memory. L-theanine enhances the production of the neurotransmitters dopamine and serotonin, and also appears to play a role in the formation of GABA – a neurotransmitter that acts like a "brake" during times of runaway stress. L-theanine also enhances brain alpha-wave activity, a marker of relaxation. This effect has been observed to be most pronounced in individuals subjectively feeling the highest levels of stress.

A Japanese study of university students found that 200 mg of L-theanine led to increased brain alpha-waves and a subjective sense of relaxation. In the same study, L-theanine administration also caused a dose-dependent relaxed, yet alert, state of mind without sedation, beginning approximately 40 minutes after ingestion.

L-theanine can enhance the production of the neurotransmitters dopamine and serotonin, and it appears to play a role in the formation of GABA – a neurotransmitter that acts like a "brake" during times of runaway stress. L-theanine helps establish balance in the neurotransmitter system, resulting in improvements in the mental/emotional and physical disturbances resulting from being overly stressed.