L-Theanine is an amino acid that is found almost exclusively in tea and is responsible for the exotic taste of green tea. Considered a non-dietary, non-essential amino acid, clinical research has demonstrated that L-Theanine promotes an alert state of relaxation without drowsiness. Additional research suggests L-Theanine may help improve quality of sleep, learning performance, mental acuity, concentration, and help support the immune system. L-Theanine may also help reduce the negative side effects of caffeine. L-Theanine can be taken during the day to help reduce stress or in the evening before bed to help calm and quiet your mind so you can drift off to sleep.