Theanine is the amino acid critical for its calming influence on cognitive function. It crosses the blood-brain barrier to help establish a state of relaxation while maintaining alertness. Upon exposure to the brain, it stimulates production of gamma-aminobutyric acid (GABA), the chemical produced by the brain that blocks excitatory stimuli that contribute to stress.

Theanine follows a similar pathway to prescription drugs from the benzodiazepine group (Valium, Xanax), without the risk of harmful side effects or addiction. Studies have also shown ʟ‑theanine to encourage alpha wave activity associated with a state of serenity and mental clarity. It also insulates the nervous system from stress that can cause dangerous spikes in blood pressure, and carbohydrate cravings that result in accumulation of stubborn belly fat.