L-theanine is an amino acid. No natural synthesis of this compound occurs in the human body, and it is not required for human survival. L-theanine can be found in nature in green tea, black tea, and some varieties of mushroom.
L-theanine may affect the levels of certain chemicals in the brain. Mood, sleep, and emotion are all impacted by neurotransmitters like serotonin and dopamine, and the stress hormone cortisol is also involved.
A change in the balance of these chemicals can change a person’s mood or stress levels.
Small studies and tests on animals have shown that L-theanine may offer a range of benefits. Although it has been deemed safe by experts, more robust studies on humans are needed to confirm its effectiveness.