What is theanine?

L-theanine is a nonprotein amino acid found in green tea and often available as a supplement. It impacts the brain by modulating certain neurotransmitters, primarily those that are excitatory like glutamate. Theanine competes for receptors, generally having a calming effect and reducing overall levels of alertness. This makes it useful for tackling the jitteriness caused by caffeine, as well as for reducing stress and anxiety. It can be taken in doses ranging from 100 to 400 milligrams and is particularly potent in the hours before sleep to aid in relaxation and improve sleep quality.

However, if someone is prone to vivid dreams, night terrors, or sleepwalking, they should use theanine cautiously or avoid it entirely due to its potential to intensify these issues 1 2 3.