Synopsis

Source of validity: Scientific
Rating (out of 5): 2

L-Theanine is an amino acid commonly found in tea leaves, especially green tea. It is often marketed as a supplement to promote relaxation and reduce stress, effects that are thought to involve modulation of the GABA (gamma-aminobutyric acid) system, the brain’s primary inhibitory neurotransmitter pathway. Scientific studies in both animals and humans suggest that L-theanine can increase brain levels of GABA, as well as dopamine and serotonin, which may contribute to its calming effects (Kimura et al., 2007; Nathan et al., 2006). However, most of this evidence is preliminary, with limited clinical trials and small sample sizes. The direct mechanism through which L-theanine influences GABAergic activity is still not fully understood, though some research suggests it may increase GABA synthesis or release. Importantly, while L-theanine appears safe and has shown promise for anxiety and stress reduction, its efficacy specifically in supporting the GABA system in humans is rated as modest due to the paucity of large, well-controlled studies. As such, the use of theanine for GABA support is best described as scientifically plausible, but not yet robustly validated.

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