The claimEvidence C · limited
L-theanine = natural Xanax
The evidence
Its main effect is easing the jitters caffeine causes; there is no strong evidence for it on its own as an insomnia treatment.
The mechanism, in brief
The calm, unhurried feeling after a cup of tea is often credited to one amino acid in it: L-theanine. It is found almost only in the tea plant (Camellia sinensis), and the body does not use it to build protein, which is why it is called a non-protein amino acid.
Sources (2)
- Kakuda, T., Nozawa, A., Sugimoto, A., & Niino, H. (2002). Inhibition by theanine of binding of [3H]AMPA, [3H]kainate, and [3H]MDL 105,519 to glutamate receptors. Bioscience, Biotechnology, and Biochemistry, 66(12), 2683–2686. Rat cortical neurons: theanine bound the AMPA, kainate and NMDA-glycine sites, but far more weakly than glutamate; the abstract gives its IC50 as 80- to 30,000-fold less than that of L-glutamic acid, which in context means weaker binding (abstract, PMID 12596867).
- Scheid, L., Ellinger, S., Alteheld, B., Herholz, H., Ellinger, J., Henn, T., Helfrich, H.-P., & Stehle, P. (2012). Kinetics of L-theanine uptake and metabolism in healthy participants are comparable after ingestion of L-theanine via capsules and green tea. The Journal of Nutrition, 142(12), 2091-2096. Randomized crossover pharmacokinetic study: 12 participants took 100 mg L-theanine as capsules or as green tea (3 more took 50 and 200 mg capsules). Plasma L-theanine peaked 0.8 h after intake with both (24.3 and 26.5 µmol/L), AUC rose with dose, and theanine appeared to be hydrolyzed to ethylamine and glutamic acid; capsule and tea kinetics were comparable (abstract, PMID 23096008).