L-theanine occurs naturally in tea, a beverage regarded as a calming and comforting companion by people all over the world. Alongside caffeine and flavonoids, L-theanine is one of tea’s key components. Closely related structurally to the amino acid glutamine, L-theanine exerts its effects in the central nervous system (CNS) by binding to glutamate receptors. It has also been shown to upregulate the major CNS hormones serotonin and dopamine, as well as promoting activity of other amino acids such as glycine (1). A cup of black tea contains approximately 25mg of L-theanine (2), yet human studies demonstrating its positive effects tend to use larger doses of 200mg.
L-theanine may have relaxing and calming effects. In a single-blind group comparison of students, consumption of supplemented L-theanine lead to decreased reports of subjective stress (3). In low-stress conditions (that being the stresses of daily life as opposed to, for example, the stress of losing a family member), another study has shown increased self-reported relaxation (4). Here, L-theanine even outperformed benzodiazepines, which are well known and potent anti-anxiety pharmaceuticals.
Closely linked to its relaxation-promoting effects, L-theanine may also act as a mood booster. In a randomised controlled trial, participants supplementing with L-theanine scored lower on validated depression and anxiety scores when compared to placebo (5).
Overall, L-theanine at a supplemented dose may have relaxing and mood-enhancing properties. Those who already drink plenty of tea must not worry though, as several animal studies have shown no safety concerns even at very high doses of L-theanine (6,7).
Relaxation, Mood.
Amino acid analogue.
200mg once daily.
Occurs naturally in tea at lower doses.
Nathan PJ, Lu K, Gray M, Oliver C. The Neuropharmacology of L-Theanine(N-Ethyl-L-Glutamine). http://dx.doi.org/101080/J157v06n02_02 [Internet]. 2009 Jan [cited 2022 Aug 22];6(2):21–30. Available from: https://www.tandfonline.com/doi/abs/10.1080/J157v06n02_02
Keenan EK, Finnie MDA, Jones PS, Rogers PJ, Priestley CM. How much theanine in a cup of tea? Effects of tea type and method of preparation. Food Chem. 2011 Mar 15;125(2):588–94
Unno K, Tanida N, Ishii N, Yamamoto H, Iguchi K, Hoshino M, et al. Anti-stress effect of theanine on students during pharmacy practice: Positive correlation among salivary α-amylase activity, trait anxiety and subjective stress. Pharmacol Biochem Behav. 2013 Oct 1;111:128–35.
Lu K, Gray MA, Oliver C, Liley DT, Harrison BJ, Bartholomeusz CF, et al. The acute effects of L-theanine in comparison with alprazolam on anticipatory anxiety in humans. Hum Psychopharmacol. 2004 Oct 1;19(7):457–65.
Hidese S, Ogawa S, Ota M, Ishida I, Yasukawa Z, Ozeki M, et al. Effects of L-Theanine Administration on Stress-Related Symptoms and Cognitive Functions in Healthy Adults: A Randomized Controlled Trial. Nutrients [Internet]. 2019 Oct 1 [cited 2022 Aug 22];11(10). Available from: https://pubmed.ncbi.nlm.nih.gov/31623400/
Borzelleca JF, Peters D, Hall W. A 13-week dietary toxicity and toxicokinetic study with l-theanine in rats. Food Chem Toxicol [Internet]. 2006 Jul [cited 2022 Aug 22];44(7):1158–66. Available from: https://pubmed.ncbi.nlm.nih.gov/16759779/
(PDF) Suntheanine: A pure and safe L-theanine dietary supplement for relaxation and stress relief [Internet]. [cited 2022 Aug 22]. Available from: https://www.researchgate.net/publication/281757321_Suntheanine_A_pure_and_safe_L-theanine_dietary_supplement_for_relaxation_and_stress_relief
