The following references compile key experimental, clinical, and review studies examining the neurobiological and cognitive effects of L-theanine. The evidence spans its impact on neurotransmission, neuroplasticity, and electrophysiological correlates of cognition, as well as its modulatory role in stress reactivity, mood regulation, and sleep architecture. Collectively, these publications delineate the mechanistic and translational basis for L-theanine’s effects on neural function and cognitive performance across diverse populations.
L-Theanine is a key ingredient in Neuro FORMULA
1. Cognition & Memory
1: Anas Sohail A, Ortiz F, Varghese T, Fabara SP, Batth AS, Sandesara DP, Sabir A, Khurana M, Datta S, Patel UK. The Cognitive-Enhancing Outcomes of Caffeine and L-theanine: A Systematic Review. Cureus. 2021 Dec 30;13(12):e20828. doi: 10.7759/cureus.20828. PMID: 35111479; PMCID: PMC8794723.
2: Chen S, Kang J, Zhu H, Wang K, Han Z, Wang L, Liu J, Wu Y, He P, Tu Y, Li B. L-Theanine and Immunity: A Review. Molecules. 2023 May 1;28(9):3846. doi: 10.3390/molecules28093846. PMID: 37175254; PMCID: PMC10179891.
3: Nobre AC, Rao A, Owen GN. L-theanine, a natural constituent in tea, and its effect on mental state. Asia Pac J Clin Nutr. 2008;17 Suppl 1:167-8. PMID: 18296328.
4: Hidese S, Ogawa S, Ota M, Ishida I, Yasukawa Z, Ozeki M, Kunugi H. Effects of L-Theanine Administration on Stress-Related Symptoms and Cognitive Functions in Healthy Adults: A Randomized Controlled Trial. Nutrients. 2019 Oct 3;11(10):2362. doi: 10.3390/nu11102362. PMID: 31623400; PMCID: PMC6836118.
5: Owen GN, Parnell H, De Bruin EA, Rycroft JA. The combined effects of L-theanine and caffeine on cognitive performance and mood. Nutr Neurosci. 2008 Aug;11(4):193-8. doi: 10.1179/147683008X301513. PMID: 18681988.
6: Williams JL, Everett JM, D’Cunha NM, Sergi D, Georgousopoulou EN, Keegan RJ, McKune AJ, Mellor DD, Anstice N, Naumovski N. The Effects of Green Tea Amino Acid L-Theanine Consumption on the Ability to Manage Stress and Anxiety Levels: a Systematic Review. Plant Foods Hum Nutr. 2020 Mar;75(1):12-23. doi: 10.1007/s11130-019-00771-5. PMID: 31758301.
7: Türközü D, Şanlier N. L-theanine, unique amino acid of tea, and its metabolism, health effects, and safety. Crit Rev Food Sci Nutr. 2017 May 24;57(8):1681-1687. doi: 10.1080/10408398.2015.1016141. PMID: 26192072.
8: Li MY, Liu HY, Wu DT, Kenaan A, Geng F, Li HB, Gunaratne A, Li H, Gan RY. L-Theanine: A Unique Functional Amino Acid in Tea (Camellia sinensis L.) With Multiple Health Benefits and Food Applications. Front Nutr. 2022 Apr 4;9:853846. doi: 10.3389/fnut.2022.853846. PMID: 35445053; PMCID: PMC9014247.
9: Kimura K, Ozeki M, Juneja LR, Ohira H. L-Theanine reduces psychological and physiological stress responses. Biol Psychol. 2007 Jan;74(1):39-45. doi: 10.1016/j.biopsycho.2006.06.006. Epub 2006 Aug 22. PMID: 16930802.
10: Sarris J, Byrne GJ, Cribb L, Oliver G, Murphy J, Macdonald P, Nazareth S, Karamacoska D, Galea S, Short A, Ee C, Birling Y, Menon R, Ng CH. L-theanine in the adjunctive treatment of generalized anxiety disorder: A double-blind, randomised, placebo-controlled trial. J Psychiatr Res. 2019 Mar;110:31-37. doi: 10.1016/j.jpsychires.2018.12.014. Epub 2018 Dec 8. PMID: 30580081.
11: Saeed M, Khan MS, Kamboh AA, Alagawany M, Khafaga AF, Noreldin AE, Qumar M, Safdar M, Hussain M, Abd El-Hack ME, Chao S. L-theanine: an astounding sui generis amino acid in poultry nutrition. Poult Sci. 2020 Nov;99(11):5625-5636. doi: 10.1016/j.psj.2020.07.016. Epub 2020 Aug 6. PMID: 33142480; PMCID: PMC7647716.
12: Baba Y, Inagaki S, Nakagawa S, Kaneko T, Kobayashi M, Takihara T. Effects of l-Theanine on Cognitive Function in Middle-Aged and Older Subjects: A Randomized Placebo-Controlled Study. J Med Food. 2021 Apr;24(4):333-341. doi: 10.1089/jmf.2020.4803. Epub 2021 Mar 22. PMID: 33751906; PMCID: PMC8080935.
13: Sharma E, Joshi R, Gulati A. l-Theanine: An astounding sui generis integrant in tea. Food Chem. 2018 Mar 1;242:601-610. doi: 10.1016/j.foodchem.2017.09.046.Epub 2017 Sep 12. PMID: 29037735.
14: Kahathuduwa CN, Wakefield S, West BD, Blume J, Dassanayake TL, Weerasinghe VS, Mastergeorge A. Effects of L-theanine-caffeine combination on sustained attention and inhibitory control among children with ADHD: a proof-of-concept neuroimaging RCT. Sci Rep. 2020 Aug 4;10(1):13072. doi: 10.1038/s41598-020-70037-7. PMID: 32753637; PMCID: PMC7403383.
15: Giesbrecht T, Rycroft JA, Rowson MJ, De Bruin EA. The combination of L-theanine and caffeine improves cognitive performance and increases subjective alertness. Nutr Neurosci. 2010 Dec;13(6):283-90. doi: 10.1179/147683010X12611460764840. PMID: 21040626.
16: Qui NH. Immune-boosting role of L-theanine in broiler poultry production under stress conditions. Open Vet J. 2022 Mar-Apr;12(2):250-255. doi: 10.5455/OVJ.2022.v12.i2.13. Epub 2022 Apr 16. PMID: 35603064; PMCID: PMC9109851.
17: White DJ, de Klerk S, Woods W, Gondalia S, Noonan C, Scholey AB. Anti- Stress, Behavioural and Magnetoencephalography Effects of an L-Theanine-Based Nutrient Drink: A Randomised, Double-Blind, Placebo-Controlled, Crossover Trial. Nutrients. 2016 Jan 19;8(1):53. doi: 10.3390/nu8010053. PMID: 26797633; PMCID: PMC4728665.
18: Dashwood R, Visioli F. l-theanine: From tea leaf to trending supplement – does the science match the hype for brain health and relaxation? Nutr Res. 2025 Feb;134:39-48. doi: 10.1016/j.nutres.2024.12.008. Epub 2025 Jan 2. PMID: 39854799.
19: Nematizadeh M, Ghorbanzadeh H, Moghaddam HS, Shalbafan M, Boroon M, Keshavarz-Akhlaghi AA, Akhondzadeh S. L-theanine combination therapy with fluvoxamine in moderate-to-severe obsessive-compulsive disorder: A placebo- controlled, double-blind, randomized trial. Psychiatry Clin Neurosci. 2023 Sep;77(9):478-485. doi: 10.1111/pcn.13565. Epub 2023 May 27. PMID: 37169515.
20: Moshfeghinia R, Sanaei E, Mostafavi S, Assadian K, Sanaei A, Ayano G. The effects of L-theanine supplementation on the outcomes of patients with mental disorders: a systematic review. BMC Psychiatry. 2024 Dec 4;24(1):886. doi: 10.1186/s12888-024-06285-y. PMID: 39633316; PMCID: PMC11616108.
21: Rizzo R, Prato A, Scerbo M, Saia F, Barone R, Curatolo P. Use of Nutritional Supplements Based on L-Theanine and Vitamin B6 in Children with Tourette Syndrome, with Anxiety Disorders: A Pilot Study. Nutrients. 2022 Feb 18;14(4):852. doi: 10.3390/nu14040852. PMID: 35215501; PMCID: PMC8875106.
22: Wang Q, Yu J, Lin W, Ahammed GJ, Wang W, Ma R, Shi M, Ge S, Mohamed AS, Wang L, Li Q, Li X. L-Theanine Metabolism in Tea Plants: Biological Functions and Stress Tolerance Mechanisms. Plants (Basel). 2025 Feb 6;14(3):492. doi: 10.3390/plants14030492. PMID: 39943054; PMCID: PMC11820798.
23: Yoneda Y. An L-Glutamine Transporter Isoform for Neurogenesis Facilitated by L-Theanine. Neurochem Res. 2017 Oct;42(10):2686-2697. doi: 10.1007/s11064-017-2317-6. Epub 2017 Jun 9. PMID: 28597057.
24: Uyanga VA, Oke EO, Amevor FK, Zhao J, Wang X, Jiao H, Onagbesan OM, Lin H. Functional roles of taurine, L-theanine, L-citrulline, and betaine during heat stress in poultry. J Anim Sci Biotechnol. 2022 Mar 10;13(1):23. doi: 10.1186/s40104-022-00675-6. PMID: 35264238; PMCID: PMC8908636.
25: Noah L, Morel V, Bertin C, Pouteau E, Macian N, Dualé C, Pereira B, Pickering G. Effect of a Combination of Magnesium, B Vitamins, Rhodiola, and Green Tea (L-Theanine) on Chronically Stressed Healthy Individuals-A Randomized, Placebo-Controlled Study. Nutrients. 2022 Apr 29;14(9):1863. doi: 10.3390/nu14091863. PMID: 35565828; PMCID: PMC9102162.
26: Shamabadi A, Fattollahzadeh-Noor S, Fallahpour B, A Basti F, Khodaei Ardakani MR, Akhondzadeh S. L-Theanine adjunct to risperidone in the treatment of chronic schizophrenia inpatients: a randomized, double-blind, placebo- controlled clinical trial. Psychopharmacology (Berl). 2023 Dec;240(12):2631-2640. doi: 10.1007/s00213-023-06458-9. Epub 2023 Sep 12. PMID: 37697164.
27: Lopes Sakamoto F, Metzker Pereira Ribeiro R, Amador Bueno A, Oliveira Santos H. Psychotropic effects of L-theanine and its clinical properties: From the management of anxiety and stress to a potential use in schizophrenia. Pharmacol Res. 2019 Sep;147:104395. doi: 10.1016/j.phrs.2019.104395. Epub 2019 Aug 11. PMID: 31412272.
28: Lin S, Chen Z, Chen T, Deng W, Wan X, Zhang Z. Theanine metabolism and transport in tea plants (Camellia sinensis L.): advances and perspectives. Crit Rev Biotechnol. 2023 May;43(3):327-341. doi: 10.1080/07388551.2022.2036692. Epub 2022 Apr 17. PMID: 35430936.
29: Mu W, Zhang T, Jiang B. An overview of biological production of L-theanine. Biotechnol Adv. 2015 May-Aug;33(3-4):335-42. doi: 10.1016/j.biotechadv.2015.04.004. Epub 2015 Apr 12. PMID: 25871834.
30: Bulman A, D’Cunha NM, Marx W, Turner M, McKune A, Naumovski N. The effects of L-theanine consumption on sleep outcomes: A systematic review and meta- analysis. Sleep Med Rev. 2025 Jun;81:102076. doi: 10.1016/j.smrv.2025.102076. Epub 2025 Feb 25. PMID: 40056718.