L- theanine is the primary amino acid in tea leaves, and known for it’s calming affect. Although recent data shows it may also play an important role in immunity and prevention. Numerous cell and animal studies have proven that theanine plays an important role in reducing inflammation. Additionally, theanine may also help with nerve damage, gut health and prevention of tumors by regulating glutathione synthesis and the secretion of cytokine and neurotransmitters.
Theanine may also improve cognitive performance and enhance working memory. In a study from 2021, researchers found a single dose of theanine reduced the reaction to attention to tasks, and increased the number of correct answers while decreasing the number of omission errors in working memory tasks. Another randomized, placebo controlled, crossover, and double-blind trial shown significant improvements in overall mental health while reducing stress. Overall, depression, anxiety and sleep scores all decreased and cognitive function scores improved of 4 weeks of 200mg taken daily.
Citations:
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.
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.
Dassanayake TL, Kahathuduwa CN, Weerasinghe VS. L-theanine improves neurophysiological measures of attention in a dose-dependent manner: a double-blind, placebo-controlled, crossover study. Nutr Neurosci. 2022 Apr;25(4):698-708. doi: 10.1080/1028415X.2020.1804098. Epub 2020 Aug 11. PMID: 32777998.
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.
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.
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.