N-ethyl-L-glutamine or L-theanine is an amino acid analog structurally similar to L-glutamate, one of the primary excitatory neurotransmitters in the central nervous system (CNS).
L-theanine is found in green tea [1]. Apart from contributing to its umami flavor [2], this molecule has anti-oxidative [3], anti-inflammatory [4], neuroprotective [5], and anxiolytic [6] properties, among others. In its natural form, theanine found in tea leaves or mushrooms exists as the L-enantiomer (D-configuration merely possesses biological activities). In the tea tree, L-theanine is synthesized by theanine synthetase from glutamic acid and ethylamine in the roots. L-theanine is then transported through the blast and accumulates in tea leaves, representing more than 50% of the total free amino acids [7]. L-theanine is rapidly absorbed in the intestine when tea is ingested via sodium-coupled co-transporters. It then travels through the bloodstream to various tissues and organs and crosses the blood-brain barrier to reach the CNS [7,8].
L-theanine effects on neurotransmitters
Monoamines
Research on the effects of L-theanine on brain neurotransmitters is limited. However, a study found that L-theanine increased striatal dopamine release in rats, an effect mediated by NMDA receptor activation and inhibited by the NMDA receptor antagonist AP-5 [9].
Another study investigated its effects on monoamine levels in diverse brain regions in a rat depression model. L-theanine significantly increased the levels of serotonin, norepinephrine, and dopamine in the prefrontal cortex, nucleus accumbens, and hippocampus regions, while it only increased the levels of serotonin and dopamine in the striatum [10].
One study reported an increase in GABA or γ-aminobutyric acid levels in mice brains after L-theanine treatment. In this study, the convulsive effect of caffeine was inhibited by L-theanine, suggesting a possible GABA-related anti-convulsive action [11].
Neurotransmitter receptors
A study investigating the effects of L-theanine with magnesium reported increased expression of GABAergic, serotonergic, and glutamatergic receptors [12]. L-theanine has also been shown to activate GABA-A receptors directly [13]. In addition, L-theanine can interact with the AMPA, NMDA, and kainate receptors [14], the three ionotropic glutamate receptors of L-glutamate in the CNS. Finally, L-theanine possesses long-term inhibitory effects on glutamate release [15].
L-theanine benefits
L-theanine and neuroprotection
Many studies in animals reported the neuroprotective effects of L-theanine on ischemic neuronal cell death [16,17]. While its neuroprotective effects seem partly due to weak antagonism of AMPA and kainate receptors [14], L-theanine modulates extracellular glutamine levels through its action on glutamine transporters in astrocytes [15]. Additionally, L-theanine appears to promote neurogenesis. In a rat model of spinal cord injury, L-theanine was able to promote the recovery of behavioral motor function. This neuroprotective mechanism may be related to L-theanine's inhibition of post-traumatic oxidative reaction, neuroinflammation, and apoptosis [18].
In another study, L-theanine could repair the normal brain structure by downregulating inflammatory cytokines in a rat model of brain oxidative stress induced by Aroclor 1254 [19]. In addition, L-theanine could inhibit neuronal death by inhibiting oxidative damage and tau hyperphosphorylation in a mouse model of cadmium-induced brain injury [20].
L-theanine and neurodegenerative diseases
In a mouse model of cognitive impairment induced by klotho gene depletion, L-theanine could alleviate memory impairment. Its effect resulted from the up-regulation of JAK2/STAT3, M1 muscarinic cholinergic receptor, and ERK signaling [21].
In a rat model of Huntington’s disease (HD) induced by quinolinic acid, L-theanine administration reduced the observed pathological changes [22]. In another rat model of HD induced by 3-nitropropionic acid, L-theanine showed neuroprotective effects by preventing NO production and neurotransmitter changes in the striatum [23]. L-theanine combined with luteolin was able to prevent Alzheimer’s-like symptoms in rats injected with amyloid-β25–35 by improving hippocampal insulin signaling, norepinephrine metabolism, and reducing neuroinflammation [24]. L-theanine also alleviated memory impairment and protected hippocampal long-term potentiation in Alzheimer's mice by activating the dopamine D1/5 receptor-protein kinase A pathway [25].
In humans, a study from 2006 identified a correlation between the high consumption of green tea and a lower prevalence of cognitive impairment in Japanese subjects aged 70 years or more [26]. Daily consumption of PGTH-theanine over 12 months prevented cognitive decline in aged volunteers, with minimal side effects. Thus, theanine might have the potential for the prevention of cognitive dysfunction and dementia [8].
L-theanine and depression
Many studies reported the ability of lifestyle changes to reduce the risk of major depressive disorder (MDD) [27-30]. Interestingly, tea consumption showed a strong relationship with reduced MDD [31]. Most studies found a link between tea consumption and lower risks of depression. For example, a MEDIS study found that daily tea consumption had the lowest relative risk for depression among all the metrics measured, such as consumption of fish, meat, vegetables, legumes, age, education, and BMI among others [32]. The main hypotheses to explain tea's anti-depressive effects include reducing hypothalamic-pituitary-adrenal axis hyperactivity, decreasing inflammation, restoring monoaminergic signaling through gut microbiota activity, and enhancing neurogenesis and neuroplasticity [33].
For instance, L-theanine treatment in mice demonstrated that supplementation normalized hypothalamic-pituitary-adrenal axis hyperactivity induced by heat stress [34]. This normalization was accompanied by significantly reduced plasma glucocorticoids and adrenocorticotropin levels [34,35]. These findings suggest that L-theanine might participate in the communication between inflammatory cytokines and the hypothalamic-pituitary-adrenal axis. Other studies suggested that its antagonistic effect on glutamate may take part in this normalization. Indeed, L-theanine in the brain can reduce the release of glutamate from pre-synapse to the synaptic cleft [8], where glutamate can then be carboxylated into GABA, the brain’s main inhibitory neurotransmitter [36].
L-theanine and schizophrenia
Several studies reported symptom alleviation related to L-theanine treatment of schizophrenic patients. One specific study found that L-theanine treatment significantly improved both the positive and negative syndrome scale scores and sleep quality in patients with schizophrenia. Magnetic resonance spectroscopy findings suggest that L-theanine exerts its effects by stabilizing glutamatergic concentration in the schizophrenic brain [37].
L-theanine and anxiety
A recent systematic review evaluated the effects of L-theanine oral supplementation on stress and anxiety in randomized controlled clinical trials. Based on nine peer-reviewed articles, L-theanine supplementation of 200-400 mg/day appeared to reduce anxiety and stress [38]. However, another systematic review comparing the efficacy of medicinal herbs to treat anxiety reported that L-theanine showed no difference with placebo [39]. Consequently, more research is needed to investigate the effects and mechanisms of L-theanine to conclude its efficacy in anti-anxiety and stress reduction.
L-theanine and sleep
In mice, treatment with a combination of GABA and L-theanine had positive synergistic effects on sleep quality and total sleep time as compared to GABA or L-theanine alone [40].
In humans, several clinical trials reported beneficial effects of L-theanine treatment in different patient populations. For example, oral L-theanine efficacy was assessed in a randomized double-blinded placebo-controlled study. Cancer patients suffering from sleep disorders like insomnia were given 200 mg of L-theanine once daily for two weeks. Results show that L-theanine was significantly better than the placebo in improving sleep quantity and quality [41]. Another randomized double-blind, randomized, placebo-controlled clinical trial assessed a combination treatment of L-theanine and Lactium to improve sleep in adults. The results suggest that L-theanine and Lactium have beneficial effects on sleep duration and appropriate bedtime. Additionally, changes in the gut microbiota may explain the observed changes in sleep patterns [42]. A recent review discussed the effects of tea components, including L-theanine, in regulating sleep via the immune system, neuroendocrine pathway, and gut microbiota [43].
L-theanine and cognition
Several experimental cross-over studies on healthy participants assessed the cognitive effects of L-theanine combined with caffeine. Apart from raising systolic blood pressure, several studies reported that L-theanine combined with caffeine was able to enhance attention as measured by an attention-switching task [44,45]. In addition, L-theanine and caffeine treatment shortened response time and increased accuracy in another attention-switching task [46]. Another study highlighted that L-theanine only presented beneficial effects on accuracy in a behavioral test when combined with caffeine [47]. Finally, L-theanine and caffeine were favorable in a test with seven subtractions in terms of reaction time, numerical working memory, and visual information processing [48]. The improvements in cognitive tasks observed in these studies were consistently attributed to the combined presence of both caffeine and L-theanine, likely due to the synergistic effects of both substances.
L-theanine and immunoregulation
Oral supplementation of L-theanine and cystine can alleviate the effects caused by high-intensity exercise in athletes; it prevents excessive inflammation and reduces muscle damage and immunosuppression [49]. L-theanine combined with cystine can also increase glutathione levels, restore natural killer cell activity, and enhance the immune response to prevent infectious diseases [50]. In addition, L-theanine participates in the reduction of interleukin-10, which has positive effects in restoring the helper T lymphocytes (Th) 1/Th2 balance disrupted after intense exercise [51]. Finally, L-theanine can partially protect against colds and flu as demonstrated by two randomized, double-blind, placebo-controlled trials by enhancing the gamma, and delta T cell function and promoting interferon-gamma secretion [52,53].
Conclusion
L-theanine, a compound found in tea leaves, exhibits numerous beneficial biological properties. It directly influences neurotransmitters and their receptors in the CNS, offering neuroprotective effects and positively impacting attention, cognition, and sleep. Additionally, L-theanine has an immunoregulatory role, further highlighting its wide-ranging therapeutic potential.
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References
[1] Nathan, P.J., Lu, K., Gray, M. and Oliver, C. (2006) The neuropharmacology of L-theanine(N-ethyl-L-glutamine): a possible neuroprotective and cognitive enhancing agent. Journal of Herbal Pharmacotherapy, 6, 21–30.
[2] Rogers, P.J., Smith, J.E., Heatherley, S.V. and Pleydell-Pearce, C.W. (2007) Time for tea: mood, blood pressure and cognitive performance effects of caffeine and theanine administered alone and together. Psychopharmacology, 195, 569–77. https://doi.org/10.1007/s00213-007-0938-1
[3] Li, C., Yan, Q., Tang, S., Xiao, W. and Tan, Z. (2018) L-Theanine Protects H9C2 Cells from Hydrogen Peroxide-Induced Apoptosis by Enhancing Antioxidant Capability. Medical Science Monitor, 24, 2109–18. https://doi.org/10.12659/MSM.907660
[4] Wang, Z., Zhang, L., Li, Z., Yu, Y., Yang, L., Zhang, P. et al. (2021) Alterations of endotoxin distribution across different biofluids and relevant inflammatory responses by supplementing L-theanine in dairy cows during heat stress. Animal Nutrition, 7, 1253–7. https://doi.org/10.1016/j.aninu.2021.03.012
[5] Takeshima, M., Miyazaki, I., Murakami, S., Kita, T. and Asanuma, M. (2016) L-Theanine protects against excess dopamine-induced neurotoxicity in the presence of astrocytes. Journal of Clinical Biochemistry and Nutrition, 59, 93–9. https://doi.org/10.3164/jcbn.16-15
[6] Wise, L.E., Premaratne, I.D., Gamage, T.F., Lichtman, A.H., Hughes, L.D., Harris, L.S. et al. (2012) l-theanine attenuates abstinence signs in morphine-dependent rhesus monkeys and elicits anxiolytic-like activity in mice. Pharmacology Biochemistry and Behavior, 103, 245–52. https://doi.org/10.1016/j.pbb.2012.08.008
[7] Chen, S., Kang, J., Zhu, H., Wang, K., Han, Z., Wang, L. et al. (2023) L-Theanine and Immunity: A Review. Molecules, 28, 3846. https://doi.org/10.3390/molecules28093846
[8] Kakuda, T. (2011) Neuroprotective effects of theanine and its preventive effects on cognitive dysfunction. Pharmacological Research, 64, 162–8. https://doi.org/10.1016/j.phrs.2011.03.010
[9] Yokogoshi, H., Kobayashi, M., Mochizuki, M. and Terashima, T. (1998) Effect of theanine, r-glutamylethylamide, on brain monoamines and striatal dopamine release in conscious rats. Neurochemical Research, 23, 667–73. https://doi.org/10.1023/A:1022490806093
[10] Shen, M., Yang, Y., Wu, Y., Zhang, B., Wu, H., Wang, L. et al. (2019) L‐theanine ameliorate depressive‐like behavior in a chronic unpredictable mild stress rat model via modulating the monoamine levels in limbic–cortical–striatal–pallidal–thalamic‐circuit related brain regions. Phytotherapy Research, 33, 412–21. https://doi.org/10.1002/ptr.6237
[11] Kimura, R. and Murata, T. (1971) Influence of Alkylamides of Glutamic Acid and Related Compounds on the Central Nervous System. I. Central Depressant Effect of Theanine. Chemical and Pharmaceutical Bulletin, 19, 1257–61. https://doi.org/10.1248/cpb.19.1257
[12] Dasdelen, M.F., Er, S., Kaplan, B., Celik, S., Beker, M.C., Orhan, C. et al. (2022) A Novel Theanine Complex, Mg-L-Theanine Improves Sleep Quality via Regulating Brain Electrochemical Activity. Frontiers in Nutrition, 9, 874254. https://doi.org/10.3389/fnut.2022.874254
[13] Egashira, N., Hayakawa, K., Osajima, M., Mishima, K., Iwasaki, K., Oishi, R. et al. (2007) Involvement of GABAA Receptors in the Neuroprotective Effect of Theanine on Focal Cerebral Ischemia in Mice. Journal of Pharmacological Sciences, 105, 211–4. https://doi.org/10.1254/jphs.SCZ070901
[14] Kakuda, T., Nozawa, A., Sugimoto, A. and Niino, H. (2002) Inhibition by Theanine of Binding of [ 3 H]AMPA, [ 3 H]Kainate, and [ 3 H]MDL 105,519 to Glutamate Receptors. Bioscience, Biotechnology, and Biochemistry, 66, 2683–6. https://doi.org/10.1271/bbb.66.2683
[15] Kakuda, T., Hinoi, E., Abe, A., Nozawa, A., Ogura, M. and Yoneda, Y. (2008) Theanine, an ingredient of green tea, inhibits [ 3 H]glutamine transport in neurons and astroglia in rat brain. Journal of Neuroscience Research, 86, 1846–56. https://doi.org/10.1002/jnr.21637
[16] Kakuda, T., Yanase, H., Utsunomiya, K., Nozawa, A., Unno, T. and Kataoka, K. (2000) Protective effect of γ-glutamylethylamide (theanine) on ischemic delayed neuronal death in gerbils. Neuroscience Letters, 289, 189–92. https://doi.org/10.1016/S0304-3940(00)01286-6
[17] Egashira, N., Hayakawa, K., Mishima, K., Kimura, H., Iwasaki, K. and Fujiwara, M. (2004) Neuroprotective effect of γ-glutamylethylamide (theanine) on cerebral infarction in mice. Neuroscience Letters, 363, 58–61. https://doi.org/10.1016/j.neulet.2004.03.046
[18] Yang, C.-C., Chang, K.-C., Wang, M.-H., Tseng, H.-C., Soung, H.-S., Fang, C.-H. et al. (2020) l-Theanine improves functional recovery after traumatic spinal cord injury in rats. Journal of the Formosan Medical Association, 119, 1405–14. https://doi.org/10.1016/j.jfma.2019.11.009
[19] Sumathi, T., Asha, D., Nagarajan, G., Sreenivas, A. and Nivedha, R. (2016) l-Theanine alleviates the neuropathological changes induced by PCB (Aroclor 1254) via inhibiting upregulation of inflammatory cytokines and oxidative stress in rat brain. Environmental Toxicology and Pharmacology, 42, 99–117. https://doi.org/10.1016/j.etap.2016.01.008
[20] Ben, P., Zhang, Z., Zhu, Y., Xiong, A., Gao, Y., Mu, J. et al. (2016) l -Theanine attenuates cadmium-induced neurotoxicity through the inhibition of oxidative damage and tau hyperphosphorylation. NeuroToxicology, 57, 95–103. https://doi.org/10.1016/j.neuro.2016.09.010
[21] Nguyen, B.T., Sharma, N., Shin, E.-J., Jeong, J.H., Lee, S.H., Jang, C.-G. et al. (2019) Theanine attenuates memory impairments induced by klotho gene depletion in mice. Food & Function, 10, 325–32. https://doi.org/10.1039/C8FO01577E
[22] Jamwal, S., Singh, S., Gill, J.S. and Kumar, P. (2017) L-theanine prevent quinolinic acid induced motor deficit and striatal neurotoxicity: Reduction in oxido-nitrosative stress and restoration of striatal neurotransmitters level. European Journal of Pharmacology, 811, 171–9. https://doi.org/10.1016/j.ejphar.2017.06.016
[23] Jamwal, S. and Kumar, P. (2017) L-theanine, a Component of Green Tea Prevents 3-Nitropropionic Acid (3-NP)-Induced Striatal Toxicity by Modulating Nitric Oxide Pathway. Molecular Neurobiology, 54, 2327–37. https://doi.org/10.1007/s12035-016-9822-5
[24] Park, S., Kim, D.S., Kang, S. and Kim, H.J. (2018) The combination of luteolin and l-theanine improved Alzheimer disease–like symptoms by potentiating hippocampal insulin signaling and decreasing neuroinflammation and norepinephrine degradation in amyloid-β–infused rats. Nutrition Research, 60, 116–31. https://doi.org/10.1016/j.nutres.2018.09.010
[25] Zhu, G., Yang, S., Xie, Z. and Wan, X. (2018) Synaptic modification by L-theanine, a natural constituent in green tea, rescues the impairment of hippocampal long-term potentiation and memory in AD mice. Neuropharmacology, 138, 331–40. https://doi.org/10.1016/j.neuropharm.2018.06.030
[26] Kuriyama, S., Hozawa, A., Ohmori, K., Shimazu, T., Matsui, T., Ebihara, S. et al. (2006) Green tea consumption and cognitive function: a cross-sectional study from the Tsurugaya Project. The American Journal of Clinical Nutrition, 83, 355–61. https://doi.org/10.1093/ajcn/83.2.355
[27] Kang, E. and Lee, J. (2010) A Longitudinal Study on the Causal Association Between Smoking and Depression. Journal of Preventive Medicine and Public Health, 43, 193. https://doi.org/10.3961/jpmph.2010.43.3.193
[28] Sullivan, L.E., Fiellin, D.A. and O’Connor, P.G. (2005) The prevalence and impact of alcohol problems in major depression: A systematic review. The American Journal of Medicine, 118, 330–41. https://doi.org/10.1016/j.amjmed.2005.01.007
[29] Schachter, J., Martel, J., Lin, C.-S., Chang, C.-J., Wu, T.-R., Lu, C.-C. et al. (2018) Effects of obesity on depression: A role for inflammation and the gut microbiota. Brain, Behavior, and Immunity, 69, 1–8. https://doi.org/10.1016/j.bbi.2017.08.026
[30] Dinas, P.C., Koutedakis, Y. and Flouris, A.D. (2011) Effects of exercise and physical activity on depression. Irish Journal of Medical Science, 180, 319–25. https://doi.org/10.1007/s11845-010-0633-9
[31] Dong, X., Yang, C., Cao, S., Gan, Y., Sun, H., Gong, Y. et al. (2015) Tea consumption and the risk of depression: A meta-analysis of observational studies. Australian & New Zealand Journal of Psychiatry, 49, 334–45. https://doi.org/10.1177/0004867414567759
[32] Masana, M.F., Haro, J.M., Mariolis, A., Piscopo, S., Valacchi, G., Bountziouka, V. et al. (2018) Mediterranean diet and depression among older individuals: The multinational MEDIS study. Experimental Gerontology, 110, 67–72. https://doi.org/10.1016/j.exger.2018.05.012
[33] Rothenberg, D.O. and Zhang, L. (2019) Mechanisms Underlying the Anti-Depressive Effects of Regular Tea Consumption. Nutrients, 11, 1361. https://doi.org/10.3390/nu11061361
[34] Wang, D., Cai, M., Wang, T., Zhao, G., Huang, J., Wang, H. et al. (2018) Theanine supplementation prevents liver injury and heat shock response by normalizing hypothalamic-pituitaryadrenal axis hyperactivity in mice subjected to whole body heat stress. Journal of Functional Foods, 45, 181–9. https://doi.org/10.1016/j.jff.2018.04.001
[35] Wang, D., Gao, Q., Zhao, G., Kan, Z., Wang, X., Wang, H. et al. (2018) Protective Effect and Mechanism of Theanine on Lipopolysaccharide-Induced Inflammation and Acute Liver Injury in Mice. Journal of Agricultural and Food Chemistry, 66, 7674–83. https://doi.org/10.1021/acs.jafc.8b02293
[36] Inoue, K., Miyazaki, Y., Unno, K., Min, J.Z., Todoroki, K. and Toyo’oka, T. (2016) Stable isotope dilution HILIC‐MS/MS method for accurate quantification of glutamic acid, glutamine, pyroglutamic acid, GABA and theanine in mouse brain tissues. Biomedical Chromatography, 30, 55–61. https://doi.org/10.1002/bmc.3502
[37] Ota, M., Wakabayashi, C., Sato, N., Hori, H., Hattori, K., Teraishi, T. et al. (2015) Effect of l -theanine on glutamatergic function in patients with schizophrenia. Acta Neuropsychiatrica, 27, 291–6. https://doi.org/10.1017/neu.2015.22
[38] Williams, J.L., Everett, J.M., D’Cunha, N.M., Sergi, D., Georgousopoulou, E.N., Keegan, R.J. et al. (2020) The Effects of Green Tea Amino Acid L-Theanine Consumption on the Ability to Manage Stress and Anxiety Levels: a Systematic Review. Plant Foods for Human Nutrition, 75, 12–23. https://doi.org/10.1007/s11130-019-00771-5
[39] Zhang, W., Yan, Y., Wu, Y., Yang, H., Zhu, P., Yan, F. et al. (2022) Medicinal herbs for the treatment of anxiety: A systematic review and network meta-analysis. Pharmacological Research, 179, 106204. https://doi.org/10.1016/j.phrs.2022.106204
[40] Kim, S., Jo, K., Hong, K.-B., Han, S.H. and Suh, H.J. (2019) GABA and l -theanine mixture decreases sleep latency and improves NREM sleep. Pharmaceutical Biology, 57, 64–72. https://doi.org/10.1080/13880209.2018.1557698
[41] Kurdi, M.S., As, A., Ladhad, D.A., Mitragotri, M.V. and Baiju, A. (2024) Comparison Between Efficacy of Oral Melatonin and Oral L-theanine in Improving Sleep in Cancer Patients Suffering From Insomnia: A Randomised Double-blinded Placebo-controlled Study. Indian Journal of Palliative Care, 30, 176–81. https://doi.org/10.25259/IJPC_89_2023
[42] Lim, S.E., Kim, H.S., Lee, S., Kang, E.Y., Lim, J.-H., Kim, B.-Y. et al. (2024) Dietary supplementation with Lactium and L-theanine alleviates sleep disturbance in adults: a double-blind, randomized, placebo-controlled clinical study. Frontiers in Nutrition, 11, 1419978. https://doi.org/10.3389/fnut.2024.1419978
[43] Wei, Y., Xu, J., Miao, S., Wei, K., Peng, L., Wang, Y. et al. (2023) Recent advances in the utilization of tea active ingredients to regulate sleep through neuroendocrine pathway, immune system and intestinal microbiota. Critical Reviews in Food Science and Nutrition, 63, 7598–626. https://doi.org/10.1080/10408398.2022.2048291
[44] Giesbrecht, T., Rycroft, J.A., Rowson, M.J. and De Bruin, E.A. (2010) The combination of L-theanine and caffeine improves cognitive performance and increases subjective alertness. Nutritional Neuroscience, 13, 283–90. https://doi.org/10.1179/147683010X12611460764840
[45] Einöther, S.J.L., Martens, V.E.G., Rycroft, J.A. and De Bruin, E.A. (2010) l-Theanine and caffeine improve task switching but not intersensory attention or subjective alertness. Appetite, 54, 406–9. https://doi.org/10.1016/j.appet.2010.01.003
[46] Owen, G.N., Parnell, H., De Bruin, E.A. and Rycroft, J.A. (2008) The combined effects of L-theanine and caffeine on cognitive performance and mood. Nutritional Neuroscience, 11, 193–8. https://doi.org/10.1179/147683008X301513
[47] Kelly, S.P., Gomez-Ramirez, M., Montesi, J.L. and Foxe, J.J. (2008) L-Theanine and Caffeine in Combination Affect Human Cognition as Evidenced by Oscillatory alpha-Band Activity and Attention Task Performance. The Journal of Nutrition, 138, 1572S-1577S. https://doi.org/10.1093/jn/138.8.1572S
[48] Haskell, C.F., Kennedy, D.O., Milne, A.L., Wesnes, K.A. and Scholey, A.B. (2008) The effects of l-theanine, caffeine and their combination on cognition and mood. Biological Psychology, 77, 113–22. https://doi.org/10.1016/j.biopsycho.2007.09.008
[49] Murakami, S., Kurihara, S., Titchenal, C.A. and Ohtani, M. (2010) Suppression of exercise-induced neutrophilia and lymphopenia in athletes by cystine/theanine intake: a randomized, double-blind, placebo-controlled trial. Journal of the International Society of Sports Nutrition, 7, 23. https://doi.org/10.1186/1550-2783-7-23
[50] Kawada, S., Kobayashi, K., Ohtani, M. and Fukusaki, C. (2010) Cystine and Theanine Supplementation Restores High-Intensity Resistance Exercise-Induced Attenuation of Natural Killer Cell Activity in Well-Trained Men. Journal of Strength and Conditioning Research, 24, 846–51. https://doi.org/10.1519/JSC.0b013e3181c7c299
[51] Juszkiewicz, A., Glapa, A., Basta, P., Petriczko, E., Żołnowski, K., Machaliński, B. et al. (2019) The effect of L-theanine supplementation on the immune system of athletes exposed to strenuous physical exercise. Journal of the International Society of Sports Nutrition, 16, 7. https://doi.org/10.1186/s12970-019-0274-y
[52] Rowe, C.A., Nantz, M.P., Bukowski, J.F. and Percival, S.S. (2007) Specific Formulation of Camellia sinensis Prevents Cold and Flu Symptoms and Enhances γδ T Cell Function: A Randomized, Double-Blind, Placebo-Controlled Study. Journal of the American College of Nutrition, 26, 445–52. https://doi.org/10.1080/07315724.2007.10719634
[53] Kurihara, S., Hiraoka, T., Akutsu, M., Sukegawa, E., Bannai, M. and Shibahara, S. (2010) Effects of -Cystine and -Theanine Supplementation on the Common Cold: A Randomized, Double-Blind, and Placebo-Controlled Trial. Journal of Amino Acids, 2010, 1–7. https://doi.org/10.4061/2010/307475
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