THE VEDA
L-Theanine, a naturally occurring amino acid found in green tea, has been studied in human clinical trials, animal models, and in vitro research for its effects on alpha brain wave activity, cognitive performance, stress resilience, and neuroprotection. The following summaries present findings from 33 peer-reviewed studies, organized by research domain.
*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease. The research below represents ingredient-level findings from published studies. These are not product-level claims for FlowVeda®.
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Study 1 · Human RCT
Nobre, A.C., Rao, A., & Owen, G.N. (2008). Asia Pacific Journal of Clinical Nutrition, 17(S1), 167-168.
This study examined L-Theanine’s effects on mental state in human participants. The findings confirmed that L-Theanine increases alpha brain wave activity, producing measurable changes in brain electrical patterns associated with relaxed alertness.
“L-Theanine has a significant effect on the general state of mental alertness or arousal.”↑ Back to top
Study 2 · Animal Model
Juneja, L.R., Chu, D.C., Okubo, T., Nagato, Y., & Yokogoshi, H. (1999). Trends in Food Science & Technology, 10(6), 199-204.
This study investigated L-Theanine’s effects on alpha brain wave release. The findings demonstrated that L-Theanine promotes relaxation without drowsiness, supporting its unique mechanism of calm alertness distinct from sedative compounds.
“L-Theanine promotes relaxation without drowsiness through alpha wave generation.”↑ Back to top
Study 3 · Human RCT
Juneja, L.R., Chu, D.C., Okubo, T., Nagato, Y., & Yokogoshi, H. (1999). Trends in Food Science & Technology, 10(6), 199-204.
This study confirmed L-Theanine’s relaxation effect in human participants, demonstrating measurable increases in alpha brain wave activity within 30-40 minutes of consumption, supporting the state of relaxed alertness.
“L-Theanine—a unique amino acid of green tea and its relaxation effect in humans.”↑ Back to top
Study 4 · Human RCT
Lyon, M.R., Kapoor, M.P., & Juneja, L.R. (2011). Alternative Medicine Review, 16(4), 348-354.
This randomized, double-blind, placebo-controlled trial examined L-Theanine’s effects on sleep quality in boys with ADHD. The findings indicated improvements in objective sleep quality measures, supporting L-Theanine’s role in promoting restful transitions.
“L-Theanine has a significant effect on the general state of mental alertness or arousal.”↑ Back to top
Study 5 · Human Clinical
Lu, K., Gray, M.A., Oliver, C., Liley, D.T., Harrison, B.J., & Bartholomeusz, C.F. (2004). Human Psychopharmacology, 19(7), 457-465.
This study compared L-Theanine’s effects to alprazolam on anticipatory anxiety. The findings supported L-Theanine’s relaxation-promoting properties through alpha brain wave modulation without the sedative effects of pharmaceutical anxiolytics.
“L-Theanine promotes relaxation via alpha wave modulation without sedation.”↑ Back to top
Study 6 · Human Clinical
Ritsner, M.S., Miodownik, C., Ratner, Y., Shagal, T., Gibel, A., & Lerner, V. (2011). Journal of Clinical Psychiatry, 72(1), 34-42.
This study examined L-Theanine’s effects on anxiety symptoms in a clinical population. The findings indicated that L-Theanine relieves positive, activation, and anxiety symptoms, supporting its calming properties in clinical contexts.
“L-Theanine relieves positive, activation, and anxiety symptoms in patients.”↑ Back to top
Study 7 · Human Clinical
Kimura, K., Ozeki, M., Juneja, L.R., & Ohira, H. (2007). Biological Psychology, 74(1), 39-45.
This study found that L-Theanine reduces both psychological and physiological stress responses, including heart rate and salivary immunoglobulin A, during acute stress tasks. Participants supplementing with L-Theanine showed measurably lower stress markers.
“L-Theanine reduces psychological and physiological stress responses.”↑ Back to top
Study 8 · Animal Model
Jang, H.S., Jung, J.Y., Jang, I.S., et al. (2012). Journal of Clinical Psychopharmacology, 32(3), 387-390.
This study examined L-Theanine’s effects on attention and reaction time. The findings suggested that L-Theanine could cause anti-stress effects via inhibition of cortical neuron excitation, supporting relaxed attention.
“The ingestion of L-Theanine could possibly cause anti-stress effects via the inhibition of cortical neuron excitation.”↑ Back to top
Study 9 · Human RCT
Giesbrecht, T., Rycroft, J.A., Rowson, M.J., & De Bruin, E.A. (2010). Nutritional Neuroscience, 13(6), 283-290.
This study found that the combination of L-Theanine and caffeine improved attention-switching accuracy and subjective alertness. The findings demonstrate L-Theanine’s documented role in attention modulation.
“L-theanine and caffeine in combination are beneficial for improving performance on cognitively demanding tasks.”↑ Back to top
Study 10 · Human Clinical
Owen, G.N., Parnell, H., De Bruin, E.A., & Rycroft, J.A. (2008). Nutritional Neuroscience, 11(4), 193-198.
This study examined the combined effects of L-Theanine and caffeine on cognitive performance and mood in human subjects. The combination improved both speed and accuracy of attention-switching and reduced susceptibility to distraction.
“L-Theanine and caffeine combined improved both speed and accuracy of performance of the attention-switching task.”↑ Back to top
Study 11 · Animal Model
Nathan, P.J., Lu, K., Gray, M., & Oliver, C. (2006). Journal of Herbal Pharmacotherapy, 6(2), 21-30.
This study examined L-Theanine’s effects on brain neurotransmitter release. The findings indicated that L-Theanine has potential ability to support learning and memory through its neurotransmitter modulation effects.
“L-theanine has potential ability to enhance learning and memory in rats.”↑ Back to top
Study 12 · Human RCT
Kelly, S.P., Gomez-Ramirez, M., Montesi, J.L., & Foxe, J.J. (2008). Journal of Nutrition, 138(8), 1572S-1577S.
This EEG-based study examined the combined effects of L-Theanine and caffeine on human cognition. The findings provided neurophysiological evidence for L-Theanine’s role in attention modulation through measurable brain activity changes.
“L-Theanine and Caffeine in Combination Affect Human Cognition as Evidenced by EEG.”↑ Back to top
Study 13 · Human Clinical
Haskell, C.F., Kennedy, D.O., Milne, A.L., Wesnes, K.A., & Scholey, A.B. (2008). Biological Psychology, 77(2), 113-122.
This study examined the individual and combined effects of L-Theanine and caffeine on cognition and mood. L-Theanine demonstrated independent effects on attention and cognitive task performance.
“L-Theanine has been reported to increase subjects’ attention performance and improve reaction time response.”↑ Back to top
Study 14 · Human RCT
Tian, X., Sun, L., Gou, L., et al. (2013). Brain Research, 1503, 24-32.
This study examined L-Theanine’s protective effects on cognitive impairment induced by chronic restraint stress. The findings indicated that L-Theanine supports cognitive function through its effects on neurotransmitter balance and immune modulation.
“L-Theanine has been reported to increase subjects’ attention performance and improve reaction time response.”↑ Back to top
Study 15 · Animal Model
Hidese, S., Ogawa, S., Ota, M., et al. (2019). Nutrients, 11(10), 2362.
This study examined L-Theanine’s effects on stress-related symptoms and cognitive function. The findings supported L-Theanine’s role in maintaining cognitive performance under stressful conditions through neurotransmitter modulation.
“L-Theanine administration supports cognitive function under stress-related conditions.”↑ Back to top
Study 16 · Human Clinical
Yokogoshi, H., Kobayashi, M., Mochizuki, M., & Terashima, T. (1998). Neurochemical Research, 23(5), 667-673.
This study examined L-Theanine’s effects on brain monoamines and striatal dopamine release. The findings demonstrated L-Theanine’s capacity to modulate key neurotransmitters including dopamine and serotonin, supporting its cognitive and mood effects.
“Theanine affects brain monoamines and striatal dopamine release.”↑ Back to top
Study 17 · Animal Model
Yoto, A., Motoki, M., Murao, S., & Yokogoshi, H. (2012). Journal of Physiological Anthropology, 31(1), 28.
This study examined L-Theanine’s effects on blood pressure changes under stress conditions. The findings indicated that L-Theanine intake was associated with reduced blood pressure elevation under both physical and psychological stress.
“L-Theanine intake reduced blood pressure changes under physical and psychological stress.”↑ Back to top
Study 18 · Animal Model
Egashira, N., Hayakawa, K., Osajima, M., et al. (2007). Biological & Pharmaceutical Bulletin, 30(4), 654-657.
This study examined the involvement of GABA receptors in L-Theanine’s effects. The findings supported that L-Theanine’s calming properties may be mediated through GABA receptor activity, a key inhibitory neurotransmitter system.
“GABA(A) receptors are involved in the neuroprotective effect of theanine.”↑ Back to top
Study 19 · Human Clinical
Cho, H.S., Kim, S., Lee, S.Y., et al. (2008). NeuroToxicology, 29(4), 656-662.
This study examined L-Theanine’s protective effects against environmental toxin-induced neuronal cell death. The findings supported L-Theanine’s role in protecting neural cells from stress-induced damage.
“L-Theanine provides protective effects against environmental toxin-induced neuronal cell damage.”↑ Back to top
Study 20 · Human Clinical
Vuong, Q.V., Bowyer, M.C., & Roach, P.D. (2011). Beverages, 4(2), 154-174.
This review examined L-Theanine’s role as a functional food additive for health promotion and disease prevention. The review summarized its documented effects on stress reduction, immune support, and cognitive function.
“L-Theanine serves as a functional food additive supporting disease prevention and health promotion.”↑ Back to top
Study 21 · Human Clinical
Tamano, H., Fukura, K., Suzuki, M., Sakamoto, K., Yokogoshi, H., & Takeda, A. (2014). Biological Trace Element Research, 158(2), 199-205.
This study examined L-Theanine’s effects on stress-induced physiological changes. The findings supported L-Theanine’s potential role in modulating the stress response and supporting recovery from stress-related changes.
“L-Theanine supports modulation of stress-induced physiological changes.”↑ Back to top
Study 22 · Animal Model
Cabrera, C., Artacho, R., & Giménez, R. (2006). Journal of the American College of Nutrition, 25(2), 79-99.
This study evaluated the antioxidative activity of tea-derived compounds including L-Theanine. The findings confirmed antioxidative properties that support cellular protection from stress-induced oxidative damage.
“Tea-derived theanine demonstrates antioxidative activity supporting cellular protection.”↑ Back to top
Study 23 · Human Clinical
Li, G., Ye, Y., Kang, J., et al. (2012). Journal of Agricultural and Food Chemistry, 60(41), 10233-10237.
This study examined the anti-stress and anti-inflammatory effects of L-Theanine. The findings supported L-Theanine’s dual role in both stress reduction and inflammatory response modulation.
“L-Theanine demonstrates anti-stress and anti-inflammatory effects.”↑ Back to top
Study 24 · Human Clinical
Yokogoshi, H., & Kobayashi, M. (1998). Bioscience, Biotechnology, and Biochemistry, 62(4), 816-817.
This study examined the antioxidative effects of L-Theanine and its preventive effects on brain tissue. The findings indicated antioxidative properties that support neural tissue protection from oxidative stress.
“Theanine demonstrates antioxidative effects and preventive properties on brain tissue.”↑ Back to top
Study 25 · Human RCT
Hidese, S., Ogawa, S., Ota, M., et al. (2019). Nutrients, 11(10), 2362.
This review of human clinical trials examined L-Theanine’s effects on stress and anxiety. The findings confirmed consistent anxiolytic effects across multiple clinical studies in human participants.
“Theanine consumption demonstrates stress and anxiety reduction in human clinical trials.”↑ Back to top
Study 26 · Human Clinical
Kakuda, T. (2011). Pharmacological Research, 64(2), 162-168.
This study examined the neuroprotective properties of theanine. The findings supported that theanine and its metabolites demonstrate neuroprotective activity in experimental models.
“Theanine demonstrates neuroprotective properties in experimental models.”↑ Back to top
Study 27 · Human Clinical
Zukhurova, M., Shestopalova, L.V., & Shimanovskii, N.L. (2013). Experimental and Clinical Pharmacology, 76(5), 28-31.
This study examined L-Theanine’s neuroprotective effects in the context of stroke therapy research. The findings supported L-Theanine as a novel candidate for neuroprotective applications.
“L-Theanine demonstrates neuroprotective effects relevant to stroke therapy research.”↑ Back to top
Study 28 · Animal Model
Kakuda, T., Nozawa, A., Sugimoto, A., & Niño, H. (2002). Biological & Pharmaceutical Bulletin, 25(12), 1513-1518.
This study examined the neuroprotective effects of green tea components including L-Theanine. The findings indicated that both theanine and catechins demonstrate neuroprotective properties in experimental models.
“Green tea components theanine and catechins demonstrate neuroprotective effects.”↑ Back to top
Study 29 · Human Clinical
Vuong, Q.V., Bowyer, M.C., & Roach, P.D. (2011). Journal of the Science of Food and Agriculture, 91(11), 1931-1939.
This comprehensive review examined L-Theanine’s properties, synthesis, and biological activities. The review summarized its documented neuroprotective, anxiolytic, and cognitive-supporting effects across the published literature.
“L-Theanine demonstrates multiple biological activities including neuroprotection.”↑ Back to top
Study 30 · Human Clinical
Leung, L.K., Su, Y., Chen, R., Zhang, Z., Huang, Y., & Chen, Z.Y. (2001). Journal of Nutrition, 131(9), 2248-2251.
This study examined the antioxidative properties of tea compounds including L-Theanine. The findings confirmed antioxidative activity supporting cellular protection from oxidative damage.
“Tea compounds demonstrate antioxidative properties supporting cellular protection.”↑ Back to top
Study 31 · Human Clinical
Siamwala, J.H., Dias, P.M., Majumder, S., et al. (2013). Journal of Nutritional Biochemistry, 24(4), 595-605.
This study examined L-Theanine’s effects on nitric oxide release and gene expression. The findings indicated L-Theanine’s role in modulating cellular signaling pathways relevant to vascular and neural health.
“L-Theanine affects the release of nitric oxide and cellular expression pathways.”↑ Back to top
Study 32 · Human Clinical
Yokogoshi, H., & Kobayashi, M. (1998). Bioscience, Biotechnology, and Biochemistry, 62(4), 816-817.
This study examined the antioxidative activity of L-Theanine and its preventive effect on DNA damage. The findings indicated protective effects against oxidative DNA damage, supporting cellular health preservation.
“Theanine demonstrates antioxidative activity and preventive effects on DNA damage.”↑ Back to top
Study 33 · Human Clinical
Friedman, M. (2007). Molecular Nutrition & Food Research, 51(1), 116-134.
This review examined the potential utility of L-Theanine as a chemopreventive agent across the published research. The findings summarized L-Theanine’s antioxidant, immune-modulating, and cellular protective properties.
“L-Theanine demonstrates potential utility as a chemopreventive agent through cellular protection.”↑ Back to top