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Theanine (L-theanine) is a powerful neuroenhancer often heralded as a relaxation enhancing tool similar to meditation. The compound improves alpha brain waves, which is a pattern in the brain correlated with the highest activity and mental capacity [2].

Beyond these benefits, theanine is helping improve upon the positive aspects of caffeine while mitigating the negative issues such as anxiety, increased blood pressure, and diminished sleep quality [1]. Theanine has also been found to have positive effects on brain chemistry [1].

Other Common Names



Top Benefits

Supports cognitive function
Supports relaxed mood
Supports stress resilience
Supports sleep
Supports general immune health


What Is Theanine?

Theanine is one of the most ubiquitous compounds that few people are aware they ingest. As a main psychoactive constituent of tea leaves, this amino acid has been improving brain health for thousands of years across the globe. According to studies in the past few decades, this specific nonessential amino acid is one of the most useful tools for people using smart drugs.

Theanine is a calming amino acid that naturally occurs in green tea. It is used as a smart drug because it supports focused attention, mental alertness, and a calm, relaxed sense of mental energy. Theanine is often used with caffeine because the combination supports task switching, accuracy, and focus. However, theanine is entirely effective on its own, especially as a stress adaptogen (reducing adverse effects of stress on the body). Theanine promotes alpha brain waves (α-waves), which are thought of as a marker of relaxation [3]. This brain state also reduces the perception of stress. Theanine has a few other lesser-known functional actions. Theanine can be broken down into glutamate, which is a building block for glutamatergic signaling, i.e., the glutamate-GABA pathway, and for glutathione, an antioxidant used for detoxification. Theanine, because of another metabolite, primes specialized immune cells—gamma delta T cells—that help the immune system respond more efficiently to new antigens and have enhanced immune memory. The best dietary sources of theanine are green and black tea (made from Camellia sinensis). Theanine comprises up to 50% of total amino acids in tea leaves.


Marco’s Grounds Theanine Sourcing

Our theanine is extracted from organic green tea leaves. Marco’s Grounds theanine is sourced from family-owned organic farms and is non-GMO, gluten-free, and vegan.


Theanine Dosing Principles and Rationale

Theanine has been studied clinically over a relatively wide range of doses, with the most common range being 100-400 mg. Evidence suggests a threshold response (see Marco’s Grounds Dosing Philosophy) when theanine is given by itself, i.e., the best responses occur when it’s dosed within a range as opposed to more being better. That said, the dose of theanine used in Marco’s Grounds was based on assuming the user also drinks three to four coffees a day (upper scale of users). Thus, the formulation was calibrated to provide soothing effects with these quantities of caffeine in mind. Theanine tends to work perfectly when put in a ratio of 2:1 compared to caffeine or theobromine. When used in combination with GABA before bedtime for supporting sleep, it might be dosed at as little as 20% of the GABA dose, i.e., 1:5 ratio. Following an oral dose, the amount of theanine in the brain increase within the first hour, i.e., it’s able to cross the blood-brain barrier [4], so in general, theanine has a relatively quick onset. It is often experienced within 30-45 minutes of ingestion. Shall the user not drink coffee or ingest caffeine sources, theanine still works as a stress reducer and focus increaser.


Theanine Key Mechanisms

Brain function

Supports attention [3–5]

Supports memory [6–9]

Supports learning [10]

Supports executive function [6, 11]

Supports faster reaction times [5]

Supports alpha brain waves (α-waves are associated with relaxation, selective attention, and mental alertness) [3, 5, 12–15]

Supports hippocampal activity [16]

Supports dopamine signaling [17–23]

Supports serotonin signaling [23]

Supports GABA levels in the brain [23]

Binds to glutamate receptors (with low affinity)[24–26]

Supports hippocampal neurogenesis [8]

Supports brain-derived neurotrophic factor (BDNF) [8, 26, 27]

Supports neuroprotective functions[9, 10, 28–30]

Mood and stress

Supports a calm/relaxed mood [6, 10, 11, 15, 16, 31–33]

Supports a positive mental-emotional bias [6, 11]

Modulates psychological and physiological stress responses [35]

Supports healthy behavioral and cognitive responses to stress [28, 36]

Reduces fight or flight nervous system activity (i.e., promotes relaxation response) [35]


Supports sleep efficiency and quality [6, 11, 37, 38]

Counters some of caffeine’s effects on deep sleep [39]


Supports innate immunity [40–42]

Supports adaptive immunity [40, 41, 42]

Supports gamma delta T cell function [44, 45]

Modulates immune signaling [40, 42]

Gastrointestinal function

Supports gut microbiota [47]

Supports amino acid absorption [48]

Healthy aging and longevity

Pro-longevity (Caenorhabditis elegans) [49]


Caffeine in cognitive performance [50–52]

GABA for supporting sleep quality [54]

L-Cysteine in support of general immune health [55–561]

Green tea extracts in support of general immune health [62, 63]​


Theanine Deep Dive


  1. Kimura, K., Ozeki, M., Juneja, L. R., & Ohira, H. (2007). L-Theanine reduces psychological and physiological stress responses. Biological psychology, 74(1), 39–45.
  2. Nobre, A. C., Rao, A., & Owen, G. N. (2008). L-theanine, a natural constituent in tea, and its effect on mental state. Asia Pacific journal of clinical nutrition, 17 Suppl 1, 167–168.
  3. Juneja, L. R., Chu, D. C., Okubo, T., Nagato, Y., & Yokogoshi, H. (1999). L-theanine—a unique amino acid of green tea and its relaxation effect in humans. Trends in Food Science & Technology, 10(6-7), 199-204.
  4. Terashima, T., Takido, J., & Yokogoshi, H. (1999). Time-dependent changes of amino acids in the serum, liver, brain and urine of rats administered with theanine. Bioscience, biotechnology, and biochemistry, 63(4), 615-618.
  5. Higashiyama, A., Htay, H. H., Ozeki, M., Juneja, L. R., & Kapoor, M. P. (2011). Effects of l-theanine on attention and reaction time response. Journal of Functional Foods, 3(3), 171-178.
  6. Hidese, S., Ota, M., Wakabayashi, C., Noda, T., Ozawa, H., Okubo, T., & Kunugi, H. (2017). Effects of chronic l-theanine administration in patients with major depressive disorder: an open-label study. Acta neuropsychiatrica, 29(2), 72-79.
  7. Park, S. K., Jung, I. C., Lee, W. K., Lee, Y. S., Park, H. K., Go, H. J., … & Rho, S. S. (2011). A combination of green tea extract and l-theanine improves memory and attention in subjects with mild cognitive impairment: a double-blind placebo-controlled study. Journal of medicinal food, 14(4), 334-343.
  8. Takeda, A., Sakamoto, K., Tamano, H., Fukura, K., Inui, N., Suh, S. W., … & Yokogoshi, H. (2011). Facilitated neurogenesis in the developing hippocampus after intake of theanine, an amino acid in tea leaves, and object recognition memory. Cellular and molecular neurobiology, 31(7), 1079-1088.
  9. Kim, T. I., Lee, Y. K., Park, S. G., Choi, I. S., Ban, J. O., Park, H. K., … & Hong, J. T. (2009). l-Theanine, an amino acid in green tea, attenuates β-amyloid-induced cognitive dysfunction and neurotoxicity: reduction in oxidative damage and inactivation of ERK/p38 kinase and NF-κB pathways. Free Radical Biology and Medicine, 47(11), 1601-1610.
  10. Unno, K., Fujitani, K., Takamori, N., Takabayashi, F., Maeda, K. I., Miyazaki, H., … & Hoshino, M. (2011). Theanine intake improves the shortened lifespan, cognitive dysfunction and behavioural depression that are induced by chronic psychosocial stress in mice. Free Radical Research, 45(8), 966-974.
  11. Hidese, S., Ogawa, S., Ota, M., Ishida, I., Yasukawa, Z., Ozeki, M., & Kunugi, H. (2019). Effects of L-Theanine Administration on Stress-Related Symptoms and Cognitive Functions in Healthy Adults: A Randomized Controlled Trial. Nutrients, 11(10), 2362.
  12. Song, C. H., Jung, J. H., Oh, J. S., & Kim, K. S. (2003). Effects of theanine on the release of brain alpha wave in adult males. Korean Journal of Nutrition, 36(9), 918-923.
  13. Gomez-Ramirez, M., Higgins, B. A., Rycroft, J. A., Owen, G. N., Mahoney, J., Shpaner, M., & Foxe, J. J. (2007). The deployment of intersensory selective attention: a high-density electrical mapping study of the effects of theanine. Clinical neuropharmacology, 30(1), 25-38.
  14. Owen, G. N., Parnell, H., De Bruin, E. A., & Rycroft, J. A. (2008). The combined effects of L-theanine and caffeine on cognitive performance and mood. Nutritional neuroscience, 11(4), 193-198.
  15. White, D. J., De Klerk, S., Woods, W., Gondalia, S., Noonan, C., & Scholey, A. B. (2016). Anti-stress, behavioural and magnetoencephalography effects of an L-theanine-based nutrient drink: a randomised, double-blind, placebo-controlled, crossover trial. Nutrients, 8(1), 53.
  16. Ogawa, S., Ota, M., Ogura, J., Kato, K., & Kunugi, H. (2018). Effects of L-theanine on anxiety-like behavior, cerebrospinal fluid amino acid profile, and hippocampal activity in Wistar Kyoto rats. Psychopharmacology, 235(1), 37-45.
  17. Yokogoshi, H., Kobayashi, M., Mochizuki, M., & Terashima, T. (1998). Effect of theanine, r-glutamylethylamide, on brain monoamines and striatal dopamine release in conscious rats. Neurochemical research, 23(5), 667-673.
  18. Yamada, T., Terashima, T., Okubo, T., Juneja, L. R., & Yokogoshi, H. (2005). Effects of theanine, r-glutamylethylamide, on neurotransmitter release and its relationship with glutamic acid neurotransmission. Nutritional Neuroscience, 8(4), 219-226.
  19. Yamada, T., Terashima, T., Kawano, S., Furuno, R., Okubo, T., Juneja, L. R., & Yokogoshi, H. (2009). Theanine, γ-glutamylethylamide, a unique amino acid in tea leaves, modulates neurotransmitter concentrations in the brain striatum interstitium in conscious rats. Amino Acids, 36(1), 21.
  20. Yao, J., Shen, X. N., Shen, H., & Wu, M. (2012). Effects of theanine on monoamine neurotransmitters and related genes in cerebral ischemia-reperfusion. Zhonghua yu Fang yi xue za zhi [Chinese Journal of Preventive Medicine], 46(7), 635-639.
  21. Shen, M., Yang, Y., Wu, Y., Zhang, B., Wu, H., Wang, L., … & Chen, J. (2019). L‐theanine ameliorate depressive‐like behavior in a chronic unpredictable mild stress model via modulating the monoamine levels in limbic–cortical–striatal–pallidal–thalamic‐circuit related brain regions. Phytotherapy Research, 33(2), 412-421.
  22. Zhu, G., Yang, S., Xie, Z., & Wan, X. (2018). Synaptic modification by L-theanine, a natural constituent in green tea, rescues the impairment of hippocampal long-term potentiation and memory. Neuropharmacology, 138, 331-340.
  23. Nathan, P. J., Lu, K., Gray, M., & Oliver, C. (2006). The neuropharmacology of L-theanine (N-ethyl-L-glutamine) a possible neuroprotective and cognitive enhancing agent. Journal of Herbal Pharmacotherapy, 6(2), 21-30.
  24. Yokogoshi, H., Kobayashi, M., Mochizuki, M., & Terashima, T. (1998). Effect of theanine, r-glutamylethylamide, on brain monoamines and striatal dopamine release. Neurochemical research, 23(5), 667-673.
  25. Kakuda, T., Nozawa, A., Sugimoto, A., & NIINO, H. (2002). Inhibition by theanine of binding of [3H] AMPA,[3H] kainate, and [3H] MDL 105,519 to glutamate receptors. Bioscience, biotechnology, and biochemistry, 66(12), 2683-2686.
  26. Wakabayashi, C., Numakawa, T., Ninomiya, M., Chiba, S., & Kunugi, H. (2012). Behavioral and molecular evidence for psychotropic effects in L-theanine. Psychopharmacology, 219(4), 1099-1109.
  27. Miodownik, C., Maayan, R., Ratner, Y., Lerner, V., Pintov, L., Mar, M., … & Ritsner, M. S. (2011). Serum levels of brain-derived neurotrophic factor and cortisol to sulfate of dehydroepiandrosterone molar ratio associated with clinical response to L-theanine as augmentation of antipsychotic therapy in schizophrenia and schizoaffective disorder patients. Clinical neuropharmacology, 34(4), 155-160.
  28. Tian, X., Sun, L., Gou, L., Ling, X., Feng, Y., Wang, L., … & Liu, Y. (2013). Protective effect of l-theanine on chronic restraint stress-induced cognitive impairments. Brain research, 1503, 24-32.
  29. Sumathi, T., Asha, D., Nagarajan, G., Sreenivas, A., & Nivedha, R. (2016). L-Theanine alleviates the neuropathological changes induced by PCB (Aroclor 1254) via inhibiting upregulation of inflammatory cytokines and oxidative stress. Environmental toxicology and pharmacology, 42, 99-117.
  30. Takeshima, M., Miyazaki, I., Murakami, S., Kita, T., & Asanuma, M. (2016). l-Theanine protects against excess dopamine-induced neurotoxicity in the presence of astrocytes. Journal of clinical biochemistry and nutrition, 16-15.
  31. Lu, K., Gray, M. A., Oliver, C., Liley, D. T., Harrison, B. J., Bartholomeusz, C. F., … & Nathan, P. J. (2004). The acute effects of L‐theanine in comparison with alprazolam on anticipatory anxiety in humans. Human Psychopharmacology: Clinical and Experimental, 19(7), 457-465.
  32. Ritsner, M. S., Miodownik, C., Ratner, Y., Shleifer, T., Mar, M., Pintov, L., & Lerner, V. (2011). L-theanine relieves positive, activation, and anxiety symptoms in patients with schizophrenia and schizoaffective disorder: an 8-week, randomized, double-blind, placebo-controlled, 2-center study. Journal of Clinical Psychiatry, 72(1), 34.
  33. Unno, K., Tanida, N., Ishii, N., Yamamoto, H., Iguchi, K., Hoshino, M., … & Yamada, H. (2013). Anti-stress effect of theanine on students during pharmacy practice: Positive correlation among salivary α-amylase activity, trait anxiety and subjective stress. Pharmacology Biochemistry and Behavior, 111, 128-135.
  34. Yoto, A., Motoki, M., Murao, S., & Yokogoshi, H. (2012). Effects of L-theanine or caffeine intake on changes in blood pressure under physical and psychological stresses. Journal of physiological anthropology, 31(1), 28.
  35. Jang, H. S., Jung, J. Y., Jang, I. S., Jang, K. H., Kim, S. H., Ha, J. H., … & Lee, M. G. (2012). L-theanine partially counteracts caffeine-induced sleep disturbances. Pharmacology Biochemistry and Behavior, 101(2), 217-221.
  36. Tamano, H., Fukura, K., Suzuki, M., Sakamoto, K., Yokogoshi, H., & Takeda, A. (2013). Preventive effect of theanine intake on stress-induced impairments of hippocamapal long-term potentiation and recognition memory. Brain research bulletin, 95, 1-6.
  37. OZEKI, M., Juneja, L. R., & SHIRAKAWA, S. (2004). 1-2 The Effects of Theanine on Sleep with Physiological Evaluation Using Actigraph (Proceedings of the 50th Meeting of Japan Society of Physiological Anthropology). Journal of physiological anthropology and applied human science, 23(2), 58.
  38. Lyon, M. R., Kapoor, M. P., & Juneja, L. R. (2011). The effects of L-theanine (Suntheanine®) on objective sleep quality in boys with attention deficit hyperactivity disorder (ADHD): a randomized, double-blind, placebo-controlled clinical trial. Alternative medicine review, 16(4), 348.
  39. Jang, H. S., Jung, J. Y., Jang, I. S., Jang, K. H., Kim, S. H., Ha, J. H., … & Lee, M. G. (2012). L-theanine partially counteracts caffeine-induced sleep disturbances in rats. Pharmacology Biochemistry and Behavior, 101(2), 217-221.
  40. Juszkiewicz, A., Glapa, A., Basta, P., Petriczko, E., Żołnowski, K., Machaliński, B., … & Skarpańska-Stejnborn, A. (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(1), 7.
  41. Mingsheng, L., Jianhong, Z., Min, L., Qihua, G., & Chengping, H. (2014). Theanine improves the function of dendritic cells via the downregulation of cyclooxygenase-2 expression. Chinese Medical Journal, 127(8), 1545-1549.
  42. Kim, N. H., Jeong, H. J., & Kim, H. M. (2012). Theanine is a candidate amino acid for pharmacological stabilization of mast cells. Amino acids, 42(5), 1609-1618.
  43. Li, C., Tong, H., Yan, Q., Tang, S., Han, X., Xiao, W., & Tan, Z. (2016). L-Theanine improves immunity by altering TH2/TH1 cytokine balance, brain neurotransmitters, and expression of phospholipase C. Medical science monitor: international medical journal of experimental and clinical research, 22, 662.
  44. Kamath, A. B., Wang, L., Das, H., Li, L., Reinhold, V. N., & Bukowski, J. F. (2003). Antigens in tea-beverage prime human Vγ2Vδ2 T cells in vitro and in vivo for memory and nonmemory antibacterial cytokine responses. Proceedings of the National Academy of Sciences, 100(10), 6009-6014.
  45. Bukowski, J. F., & Percival, S. S. (2008). L-theanine intervention enhances human γδ T lymphocyte function. Nutrition reviews, 66(2), 96-102.
  46. Li, C., Yan, Q., Tang, S., Xiao, W., & Tan, Z. (2018). Alteration of mevalonate pathway in rat splenic lymphocytes: possible role in cytokines secretion regulated by L-theanine. BioMed research international, 2018.
  47. Saeed, M., Yatao, X., Tiantian, Z., Qian, R., & Chao, S. (2019). 16S ribosomal RNA sequencing reveals a modulation of intestinal microbiome and immune response by dietary L-theanine supplementation. Poultry science, 98(2), 842-854.
  48. Chen, L., Xiao, W. J., Yan, Q. X., Gong, Z. H., Zhang, S., Zeng, L., … & Zhou, Y. H. (2020). Protective effects of l-theanine. Archives of Pharmacal Research, 1-42.
  49. Zarse, K., Jabin, S., & Ristow, M. (2012). L-Theanine extends lifespan of adult Caenorhabditis elegans. European journal of nutrition, 51(6), 765-768.
  50. Haskell, C. F., Kennedy, D. O., Milne, A. L., Wesnes, K. A., & Scholey, A. B. (2008). The effects of L-theanine, caffeine and their combination on cognition and mood. Biological psychology, 77(2), 113-122.
  51. Einöther, S. J., Martens, V. E., Rycroft, J. A., & De Bruin, E. A. (2010). L-theanine and caffeine improve task switching but not intersensory attention or subjective alertness. Appetite, 54(2), 406-409.
  52. Giesbrecht, T., Rycroft, J. A., Rowson, M. J., & De Bruin, E. A. (2010). The combination of L-theanine and caffeine improves cognitive performance and increases subjective alertness. Nutritional neuroscience, 13(6), 283-290.
  53. Owen, G. N., Parnell, H., De Bruin, E. A., & Rycroft, J. A. (2008). The combined effects of L-theanine and caffeine on cognitive performance and mood. Nutritional neuroscience, 11(4), 193-198.
  54. Kim, S., Jo, K., Hong, K. B., Han, S. H., & Suh, H. J. (2019). GABA and l-theanine mixture decreases sleep latency and improves NREM sleep. Pharmaceutical biology, 57(1), 64-72.
  55. Miyagawa, K., Hayashi, Y., Kurihara, S., & Maeda, A. (2008). Co‐administration of l‐cystine and l‐theanine enhances efficacy of influenza vaccination in elderly persons: Nutritional status‐dependent immunogenicity. Geriatrics & gerontology international, 8(4), 243-250.
  56. Kawada, S., Kobayashi, K., Ohtani, M., & Fukusaki, C. (2010). Cystine and theanine supplementation restores high-intensity resistance exercise-induced attenuation of natural killer cell activity in well-trained men. The Journal of Strength & Conditioning Research, 24(3), 846-851.
  57. Murakami, S., Kurihara, S., Koikawa, N., Nakamura, A., Aoki, K., Yosigi, H., … & Ohtani, M. (2009). Effects of oral supplementation with cystine and theanine on the immune function of athletes in endurance exercise: randomized, double-blind, placebo-controlled trial. Bioscience, biotechnology, and biochemistry, 73(4), 817-821.
  58. Murakami, S., Kurihara, S., Titchenal, C. A., & 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(1), 23.
  59. Kurihara, S., Shibahara, S., Arisaka, H., & Akiyama, Y. (2007). Enhancement of antigen-specific immunoglobulin G production in mice by co-administration of L-cystine and L-theanine. Journal of Veterinary Medical Science, 69(12), 1263-1270.
  60. Kurihara, S., Shibakusa, T., & Tanaka, K. A. (2013). Cystine and theanine: amino acids as oral immunomodulative nutrients. Springerplus, 2(1), 635.
  61. Kurihara, S., Hiraoka, T., Akutsu, M., Sukegawa, E., Bannai, M., & Shibahara, S. (2010). Effects of L-cystine and L-theanine supplementation on the common cold: a randomized, double-blind, and placebo-controlled trial. Journal of amino acids, 2010.
  62. Rowe, C. A., Nantz, M. P., Bukowski, J. F., & 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(5), 445-452.
  63. Matsumoto, K., Yamada, H., Takuma, N., Niino, H., & Sagesaka, Y. M. (2011). Effects of green tea catechins and theanine on preventing influenza infection among healthcare workers: a randomized controlled trial. BMC complementary and alternative medicine, 11(1), 1-7.
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