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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].






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.



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 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.




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



Clinically Studied

Pharmaceutical Grade Cognitive and Mind Enhancing Complex
Made in Switzerland


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  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.
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  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.
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  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.
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  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.
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  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.
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  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.