L-Theanine | L-γ-Glutamylethylamide | 5-N-Ethyl-Glutamine
L-theanine is a calming amino acid that naturally occurs in green tea. It is used as a nootropic because it supports focused attention, mental alertness, and a calm, relaxed sense of mental energy. L-theanine is often used with caffeine in nootropic stacks, because the combination supports task switching, accuracy, and focus. L-theanine promotes alpha brain waves (α-waves), which are thought of as a marker of relaxation. This brain state also reduces the perception of stress. L-theanine has a few other lesser known functional actions. L-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. And L-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 L-theanine are green and black tea (made from Camellia sinensis): L-theanine comprises up to 50% of total amino acids in tea leaves.
L-theanine is non-GMO, gluten-free, and vegan.
L-theanine has been studied clinically over a fairly wide range of doses, with the most common range being 100-400 mg. Evidence suggests a threshold response (see Neurohacker Dosing Principles) when L-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 L-theanine used in a Neurohacker formulation can vary significantly depending upon what other ingredients it’s combined with and the intent of the formulation. Neurohacker looks for additive or synergistic ingredient combinations. In some cases, ingredients tend to be most complimentary when used at certain ratios. L-theanine falls into this category. As an example, when used as part of a nootropic formula combined with a source of caffeine, L-theanine might be dosed to provide about double the dose of caffeine and/or theobromine (i.e., ~2:1 ratio). But 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 L-theanine in the brain increase within the first hour (i.e., it’s able to cross the blood-brain barrier, so in general, L-Theanine has fairly quick onset and is often experienced within 30-45 minutes of taking it.
Mood and Stress
 L.R. Juneja, D.-C. Chu, T. Okubo, Y. Nagato, H. Yokogoshi, Trends Food Sci. Technol. 10 (1999) 199–204.
 T. Terashima, J. Takido, H. Yokogoshi, Biosci. Biotechnol. Biochem. 63 (1999) 615–618.
 A. Higashiyama, H.H. Htay, M. Ozeki, L.R. Juneja, M.P. Kapoor, J. Funct. Foods 3 (2011) 171–178.
 S. Hidese, M. Ota, C. Wakabayashi, T. Noda, H. Ozawa, T. Okubo, H. Kunugi, Acta Neuropsychiatr. 29 (2017) 72–79.
 S.-K. Park, I.-C. Jung, W.K. Lee, Y.S. Lee, H.K. Park, H.J. Go, K. Kim, N.K. Lim, J.T. Hong, S.Y. Ly, S.S. Rho, J. Med. Food 14 (2011) 334–343.
 A. Takeda, K. Sakamoto, H. Tamano, K. Fukura, N. Inui, S.W. Suh, S.-J. Won, H. Yokogoshi, Cell. Mol. Neurobiol. 31 (2011) 1079–1088.
 T.I. Kim, Y.K. Lee, S.G. Park, I.S. Choi, J.O. Ban, H.K. Park, S.-Y. Nam, Y.W. Yun, S.B. Han, K.W. Oh, J.T. Hong, Free Radic. Biol. Med. 47 (2009) 1601–1610.
 K. Unno, K. Fujitani, N. Takamori, F. Takabayashi, K.-I. Maeda, H. Miyazaki, N. Tanida, K. Iguchi, K. Shimoi, M. Hoshino, Free Radic. Res. 45 (2011) 966–974.
 S. Hidese, S. Ogawa, M. Ota, I. Ishida, Z. Yasukawa, M. Ozeki, H. Kunugi, Nutrients 11 (2019).
 C.H. Song, J.H. Jung, J.S. Oh, K.S. Kim, Korean Journal of Nutrition 36 (2003) 918–923.
 M. Gomez-Ramirez, B.A. Higgins, J.A. Rycroft, G.N. Owen, J. Mahoney, M. Shpaner, J.J. Foxe, Clin. Neuropharmacol. 30 (2007) 25–38.
 A.C. Nobre, A. Rao, G.N. Owen, Asia Pac. J. Clin. Nutr. 17 Suppl 1 (2008) 167–168.
 D.J. White, S. de Klerk, W. Woods, S. Gondalia, C. Noonan, A.B. Scholey, Nutrients 8 (2016).
 S. Ogawa, M. Ota, J. Ogura, K. Kato, H. Kunugi, Psychopharmacology 235 (2018) 37–45.
 H. Yokogoshi, M. Kobayashi, M. Mochizuki, T. Terashima, Neurochem. Res. 23 (1998) 667–673.
 T. Yamada, T. Terashima, T. Okubo, L.R. Juneja, H. Yokogoshi, Nutr. Neurosci. 8 (2005) 219–226.
 T. Yamada, T. Terashima, S. Kawano, R. Furuno, T. Okubo, L.R. Juneja, H. Yokogoshi, Amino Acids 36 (2009) 21–27.
 J. Yao, X.-N. Shen, H. Shen, M. Wu, Zhonghua Yu Fang Yi Xue Za Zhi 46 (2012) 635–639.
 M. Shen, Y. Yang, Y. Wu, B. Zhang, H. Wu, L. Wang, H. Tang, J. Chen, Phytotherapy Research 33 (2019) 412–421.
 G. Zhu, S. Yang, Z. Xie, X. Wan, Neuropharmacology 138 (2018) 331–340.
 P.J. Nathan, K. Lu, M. Gray, C. Oliver, J. Herb. Pharmacother. 6 (2006) 21–30.
 H. Yokogoshi, M. Kobayashi, M. Mochizuki, T. Terashima, Neurochemical Research 23 (1998) 667–673.
 T. Kakuda, A. Nozawa, A. Sugimoto, H. Niino, Biosci. Biotechnol. Biochem. 66 (2002) 2683–2686.
 C. Wakabayashi, T. Numakawa, M. Ninomiya, S. Chiba, H. Kunugi, Psychopharmacology 219 (2012) 1099–1109.
 C. Miodownik, R. Maayan, Y. Ratner, V. Lerner, L. Pintov, M. Mar, A. Weizman, M.S. Ritsner, Clin. Neuropharmacol. 34 (2011) 155–160.
 X. Tian, L. Sun, L. Gou, X. Ling, Y. Feng, L. Wang, X. Yin, Y. Liu, Brain Res. 1503 (2013) 24–32.
 T. Sumathi, D. Asha, G. Nagarajan, A. Sreenivas, R. Nivedha, Environ. Toxicol. Pharmacol. 42 (2016) 99–117.
 M. Takeshima, I. Miyazaki, S. Murakami, T. Kita, M. Asanuma, J. Clin. Biochem. Nutr. 59 (2016) 93–99.
 K. Lu, M.A. Gray, C. Oliver, D.T. Liley, B.J. Harrison, C.F. Bartholomeusz, K.L. Phan, P.J. Nathan, Human Psychopharmacology: Clinical and Experimental 19 (2004) 457–465.
 M.S. Ritsner, C. Miodownik, Y. Ratner, T. Shleifer, M. Mar, L. Pintov, V. Lerner, J. Clin. Psychiatry 72 (2011) 34–42.
 K. Unno, N. Tanida, N. Ishii, H. Yamamoto, K. Iguchi, M. Hoshino, A. Takeda, H. Ozawa, T. Ohkubo, L.R. Juneja, H. Yamada, Pharmacol. Biochem. Behav. 111 (2013) 128–135.
 A. Yoto, M. Motoki, S. Murao, H. Yokogoshi, J. Physiol. Anthropol. 31 (2012) 28.
 K. Kimura, M. Ozeki, L.R. Juneja, H. Ohira, Biol. Psychol. 74 (2007) 39–45.
 H. Tamano, K. Fukura, M. Suzuki, K. Sakamoto, H. Yokogoshi, A. Takeda, Brain Res. Bull. 95 (2013) 1–6.
 M. Ozeki, L.R. Juneja, S. Shirakawa, J. Physiol. Anthropol. 23 (2004) 58.
 M.R. Lyon, M.P. Kapoor, L.R. Juneja, Altern. Med. Rev. 16 (2011) 348–354.
 H.-S. Jang, J.Y. Jung, I.-S. Jang, K.-H. Jang, S.-H. Kim, J.-H. Ha, K. Suk, M.-G. Lee, Pharmacology Biochemistry and Behavior 101 (2012) 217–221.
 S. Kurihara, T. Hiraoka, M. Akutsu, E. Sukegawa, M. Bannai, S. Shibahara, J. Amino Acids 2010 (2010) 307475.
 K. Matsumoto, H. Yamada, N. Takuma, H. Niino, Y.M. Sagesaka, BMC Complement. Altern. Med. 11 (2011) 15.
 C.A. Rowe, M.P. Nantz, J.F. Bukowski, S.S. Percival, Journal of the American College of Nutrition 26 (2007) 445–452.
 S. Kawada, K. Kobayashi, M. Ohtani, C. Fukusaki, J. Strength Cond. Res. 24 (2010) 846–851.
 A. Juszkiewicz, A. Glapa, P. Basta, E. Petriczko, K. Żołnowski, B. Machaliński, J. Trzeciak, K. Łuczkowska, A. Skarpańska-Stejnborn, J. Int. Soc. Sports Nutr. 16 (2019) 7.
 S. Murakami, S. Kurihara, C.A. Titchenal, M. Ohtani, J. Int. Soc. Sports Nutr. 7 (2010) 23.
 S. Murakami, S. Kurihara, N. Koikawa, A. Nakamura, K. Aoki, H. Yosigi, K. Sawaki, M. Ohtani, Biosci. Biotechnol. Biochem. 73 (2009) 817–821.
 M. Lei, J. Zuo, M. Li, Q. Gu, C. Hu, Chin. Med. J. 127 (2014) 1545–1549.
 N.H. Kim, H.J. Jeong, H.M. Kim, Amino Acids 42 (2012) 1609–1618.
 C. Li, H. Tong, Q. Yan, S. Tang, X. Han, W. Xiao, Z. Tan, Med. Sci. Monit. 22 (2016) 662–669.
 C. Li, Q. Yan, S. Tang, W. Xiao, Z. Tan, Biomed Res. Int. 2018 (2018) 1497097.
 A.B. Kamath, L. Wang, H. Das, L. Li, V.N. Reinhold, J.F. Bukowski, Proc. Natl. Acad. Sci. U. S. A. 100 (2003) 6009–6014.
 J.F. Bukowski, S.S. Percival, Nutr. Rev. 66 (2008) 96–102.
 S. Kurihara, S. Shibahara, H. Arisaka, Y. Akiyama, J. Vet. Med. Sci. 69 (2007) 1263–1270.
 T. Miyachi, T. Tsuchiya, A. Oyama, T. Tsuchiya, N. Abe, A. Sato, Y. Chiba, S. Kurihara, T. Shibakusa, T. Mikami, JPEN J. Parenter. Enteral Nutr. 37 (2013) 384–391.
 K. Miyagawa, Y. Hayashi, S. Kurihara, A. Maeda, Geriatr. Gerontol. Int. 8 (2008) 243–250.
 Y. Takagi, S. Kurihara, N. Higashi, S. Morikawa, T. Kase, A. Maeda, H. Arisaka, S. Shibahara, Y. Akiyama, J. Vet. Med. Sci. 72 (2010) 157–165.
 M. Saeed, X. Yatao, Z. Tiantian, R. Qian, S. Chao, Poult. Sci. 98 (2019) 842–854.
 Q. Yan, H. Tong, S. Tang, Z. Tan, X. Han, C. Zhou, Biomed Res. Int. 2017 (2017) 9747256.
 K. Zarse, S. Jabin, M. Ristow, Eur. J. Nutr. 51 (2012) 765–768.
 C.F. Haskell, D.O. Kennedy, A.L. Milne, K.A. Wesnes, A.B. Scholey, Biol. Psychol. 77 (2008) 113–122.
 S.J.L. Einöther, V.E.G. Martens, J.A. Rycroft, E.A. De Bruin, Appetite 54 (2010) 406–409.
 T. Giesbrecht, J.A. Rycroft, M.J. Rowson, E.A. De Bruin, Nutr. Neurosci. 13 (2010) 283–290.
 G.N. Owen, H. Parnell, E.A. De Bruin, J.A. Rycroft, Nutr. Neurosci. 11 (2008) 193–198.
 S. Kim, K. Jo, K.-B. Hong, S.H. Han, H.J. Suh, Pharm. Biol. 57 (2019) 65–73.
 S. Kurihara, T. Shibakusa, K.A. Tanaka, Springerplus 2 (2013) 635.