Effect of combined ingestion of L-theanine and L-arginine for short-term psychological stress in young adults: a randomized placebo-controlled study
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l-Theanine, the most abundant amino acid component in green tea, has anti-stress effects and refreshes the mental state. A recent study demonstrated that l-arginine, the second most abundant amino acid in green tea, might enhance the anti-stress effects of l-theanine. The aim of this study was to evaluated the effects of combined ingestion of l-theanine and l-arginine on psychological stress in humans. A randomized placebo-controlled trial was conducted including 120 healthy young adults (mean age 22.4 y, 63.3% female). Subjects were randomly assigned to theanine (200 mg l-theanine), combined theanine/arginine (200 mg l-theanine, 50 mg l-arginine), or placebo groups. After consuming a test beverage, we administered a stress-loading test (Uchida-Kraepelin performance test) and performed salivary alpha-amylase activity (sAA) measurements to assess the physiological stress response at 0 min (immediately after), 5 min, and 15 min. The changes in sAA at 15 min after the stress-loading test were -2.75 (11.2) kIU/L in the theanine/arginine group, -0.40 (11.5) kIU/L in the theanine group, and 6.95 (18.6) kIU/L in the placebo group. The values in the theanine/arginine (p=0.007) and theanine (p=0.02) groups differed significantly from those in the placebo group. However, the difference between theanine/arginine and theanine groups, was not statistically significant (p=0.74). From this study, no clear conclusion could be drawn regarding the potentiating effect of theanine and arginine combined ingestion on anti-stress effects in human.
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Overall, trials have indicated that supplementation with 200-400 mg/day of L-theanine can help to reduce both perceived and physiological markers of stress and anxiety in largely healthy adult samples, particularly during periods of acute stress.
“Overall, trials have indicated that supplementation with 200–400 mg/day of L-theanine can help to reduce both perceived and physiological markers of stress and anxiety in largely healthy adult samples, particularly during periods of acute stress.”
From Effects of L-theanine on cognition, mood and sleep: evidence from human trials (2026) · cites this paper as [34]
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Experimental — accuracy not yet measuredThis dosing range of L-theanine (200-400 mg/day) has been reported to be safe and well-tolerated.
“These studies have also reported this dosing range of L-theanine to be safe and well-tolerated.”
From Effects of L-theanine on cognition, mood and sleep: evidence from human trials (2026) · cites this paper as [34]
The Materials and Methods describe a single 200 mg dose of L-theanine, and the Results say all 120 participants completed the trial without dropout. That offers limited evidence of short-term tolerability at 200 mg, but the paper does not report that 200–400 mg/day is safe and well-tolerated or study daily dosing at 400 mg. (LLM, conf=0.78)
Experimental — accuracy not yet measuredA randomized trial in healthy young adults (n=120) reported statistically significant beneficial effects relative to placebo when L-theanine (200 mg) was administered alone or with L-arginine (50 mg) prior to an acute psychological stressor on subsequent salivary alpha-amylase activity.
“Another randomized trial conducted in healthy young adults (n = 120) has also reported statistically significant beneficial effects relative to placebo when L-theanine (200 mg) was administered either alone or in combination with L-arginine (50 mg) prior to an acute psychological stressor task on subsequent salivary alpha-amylase activity, a measure of physiological stress response (34).”
From Effects of L-theanine on cognition, mood and sleep: evidence from human trials (2026) · cites this paper as [34]
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Cites
State-Trait Anxiety Inventory for Adults
Spielberger, C. D. (2012) · PsycTESTS Dataset · doi:10.1037/t06496-000 · Cited by 3,479 · see citing works
Health Functions and Related Molecular Mechanisms of Tea Components: An Update Review
Tang, G., Meng, X., Gan, R., Zhao, C., Liu, Q., Feng, Y., Li, S., Wei, X., Atanasov, A. G., Corke, H., et al. (2019) · International Journal of Molecular Sciences · doi:10.3390/ijms20246196 · Cited by 423 · see citing works
Medicinal Benefits of Green Tea: Part I. Review of Noncancer Health Benefits
Cooper, R., Morré, D. J., & Morré, D. M. (2005) · The Journal of Alternative and Complementary Medicine · doi:10.1089/acm.2005.11.521 · Cited by 360 · see citing works
Enzymes of Arginine Metabolism
Morris, S. M. (2004) · Journal of Nutrition · doi:10.1093/jn/134.10.2743s · Cited by 357 · see citing works
l-theanine reduces psychological and physiological stress responses
Kimura, K., Ozeki, M., Juneja, L. R., & Ohira, H. (2007) · Biological Psychology · doi:10.1016/j.biopsycho.2006.06.006 · Cited by 349 · see citing works
Saeed, M., Naveed, M., Arif, M. A., Kakar, M. U., Manzoor, R., El-Hack, M. E. A., Alagawany, M. M., Tiwari, R., Khandia, R., Munjal, A. K., et al. (2017) · Biomedicine & Pharmacotherapy · doi:10.1016/j.biopha.2017.09.024 · Cited by 246 · see citing works
Yokogoshi, H., Kobayashi, M., Mochizuki, M., & Terashima, T. (1998) · Neurochemical Research · doi:10.1023/a:1022490806093 · Cited by 229 · see citing works
Yokogoshi, H., Kato, Y., Sagesaka, Y. M., Takihara-Matsuura, T., Kakuda, T., & Takeuchi, N. (1995) · Bioscience, Biotechnology, and Biochemistry · doi:10.1271/bbb.59.615 · Cited by 192 · see citing works
Wang, W., Zhang, L., Wang, S., et al. (2013) · Food Chemistry · doi:10.1016/j.foodchem.2013.10.117 · Cited by 130 · see citing works
TERASHIMA, T., TAKIDO, J., & YOKOGOSHI, H. (1999) · Bioscience, Biotechnology, and Biochemistry · doi:10.1271/bbb.63.615 · Cited by 112 · see citing works
Metabolism of Theanine, γ-Glutamylethylamide, in Rats
Unno, T., Suzuki, Y., Kakuda, T., Hayakawa, T., & Tsuge, H. (1999) · Journal of Agricultural and Food Chemistry · doi:10.1021/jf981113t · Cited by 109 · see citing works
Stress-reducing function of matcha green tea in animal experiments and clinical trials
Unno, K., Furushima, D., Hamamoto, S., Iguchi, K., Yamada, H., Morita, A., Horie, H., & Nakamura, Y. (2018) · Nutrients · doi:10.3390/nu10101468 · Cited by 85 · see citing works
Self-citationTheanine-induced reduction of brain serotonin concentration in rats
YOKOGOSHI, H., MOCHIZUKI, M., & SAITOH, K. (1998) · Bioscience, Biotechnology, and Biochemistry · doi:10.1271/bbb.62.816 · Cited by 83 · see citing works
Alagawany, M. M., El-Hack, M. E. A., Saeed, M., Naveed, M., Arain, M. A., Arif, M. A., Tiwari, R., Khandia, R., Khurana, S. K., Karthik, K., et al. (2019) · Journal of Animal Physiology and Animal Nutrition · doi:10.1111/jpn.13219 · Cited by 73 · see citing works
Unno, K., Fujitani, K., Takamori, N., Takabayashi, F., Maeda, K.-I., Miyazaki, H., Tanida, N., Iguchi, K., Shimoi, K., & Hoshino, M. (2011) · Free Radical Research · doi:10.3109/10715762.2011.566869 · Cited by 72 · see citing works
Self-citationUnno, K., Hara, A., Nakagawa, A., Iguchi, K., Ohshio, M., Morita, A., & Nakamura, Y. (2016) · Phytomedicine · doi:10.1016/j.phymed.2016.07.006 · Cited by 65 · see citing works
Self-citationUnno, K., Noda, S., Kawasaki, Y., Yamada, H., Morita, A., Iguchi, K., & Nakamura, Y. (2017) · Nutrients · doi:10.3390/nu9070777 · Cited by 65 · see citing works
Self-citationPharmacology and therapeutic uses of theanine
Eschenauer, G., & Sweet, B. V. (2006) · American Journal of Health-System Pharmacy · doi:10.2146/ajhp050148 · Cited by 61 · see citing works
Reduced baroreflex cardiac sensitivity predicts increased cognitive performance
Yasumasu, T., del Paso, G. A. R., Takahara, K., & Nakashima, Y. (2006) · Psychophysiology · doi:10.1111/j.1469-8986.2006.00377.x · Cited by 59 · see citing works
Sumathi, T., Shobana, C., Thangarajeswari, M., & Usha, R. (2015) · Drug and Chemical Toxicology · doi:10.3109/01480545.2014.900068 · Cited by 56 · see citing works
Li, C., Haiou, T., Yan, Q., Tang, S., Han, X., Xiao, W., & Tan, Z. (2016) · Medical Science Monitor · doi:10.12659/msm.897077 · Cited by 52 · see citing works
Unno, K., Furushima, D., Hamamoto, S., Iguchi, K., Yamada, H., Morita, A., Pervin, M., & Nakamura, Y. (2019) · Heliyon · doi:10.1016/j.heliyon.2019.e01653 · Cited by 43 · see citing works
Self-citationPervin, M., Unno, K., Konishi, T., & Nakamura, Y. (2021) · International Journal of Molecular Sciences · doi:10.3390/ijms22020508 · Cited by 41 · see citing works
Self-citationUnno, K., Noda, S., Kawasaki, Y., Yamada, H., Morita, A., Iguchi, K., & Nakamura, Y. (2017) · Journal of Clinical Biochemistry and Nutrition · doi:10.3164/jcbn.17-6 · Cited by 39 · see citing works
Self-citationYoneda, Y., Kuramoto, N., & Kawada, K. (2019) · Neurochemistry International · doi:10.1016/j.neuint.2019.104505 · Cited by 39 · see citing works
Tamano, H., Fukura, K., Suzuki, M., Sakamoto, K., Yokogoshi, H., & Takeda, A. (2013) · Brain Research Bulletin · doi:10.1016/j.brainresbull.2013.02.005 · Cited by 33 · see citing works
COMPARISON OF PEROXIDASE RESPONSE TO MENTAL ARITHMETIC STRESS IN SALIVA OF SMOKERS AND NON-SMOKERS
Goi, N., Hirai, Y., HARADA, H., Ikari, A., Ono, T., Kinae, N., Hiramatsu, M., Nakamura, K., & Takagi, K. (2007) · The Journal of Toxicological Sciences · doi:10.2131/jts.32.121 · Cited by 32 · see citing works
Intake of green tea inhibited increase of salivary chromogranin A after mental task stress loads
Yoto, A., Murao, S., Nakamura, Y., & Yokogoshi, H. (2014) · Journal of Physiological Anthropology · doi:10.1186/1880-6805-33-20 · Cited by 31 · see citing works
Nathan, P. J., Lu, K., Gray, M., & Oliver, C. (2006) · Journal of Herbal Pharmacotherapy · doi:10.1080/j157v06n02_02
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Payne, E. R., Aceves-Martins, M., Dubost, J., Greyling, A., & de Roos, B. (2025) · Nutrition Reviews · doi:10.1093/nutrit/nuaf054 · Cited by 14 · see citing works
Mátyus, R. O., Szikora, Z., Bodó, D., Vargáné Szabó, B., Csupor, É., Csupor, D., & Tóth, B. (2025) · Journal of Clinical Medicine · doi:10.3390/jcm14217710 · Cited by 5 · see citing works
Effects of L-theanine on cognition, mood and sleep: evidence from human trials
Cotter, J., & Kilpatrick, H. E. (2026) · Frontiers in Nutrition · doi:10.3389/fnut.2026.1922819
- Authors
- FURUSHIMA, D., SUGIYAMA, I., NOMURA, Y., UNNO, K., & YAMADA, H.
- Affiliations
- Kagoshima University (JP)
- Shizuoka University (JP)
- Venue
- Journal of Nutritional Science and Vitaminology
- Published
- 2022-12-31
- Volume
- 68
- Issue
- 6
- Pages
- 540-546
- ISSN
- 0301-4800 (ISSN-L)
- 1881-7742
- OpenAlex
- W4313391692
- Cited by
- 4
- References
- 29
- Citations by year
- 2026: 2 · 2025: 2
- FWCI
- 0.34
- Type
- journal article
- Language
- en
- Open access
- diamond
- doi.org
- Locations
- Journal of Nutritional Science and Vitaminology (publishedVersion)
- PubMed (publishedVersion)
- Topics
- Health Sciences › Medicine › Pathology and Forensic Medicine › Tea Polyphenols and Effects
- Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Medicinal Plants and Bioactive Compounds
- Health Sciences › Medicine › Complementary and alternative medicine › Medicinal Plant Extracts Effects
- Keywords
- theanine, L-arginine, psychological stress, salivary amylase, stress response, young adults
- MeSH terms
- Adult, Amino Acids, Arginine, Eating, Female, Glutamates, Humans, Male, Stress, Psychological, Tea, Young Adult
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