What are L-theanine’s main benefits?

    Last Updated: October 3, 2023

    The current evidence shows that supplementation with L-theanine may help reduce stress and anxiety in people experiencing acutely stressful situations.[1] Furthermore, L-theanine may also prevent the increase in blood pressure caused by stressful mental tasks.[2] Some small studies have also found that L-theanine might lower depression and anxiety scores in healthy people and in people with major depressive disorder.[3][4]

    Supplementation with L-theanine may also improve some aspects of cognitive function, including attention, executive function, and memory.[5][6][3][4] That said, L-theanine has been found to impair executive function and lower attentional control when people are in an emotionally aroused state[7] or are undertaking stressful mental tasks.[8]

    Further evidence suggests that supplementation with L-theanine might also enhance sleep quality[3][4] by promoting a more relaxed state in the brain.[9] However, it is important to note that this evidence is derived predominantly from studies of healthy people. There is currently insufficient evidence to make firm conclusions about whether theanine can improve stress, anxiety, depression, cognitive function, or sleep quality in people with chronic conditions.


    1. ^Williams JL, Everett JM, D'Cunha NM, Sergi D, Georgousopoulou EN, Keegan RJ, McKune AJ, Mellor DD, Anstice N, Naumovski NThe Effects of Green Tea Amino Acid L-Theanine Consumption on the Ability to Manage Stress and Anxiety Levels: a Systematic Review.Plant Foods Hum Nutr.(2020-Mar)
    2. ^Ai Yoto, Mao Motoki, Sato Murao, Hidehiko YokogoshiEffects of L-theanine or caffeine intake on changes in blood pressure under physical and psychological stressesJ Physiol Anthropol.(2012 Oct 29)
    3. ^Shinsuke Hidese, Shintaro Ogawa, Miho Ota, Ikki Ishida, Zenta Yasukawa, Makoto Ozeki, Hiroshi KunugiEffects of L-Theanine Administration on Stress-Related Symptoms and Cognitive Functions in Healthy Adults: A Randomized Controlled TrialNutrients.(2019 Oct 3)
    4. ^Shinsuke Hidese, Miho Ota, Chisato Wakabayashi, Takamasa Noda, Hayato Ozawa, Tsutomu Okubo, Hiroshi KunugiEffects of chronic l-theanine administration in patients with major depressive disorder: an open-label studyActa Neuropsychiatr.(2017 Apr)
    5. ^Dassanayake TL, Kahathuduwa CN, Weerasinghe VSL-theanine improves neurophysiological measures of attention in a dose-dependent manner: a double-blind, placebo-controlled, crossover study.Nutr Neurosci.(2022-Apr)
    6. ^Yoshitake Baba, Shun Inagaki, Sae Nakagawa, Toshiyuki Kaneko, Makoto Kobayashi, Takanobu TakiharaEffects of l-Theanine on Cognitive Function in Middle-Aged and Older Subjects: A Randomized Placebo-Controlled StudyJ Med Food.(2021 Apr)
    7. ^Grace E Giles, Caroline R Mahoney, Tad T Brunyé, Holly A Taylor, Robin B KanarekCaffeine and theanine exert opposite effects on attention under emotional arousalCan J Physiol Pharmacol.(2017 Jan)
    8. ^Crystal F Haskell, David O Kennedy, Anthea L Milne, Keith A Wesnes, Andrew B ScholeyThe effects of L-theanine, caffeine and their combination on cognition and moodBiol Psychol.(2008 Feb)
    9. ^Theertham P Rao, Motoko Ozeki, Lekh R JunejaIn Search of a Safe Natural Sleep AidJ Am Coll Nutr.(2015)