As described above, theanine generally has calming or relaxing effects.[1][2][3][4] On the other hand, caffeine is a powerful central nervous system stimulant that is added to some energy drinks and naturally found in tea, coffee, and chocolate. Because tea contains both L-theanine and caffeine, some clinical studies have investigated the effects of theanine and caffeine individually and in combination. The current evidence shows that theanine might diminish some of the less desirable physiological effects of caffeine. For example, L-theanine has been shown to blunt both caffeine’s blood-pressure-increasing effects[5] and its sleep-disrupting effects.[6] However, theanine does not appear to blunt the beneficial effects of caffeine on cognitive performance. Instead, the above-described beneficial effects of theanine on some aspects of cognitive function,[7][8][3][4] such as attention, have been found to be enhanced when caffeine is simultaneously ingested.[9][10][11][12][13] That said, not all studies have found this synergistic effect.[14][5] Overall, dose-response studies of L-theanine and caffeine are currently lacking, and the existing studies are small; larger randomized controlled trials are needed to clarify the interaction between theanine and caffeine. Furthermore, the influence of theanine on the exercise-related performance-enhancing effect of caffeine is currently unclear.
References
- ^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)
- ^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)
- ^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)
- ^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)
- ^Peter J Rogers, Jessica E Smith, Susan V Heatherley, C W Pleydell-PearceTime for tea: mood, blood pressure and cognitive performance effects of caffeine and theanine administered alone and togetherPsychopharmacology (Berl).(2008 Jan)
- ^Baba Y, Takihara T, Okamura NTheanine maintains sleep quality in healthy young women by suppressing the increase in caffeine-induced wakefulness after sleep onset.Food Funct.(2023-Jul-31)
- ^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)
- ^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)
- ^Gail N Owen, Holly Parnell, Eveline A De Bruin, Jane A RycroftThe combined effects of L-theanine and caffeine on cognitive performance and moodNutr Neurosci.(2008 Aug)
- ^Kahathuduwa CN, Wakefield S, West BD, Blume J, Dassanayake TL, Weerasinghe VS, Mastergeorge AEffects of L-theanine-caffeine combination on sustained attention and inhibitory control among children with ADHD: a proof-of-concept neuroimaging RCT.Sci Rep.(2020-Aug-04)
- ^Chanaka N Kahathuduwa, Chathurika S Dhanasekara, Shao-Hua Chin, Tyler Davis, Vajira S Weerasinghe, Tharaka L Dassanayake, Martin Binksl-Theanine and caffeine improve target-specific attention to visual stimuli by decreasing mind wandering: a human functional magnetic resonance imaging studyNutr Res.(2018 Jan)
- ^Chanaka N Kahathuduwa, Tharaka L Dassanayake, A M Tissa Amarakoon, Vajira S WeerasingheAcute effects of theanine, caffeine and theanine-caffeine combination on attentionNutr Neurosci.(2017 Jul)
- ^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)
- ^F L Dodd, D O Kennedy, L M Riby, C F Haskell-RamsayA double-blind, placebo-controlled study evaluating the effects of caffeine and L-theanine both alone and in combination on cerebral blood flow, cognition and moodPsychopharmacology (Berl).(2015 Jul)