Should we drop the caffeine in favor of the tea? L-theanine promises ‘alert relaxation’ can it deliver performance gains or anything else like caffeine? And the first in a series of interviews with experts on disinformation in science and sport

Table of Contents

• L-theanine: alert relaxation from your cuppa?

• Jonathan Jarry-a disinformation warrior

• Episode takeaways:

  • References used for the MMB

L-theanine: alert relaxation from your cuppa?

L-theanine, an amino acid naturally found in green tea, has gained attention for its potential cognitive and relaxation benefits. Research suggests it promotes a state of calm alertness by increasing alpha brain wave activity and modulating neurotransmitters such as GABA, serotonin, and dopamine. Unlike sedatives, it does not cause drowsiness, making it appealing for reducing stress and anxiety while supporting focus and attention. L-theanine appears to enhance cognitive performance and reduce the jitteriness often associated with caffeine alone. Preliminary evidence also indicates possible benefits for sleep quality, cardiovascular health, and immune function, though more rigorous studies are needed to confirm these effects. Overall, L-theanine is considered safe, well-tolerated, and a promising supplement for promoting relaxation without impairing mental clarity. As to whether or not this substance has any benefits on athletic performance, we were hard pressed to turn up much in the medical literature. We did find some preliminary studies but nothing to make us believe that drinking your tea will make you any more successful as an athlete.

Jonathan Jarry-a disinformation warrior

About Jonathan according to Jonathan: Jonathan Jarry is a science communicator with McGill University’s Office for Science and Society (OSS), dedicated to separating sense from nonsense on the scientific stage. He has a Master’s degree in molecular biology and he brings his experience in cancer research, human genetics, rehabilitation research, and forensic biology to the work he does for the public. For ten years, he was also the co-creator and co-host of the award-winning podcast, The Body of Evidence. He is a guest lecturer in multiple university courses, including classes in science communication, and gives talks to both general and professional audiences. He is regularly interviewed in both English- and French-language media, such as The New York Times, CBC, and La Presse.

Imagine for a moment a world where a doctor consults a psychic medium for medical advice. No, this isn’t the latest dystopian novel; it’s the bizarre reality that Jonathan Jarry exposes in this episode. Dr. Joseph Mercola, who is apparently living in some alternative universe, has built an empire on health misinformation, all while consulting a medium who claims to channel a spirit named Balon. In this episode, we unpack the absurdity of Mercola’s wellness empire, where facts take a backseat to flashy marketing and pseudo-science. Jarry discusses the recent Mercola tapes, which reveal the extent of this madness and the dangerous influence it has on public health. We delve into the psychology of belief and why people are drawn to such nonsense, often overlooking the mountains of scientific evidence that contradicts the claims made by their favorite influencers. It’s a captivating discussion that not only highlights the dangers of disinformation but also explores the underlying psychological factors that make us susceptible to believing in the unbelievable. So, if you’ve ever wondered how someone can sell such outrageous claims with a straight face, tune in and prepare to have your perception of wellness influencers turned upside down.

Watch The Mercola Tapes on YouTube

Episode takeaways:

• L-theanine is a safe and inexpensive supplement that likely offers cognitive benefits but nothing for performance

• As technology and science grow increasingly complex, our craving for simple answers goes through the roof, because who doesn't love a nice black-and-white view of life?

• Dr. Mercola, a so-called wellness guru, has turned his alternative remedies into a cash cow, making millions selling nonsense that often contradicts established medical science.

• In the wild world of health misinformation, influencers like Mercola capitalize on our desire for easy solutions to complex health problems, while simultaneously twisting facts to fit their narrative.

References used for the MMB

• L-theanine is known in pop culture as a supplement that enhances cognitive performance while having sedative and mood relaxing effects - the science is generally favorable but limited (Dashwood & Visoli, 2025). 

• L-theanine is derived from tea leaves. Green/black/oolong teas can have “5.8 to 32 mg per 200 ml of brewed tea (3 g of dried tea leaves)” (Borzellca et al., 2006) - but there is no quality control for L-theanine dosage in leaves, so there’s no guarantee that any cup of tea has a measurable amount of L-theanine. 

• Non-protein amino acid with structural similarities to neurotransmitters glutamate and GABA. In the brain, has been identified as a competitive inhibitor of cannabinoid receptor 1 (CB1) (Liu et al., 2021). With low affinity, L-theanine also binds glutamate receptors (kainate and AMPA) (Kakuda et al., 2002).  L-theanine is a partial agonist of NMDA receptors (Sebih et al., 2021). L-theanine treatment in mice has been found to upregulate GABAergic and serotonergic receptor expression as well as increase dopamine, serotonin, and melatonin levels (Dasdellen et al., 2022)

• Very limited evidence for L-theanine increasing lifespan. One study in C. elegans (Zarse et al., 2012) showed a non-dose-dependent increase in average and maximum lifespan given L-theanine treatment. This has not been replicated in any human subjects study.

• L-theanine promotes “alert relaxation” (Lu et al., 2004, Nobre et al., 2008). 

• L-theanine promotes sleep quality (Kimura & Nirata, 1971, Rao et al., 2015), decreases sleep latency (Kim et al., 2019) in mice and human studies.

• Studies on L-theanine and exercise

  • L-theanine treatment in a double-blind, randomized controlled crossover study of elite curling athletes (n=22) resulted in an increase in shooting score and cognitive performance measured via a Stroop test (Yilmaz et al., 2013). Dosage: 6 mg/kg

  • L-theanine treatment in a double-blind, randomized control study of elite rowers (n=20) resulted in changes in exercise-dependent trajectories of immune system markers (IL-2, IL-4, IL-10, and IFN-y) (Zaragoza et al., 2019). Dosage: 150 mg

• L-theanine treatment in a double-blind, randomized control study of current and former college athletes (n=20) resulted in changes in movement accuracy during Makoto performance testing but did not change subjective reports of performance test experience or physical performance (Juszkiewicz et al., 2019). Dosage: 150 mg

Citations

• Borzelleca, J. F., Peters, D., & Hall, W. (2006). A 13-week dietary toxicity and toxicokinetic study with l-theanine in rats. Food and chemical toxicology : an international journal published for the British Industrial Biological Research Association, 44(7), 1158–1166. https://doi.org/10.1016/j.fct.2006.03.014

• Dasdelen, M. F., Er, S., Kaplan, B., Celik, S., Beker, M. C., Orhan, C., Tuzcu, M., Sahin, N., Mamedova, H., Sylla, S., Komorowski, J., Ojalvo, S. P., Sahin, K., & Kilic, E. (2022). A Novel Theanine Complex, Mg-L-Theanine Improves Sleep Quality via Regulating Brain Electrochemical Activity. Frontiers in nutrition, 9, 874254. https://doi.org/10.3389/fnut.2022.874254

• Dashwood, R., & Visioli, F. (2025). l-theanine: From tea leaf to trending supplement - does the science match the hype for brain health and relaxation?. Nutrition research (New York, N.Y.), 134, 39–48. https://doi.org/10.1016/j.nutres.2024.12.008

• Juszkiewicz, A., Glapa, A., Basta, P., Petriczko, E., Żołnowski, K., Machaliński, B., Trzeciak, J., Łuczkowska, K., & 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. https://doi.org/10.1186/s12970-019-0274-y

• Kakuda, T., Nozawa, A., Sugimoto, A., & Niino, H. (2002). Inhibition by theanine of binding of [3H]AMPA, [3H]kainate, and [3H]MDL 105,519 to glutamate receptors. Bioscience, biotechnology, and biochemistry, 66(12), 2683–2686. https://doi.org/10.1271/bbb.66.2683

• 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), 65–73. https://doi.org/10.1080/13880209.2018.1557698

• Kimura, R., & Murata, T. (1971). Influence of alkylamides of glutamic acid and related compounds on the central nervous system. I. Central depressant effect of theanine. Chemical & pharmaceutical bulletin, 19(6), 1257–1261. https://doi.org/10.1248/cpb.19.1257

• Liu, A., Lin, L., Xu, W., Gong, Z., Liu, Z., & Xiao, W. (2021). L-Theanine regulates glutamine metabolism and immune function by binding to cannabinoid receptor 1. Food & function, 12(13), 5755–5769. https://doi.org/10.1039/d1fo00505g

• Lu, K., Gray, M. A., Oliver, C., Liley, D. T., Harrison, B. J., Bartholomeusz, C. F., Phan, K. L., & Nathan, P. J. (2004). The acute effects of L-theanine in comparison with alprazolam on anticipatory anxiety in humans. Human psychopharmacology, 19(7), 457–465. https://doi.org/10.1002/hup.611

• Nobre, A. C., Rao, A., & Owen, G. N. (2008). L-theanine, a natural constituent in tea, and its effect on mental state. Asia Pacific journal of clinical nutrition, 17 Suppl 1, 167–168.

• Rao, T. P., Ozeki, M., & Juneja, L. R. (2015). In Search of a Safe Natural Sleep Aid. Journal of the American College of Nutrition, 34(5), 436–447. https://doi.org/10.1080/07315724.2014.926153

• Sebih, F., Rousset, M., Bellahouel, S., Rolland, M., de Jesus Ferreira, M. C., Guiramand, J., Cohen-Solal, C., Barbanel, G., Cens, T., Abouazza, M., Tassou, A., Gratuze, M., Meusnier, C., Charnet, P., Vignes, M., & Rolland, V. (2017). Characterization of l-Theanine Excitatory Actions on Hippocampal Neurons: Toward the Generation of Novel N-Methyl-d-aspartate Receptor Modulators Based on Its Backbone. ACS chemical neuroscience, 8(8), 1724–1734. https://doi.org/10.1021/acschemneuro.7b00036

• Yilmaz, U., Buzdagli, Y., Polat, M. L., Bakir, Y., Ozhanci, B., Alkazan, S., & Ucar, H. (2023). Effect of single or combined caffeine and L-Theanine supplementation on shooting and cognitive performance in elite curling athletes: a double-blind, placebo-controlled study. Journal of the International Society of Sports Nutrition, 20(1), 2267536. https://doi.org/10.1080/15502783.2023.2267536

• Zaragoza, J., Tinsley, G., Urbina, S., Villa, K., Santos, E., Juaneza, A., Tinnin, M., Davidson, C., Mitmesser, S., Zhang, Z., & Taylor, L. (2019). Effects of acute caffeine, theanine and tyrosine supplementation on mental and physical performance in athletes. Journal of the International Society of Sports Nutrition, 16(1), 56. https://doi.org/10.1186/s12970-019-0326-3

• Zarse, K., Jabin, S., & Ristow, M. (2012). L-Theanine extends lifespan of adult Caenorhabditis elegans. European journal of nutrition, 51(6), 765–768. https://doi.org/10.1007/s00394-012-0341-5Not a subscriber to the podcast? Click here!

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