Will L-theanine Fix Your Bad Mood?

The market for supplements, such as L-theanine, believed to enhance mood naturally, is booming, but do they really work? The recent news about mental health in the United States, such as the data found in The State of Mental Health report for 2021 (Mental Health America), is striking.

Today we will look at L-theanine, an amino acid said to ease anxiety, stress, and insomnia. L-theanine is found in tea (black and green) and some varieties of mushrooms. The proposed actions of L-theanine are based on its chemical structure, which is very similar to that of glutamate, a naturally occurring amino acid involved in nerve transmission in the brain.

This handout covers some of the major research findings indicating a link between L-theanine consumption, mood, and cognition.

L-theanine Resources

Everett JM, Gunathilake D, Dufficy L, et al. Theanine consumption, stress and anxiety in human clinical trials: A systematic review. Journal of Nutrition & Intermediary Metabolism. 2016;4:41-42.

Foxe JJ, Morie KP, Laud PJ, Rowson MJ, de Bruin EA, Kelly SP. Assessing the effects of caffeine and theanine on the maintenance of vigilance during a sustained attention task. Neuropharmacology. 2012 Jun;62(7):2320-7. doi: 10.1016/j.neuropharm.2012.01.020. Epub 2012 Feb 2. PMID: 22326943.

Giesbrecht T, Rycroft JA, Rowson MJ, De Bruin EA. The combination of L-theanine and caffeine improves cognitive performance and increases subjective alertness. Nutr Neurosci. 2010 Dec;13(6):283-90. doi: 10.1179/147683010X12611460764840. PMID: 21040626.

Hidese S, Ota M, Wakabayashi C, Noda T, Ozawa H, Okubo T, Kunugi H. Effects of chronic l-theanine administration in patients with major depressive disorder: an open-label study. Acta Neuropsychiatr. 2017 Apr;29(2):72-79. doi: 10.1017/neu.2016.33. Epub 2016 Jul 11. PMID: 27396868.

Kakuda T. Neuroprotective effects of theanine and its preventive effects on cognitive dysfunction. Pharmacol Res. 2011 Aug;64(2):162-8. doi: 10.1016/j.phrs.2011.03.010. Epub 2011 Apr 6. PMID: 21477654.

Kimura K, Ozeki M, Juneja LR, Ohira H. L-Theanine reduces psychological and physiological stress responses. Biol Psychol. 2007 Jan;74(1):39-45. doi: 10.1016/j.biopsycho.2006.06.006. Epub 2006 Aug 22. PMID: 16930802.

Sarris J, Byrne GJ, Cribb L, Oliver G, Murphy J, Macdonald P, Nazareth S, Karamacoska D, Galea S, Short A, Ee C, Birling Y, Menon R, Ng CH. L-theanine in the adjunctive treatment of generalized anxiety disorder: A double-blind, randomised, placebo-controlled trial. J Psychiatr Res. 2019 Mar;110:31-37. doi: 10.1016/j.jpsychires.2018.12.014. Epub 2018 Dec 8. PMID: 30580081.

White DJ, de Klerk S, Woods W, Gondalia S, Noonan C, Scholey AB. Anti-stress, behavioural and magnetoencephalography effects of an L-theanine-based nutrient drink: A randomised, double-blind, placebo-controlled, crossover trial. Nutrients. 2016 Jan 19;8(1):53. doi: 10.3390/nu8010053. PMID: 26797633; PMCID: PMC4728665.

Yan J, Di X, Liu C, Zhang H, Huang X, Zhang J, Zhao Y, Zhang L, Chang Y, Liang Y, Tao R, Zhao B. The cessation and detoxification effect of tea filters on cigarette smoke. Sci China Life Sci. 2010 May;53(5):533-41. doi: 10.1007/s11427-010-0097-1. Epub 2010 May 23. PMID: 20596936.

Yoto A, Motoki M, Murao S, Yokogoshi H. Effects of L-theanine or caffeine intake on changes in blood pressure under physical and psychological stresses. J Physiol Anthropol. 2012 Oct 29;31(1):28. doi: 10.1186/1880-6805-31-28. PMID: 23107346; PMCID: PMC3518171.