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How does theanine help you to relax?

Published Jan 11, 2021 | Updated Feb 8, 2024

If you are looking for a simple way to help you relax, you may be interested in a unique amino acid called L-theanine which is naturally found in tea leaves and some mushrooms. L-theanine constitutes 1-2% of the dry weight of green tea [1] and it has been shown to promote relaxation without sedation [2].

what is your stress response and how is it measured?

Researchers differentiate aspects of anxiety into state and trait anxiety. Trait anxiety is one’s general level of anxiety and it’s linked to your personality type. State anxiety is triggered by an acute stressor, such as public speaking or your first day at a new job. In these situations, the brain releases your stress-related hormone cortisol which in turn stimulates the release of adrenaline, and this is known as your “fight or flight response”. Adrenaline initiates a stress response by increasing heart rate and blood pressure [3] whilst reducing blood flow to non-essential functions such as the brain, stomach and sex organs.

how does l-theanine work?

It is suggested that L-theanine increases the relative concentration of GABA compared to the excitatory pathway, glutamate in the brain. GABA’s primary role is to aid relaxation without sedation and some studies suggest that it can further limit the stress response by reducing blood pressure, heart rate, and muscle contraction [4].

A clinical trial showed that 200mg of L-theanine significantly reduced subjective stress responses to multitasking cognitive stressors compared to placebo and saliva cortisol levels were also lowered 3 hours post-ingestion [5].

Clinical evidence has shown that L-theanine can amplify alpha brain waves which are associated with a state of relaxation and alertness, often referred to as a “wakeful relaxation” [6]. Another study showed that oral ingestion of 200mg L-theanine increased brain levels after 30 minutes and peaked at 5 hours [7]. Similar results of increased alpha waves were noted in those with high levels of trait anxiety, upon 200 mg L-theanine intake [13]. A review of 9 studies found that regular intake of 200-400 mg/day of L-theanine has a beneficial effect on stress and anxiety [14].

can I drink green tea or buy GABA supplements?

To obtain a therapeutic dose of L-theanine from tea you would need to consume up to 15 cups of tea [8]. Green tea can contain caffeine which can stimulate and cause laxative effects as well as certain antioxidants which may hinder iron absorption.

Brain feed’s L-theanine is naturally extracted from green tea and provides 250mg L-theanine which is equivalent to 15-20 cups of green tea. Additional 15% off your 1st order using code NEW15.

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L-theanine can freely enter the brain. GABA differs from L-theanine in its ability to cross the blood-brain barrier [9]. GABA supplements are non-approved in the UK whereas synthetic forms of L-theanine are common and natural, high strength variants can be bought in health food stores and online.

l theanine benefits l theanine side effects

The great news is research shows that some natural alternatives that encourage self-care and positive lifestyle changes may be linked to the production of GABA. Did you know that brief bouts of vigorous exercise can do wonders for the brain?

The Journal of Neuroscience published a study that showed doing an average of 11.5 minutes of vigorous exercise has shown to boost the production of GABA post-exercise [10]. If you fancy a less intense form of exercise, 60 minutes of yoga appears to be just as effective. A 12-week yoga intervention appeared to be more beneficial for increasing GABA production than walking for the same period. This exhibited additional benefits such as improved mood and decreased anxiety [11]. Mediating for 60 minutes also appears to increase the activity of a part of the brain which implicates the production GABA [12].


[1]Eschenauer et al. (2006). Pharmacology and therapeutic uses of theanine. American Journal of Health-System Pharmacy. [2]Bryan (2008) Psychological effects of dietary components of tea: caffeine and L-theanine. Nutrition Reviews.[3]Hannibal et al. (2014) Chronic Stress, Cortisol Dysfunction, and Pain: A Psychoneuroendocrine Rationale for Stress Management in Pain Rehabilitation. Physical Therapy.[4] Adhikary and Mandal (2017) l-theanine: A potential multifaceted natural bioactive amide as health supplement. Asian Pacific Journal of Tropical Biomedicine. [5] White et al. (2016) Anti-Stress, Behavioural and Magnetoencephalography Effects of an l-Theanine-Based Nutrient Drink: A Randomised, Double-Blind, Placebo-Controlled, Crossover Trial. Nutrients. [6] Bryan (2008) Psychological effects of dietary components of tea: caffeine and L-theanine: Nutrition Reviews. [7] Lu et al. (2004) The acute effects of L-theanine in comparison with alprazolam on anticipatory anxiety in humans. Human Psychopharmacology: Clinical and Experimental [8] Vuong, Q.V., Bowyer, M.C., Roach, P.D., 2011. L-Theanine: properties, synthesis and isolation from tea. Journal of the Science of Food and Agriculture 91, 1931–1939.[9] Tian et al. (2018) Homotaurine, a safe blood-brain barrier permeable GABAA-R-specific agonist, ameliorates disease in mouse models of multiple sclerosis. Sci Rep 8, 16555. [10] Maddock et al (2016) Acute Modulation of Cortical Glutamate and GABA Content by Physical Activity. Journal of Neuroscience. [11] Streeter et al. (2010) Effects of Yoga Versus Walking on Mood, Anxiety, and Brain GABA Levels: A Randomized Controlled MRS Study. The Journal of Alternative and Complementary Medicine [12] Guglietti et al (2013) Meditation-Related Increases in GABAB Modulated Cortical Inhibition. Brain Stimulation. [13] Hidese, S. et al. (2019). Effects of L-Theanine Administration on Stress-Related Symptoms and Cognitive Functions in Healthy Adults: A Randomized Controlled Trial. Nutrients, 11(10), p.2362. [14] Williams, al. (2019). The Effects of Green Tea Amino Acid L-Theanine Consumption on the Ability to Manage Stress and Anxiety Levels: a Systematic Review. Plant Foods for Human Nutrition.

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