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L-theanine vs GABA: How to relax your brain quickly?

Published Jul 28, 2022 | Updated Feb 8, 2024

L-theanine is a popular calming nutrient. Are l-theanine and GABA, the main chemical that helps your brain take a break to relax, connected? Let’s take a look at the GABA vs l-theanine list to determine which supplement works best for you.

GABA is the main chemical that helps your brain take a break to relax. It has widespread importance with its network covering 44% of your brain[1]. It’s found in plants and animals. Your gut microbes produce GABA for its use to relax muscles, heart health, and the immune system[2]. Dietary sources include kimchi, fermented soybean, sourdough, fermented fish, and white tea[3,4], which provide small amounts of GABA. Holland and Barrett in the UK are yet to start selling it. Why is that? Well, if you live in the US, you can walk into a health store and buy GABA. UK, however, classifies it as medication and its sale as a food supplement is banned. 

GABA - what does it do?

If you are looking to get into a zen mode more often by consuming high amounts of GABA-rich foods or supplements, it would be advisable to look for alternative ways of how to increase GABA naturally. The brain has a protective layer of cells that control the entry of substances. This layer is called the blood-brain barrier and only a small amount of GABA can cross over[5].

What does l-theanine do?

L-theanine is a nutrient found in green tea and makes up 1-2% of the dry weight of tea leaves. A standard cup of tea may contain up to 10-20mg of l-theanine[6]. How to relax your brain with l-theanine? This natural compound helps to promote relaxation without making you drowsy. It increases alpha waves in the brain which is a state of deep relaxation while being alert, much like meditation[7]. 

Does l-theanine increase GABA?

Yes, it increases the relative concentration of GABA[8]. Researchers looked at 15 years’ worth of l-theanine supplementation studies and concluded that regular intake of 200-400mg l-theanine (equivalent to 13-26 cups of tea) for up to 2 weeks had a stress-reducing and calming effect[9]. Studies done among depressed patients with anxiety found a decrease in anxiety levels after l-theanine intake[10]. 

Is it better to take l-theanine or GABA? 

L-theanine wins the battle to cross the blood-brain barrier. Once consumed, it can easily cross the blood-brain barrier and its effects on the brain are noted within 30 minutes[11]. The evidence on whether GABA supplements can cross the blood-brain barrier is mixed. On one hand, early studies said no, and on the other, some newer research shows GABA may be able to enter the brain in very small amounts[12,13]. Most importantly, based on an article from 2018 the BBB permeability of GABA has yet to be studied in humans[12]! Although many consumers claim that they experience benefits from the use of GABA, it’s unclear whether these supplements provide benefits beyond a placebo effect[13]. More research and a bigger sample in studies are needed to determine the exact effects and the time it takes to note those effects[14]. 

L-theanine side effects

L-theanine is considered safe even at high doses (up to 1200 mg) because tea has been one of the most widely consumed beverages in the world for decades.

Getting the most from your rest & relaxation

L-theanine can cross into the brain to promote relaxation without drowsiness and improve GABA levels. It can either be consumed from tea or as a supplement. L-theanine supplements found on the market are not created equally. L-theanine is either cheaply produced synthetically or is extracted naturally from green tea which is an extensive and expensive process. brain feed’s 250 mg l-theanine is extracted from green tea from the mountainous region of Hunan Province in South Central China and each capsule contains l-theanine equivalent to 15-20 cups of green tea.

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Here's a quick summary to help you choose the right supplement for you: 

GABA vs L-theanine in the brain



What is it?

Chemical messenger 

Isolated nutrient 

Freely cross the blood-brain barrier?



Available as a supplement in the UK?




Aids relaxation by counteracting excitatory pathways

Promotes relaxation by producing alpha waves


[1] Petroff, O.A.C. (2002). Book Review: GABA and Glutamate in the Human Brain. The Neuroscientist, [online] 8(6), pp.562–573.

[2] Vargas, R. (2018). The GABAergic System: An Overv                                                                                                                                  iew of Physiology, Physiopathology and Therapeutics. International Journal of Clinical Pharmacology & Pharmacotherapy, 3(2). 

[3] Sahab, N.R.M. et al. (2020). γ-Aminobutyric acid found in fermented foods and beverages: current trends. Heliyon, 6(11), p.e05526.

[4] Zhao, M. et al. (2011). Determination and Comparison of γ-Aminobutyric Acid (GABA) Content in Pu-erh and Other Types of Chinese Tea. Journal of Agricultural and Food Chemistry, 59(8), pp.3641–3648.

[5] Boonstra, E. et al. (2015). Neurotransmitters as food supplements: the effects of GABA on brain and behavior. Frontiers in Psychology, [online] 6.

[6] Türközü, D. et al. (2017). L-theanine, unique amino acid of tea, and its metabolism, health effects, and safety. Critical reviews in food science and nutrition, [online] 57(8), pp.1681–1687.

[7] Mason, R. (2001). 200 mg of Zen: L-Theanine Boosts Alpha Waves, Promotes Alert Relaxation. Alternative and Complementary Therapies, 7(2), pp.91–95. 

[8] White, D. 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, [online] 8(1), p.53.

[9] Lopes Sakamoto, F. et al. (2019). Psychotropic effects of L-theanine and its clinical properties: From the management of anxiety and stress to a potential use in schizophrenia. Pharmacological Research, 147, p.104395.

[10] Hidese, S. et al. (2016). Effects of chronic l-theanine administration in patients with major depressive disorder: an open-label study. Acta Neuropsychiatrica, [online] 29(2), pp.72–79.

[11] Nobre, A. et al. (2008). L-theanine, a natural constituent in tea, and its effect on mental state. Asia Pac J Clin Nutr, [online] 17(S1), pp.167–168. Available at:

[12] McVean, A. (2018). Gaba Supplements: Glorious, Gimmicky or Just Garbage? McGill. Office for Science and Society.

[13] Boonstra, E., de Kleijn, R., Colzato, L. S., Alkemade, A., Forstmann, B. U., & Nieuwenhuis, S. (2015). Neurotransmitters as food supplements: the effects of GABA on brain and behavior. Frontiers in Psychology, 6, 1520. 

[14] Hepsomali, P., Groeger, J. A., Nishihira, J., & Scholey, A. (2020). Effects of Oral Gamma-Aminobutyric Acid (GABA) Administration on Stress and Sleep in Humans: A Systematic Review. Frontiers in Neuroscience, 14.

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