L-theanine; what is it and how does it help your brain?
By Laurentia Campbell, biomedical scientist, neuroscientist and nutritionist writer.
L-theanine has hit the headlines recently with new research emerging which shows potential brain-boosting, stress-protective effects. It has been added as a result to many adaptogenic (substances which may improve your resilience to stress) and nootropic (meant to improve cognitive performance and brain health) commercial supplements and products from matcha to CBD drinks and oils. But what is L-theanine and how does it work?
How does L-theanine affect the brain?
L-theanine is an amino acid which is found naturally in some non-starchy vegetables such as mushrooms, matcha and many plant sources. Recent research by Kimura et al (1) and Dietz et al (2) showed promise for L-theanine use for improved stress response and cognitive performance.
Our ability to think is regulated by brain neurotransmitters. These are chemicals which go between brain cells (neurones) and help transmit signals between receptors in our sensory organs (which detect changes in our environment and help us maintain a constant internal balance) to our central nervous system (our brain and spinal cord). The main excitatory neurotransmitter (which stimulates us to action) is Glutamate. It is essential for memory, learning, mood and problem-solving, as well as our ability to defend against threats (our flight or fight stress response). It stimulates our heart rate to increase, our blood sugar to rise and our gastric motility to slow (as our body focuses on running away from a threat which our prehistoric brains still see as a sabre tooth tiger predator) and gives the symptoms of brain hyper-stimulation or short-term stress. Glutamate is opposed by GABA (Gamma-aminobutyric acid), the main inhibitory neurotransmitter, which does the opposite to Glutamate and shuts down the brain, giving a calming, focused effect.
L-theanine competes with Glutamate for brain receptor sites and is easily able to cross the blood-brain barrier (as it is a neurotransmitter). This means it blocks the activity of Glutamate and enhances the effects of GABA, and therefore has a calming effect. It is thought to be responsible for the calming effects of plants such as CBD from the cannabis plant, and mushrooms and the focus that comes from plants such as green tea, jasmine tea, matcha and black tea such as Earl Grey tea. It is also thought to impact brain Dopamine (our pleasure brain chemical) levels, something imbalanced by too much use of technology, over and under exercise, over and under brain stimulation, stress and fatigue. Research by Nobre et al (3) found that L-Theanine also increased alpha brainwave activity which promotes relaxation. Reduced alpha wave activity has also been shown to improve the symptoms of ADHD (5).
Therefore it is said to promote a focused, reduced anxiety, calming, problem-solving and creativity-increasing state and to help reduce insomnia caused by stress (emotional from regret, grief, worry, work, relationships or physical as a result of imbalanced blood sugar, inflammation or chronic pain etc) or hyperactivity.
Where do I get L-theanine from?
L-theanine is sold in many supplements and products worldwide. However, it is unclear about the efficacy of these products. CBD drinks such as Trip Drinks contain L-theanine. They are said to help reduce anxiety and promote “wakeful relaxation” or “sedative effects without sleep” which is why it can help with turning your brain off and calming those hyperactive other-thinking thoughts that cause anxiety and sleeplessness.
L-theanine products have been found to improve brain relaxation. Studies suggest that the best dosage of L-theanine is 100–200mg and that its bioavailability is highest in its natural form (from plant sources such as matcha, green tea, CBD and so on rather than from synthetic sources). If you do purchase a L-theanine product, be sure to purchase one in the correct dosage and from a natural source. Also, it is best to have it as L-theanine not D-theanine which is less effective for calming and attention-promoting, problem-solving, and stress-buffering effects.
References
- 1. Kimura K, Ozeki M, Juneja LR, Ohira H. L-Theanine reduces psychological and physiological stress responses. Biol Psychol. 2007;74(1):39–45.
- Dietz C, Dekker M, Piqueras-Fiszman B. An intervention study on the effect of matcha tea, in drink and snack bar formats, on mood and cognitive performance. Food Res Int. 2017;99(Pt 1):72–83.
- Nobre AC, Rao A, Owen GN. L-theanine, a natural constituent in tea, and its effect on mental state. Asia Pac J Clin Nutr. 2008;17 Suppl 1:167–8.
- Walker M. Why we sleep: Unlocking the power of sleep and dreams: Simon and Schuster; 2017.
- Barrett JR, Tracy DK, Giaroli G. To sleep or not to sleep: a systematic review of the literature of pharmacological treatments of insomnia in children and adolescents with attention-deficit/hyperactivity disorder. J Child Adolesc Psychopharmacol. 2013;23(10):640–7.
