CM Journal


Why Use L-Theanine in Your Practice?

Posted April 18, 2019

By: Dr. Colin O’Brien ND, Medical Director, Cyto-Matrix


Why Use L-Theanine in Your Practice?

Many practitioners have their ‘favourite’ nutrient or herbal treatment for patients who present with high stress levels, anxiety or difficulty falling asleep. Indeed, there are many great options that can positively address all three of these interconnected concerns. A few favourites include GABA, 5-HTP, inositol, lavender, and, of course, magnesium. Yet, in select cases, the amino acid L-theanine deserve to be considered.

For practitioners that are less familiar with the nutrient, L-theanine is a single amino acid, naturally found in green tea, that is well-known to calm the mind and improve focus. Research has found that L-theanine can increase levels of various neurotransmitters in the brain, such as serotonin, dopamine and GABA[i], while also blocking excitatory glutamate receptors.[ii] Ultimately, the actions of L-theanine lead to an increase in alpha-brain waves and create a calm, yet focused, state. [iii] Clinical trials have confirmed that, in individuals given supplemental L-theanine, these effects can reduce anxiety and improve stress markers such as heart rate, blood pressure and salivary immunoglobulin A.[iv] [v] [vi]

This information is important, from a clinical perspective, for a number of reasons. First of all, positively impacting multiple neurotransmitters, as opposed to targeting just one in particular (i.e.GABA or serotonin), has inherent advantages. Unless laboratory confirmation or other clear signs of a specific single neurotransmitter imbalance are present, a balanced approach is justified and sound. Arguably, this is also a gentler approach with a reduced likelihood of negative side-effects.

Secondly, although L-theanine can calm an overactive mind, it does so without jeopardizing alertness or causing sedation. In fact, the increase in alpha-brain wave activity helps to increase focus. Clinically, this means that L-theanine is a great option for stressed-out students that are studying for exams but still need to be cognitively sharp! Similarly, many practitioners will use L-theanine in children with attention deficit-hyperactivity disorder (ADHD) or for adults working in highly stressful and demanding environments.[vii]

Finally, L-theanine is a useful and practical clinical option for a broad range of patient profiles. L-theanine is an extremely safe option for daily use[viii]. Various research also shows that it positively affects alpha brain waves within just 30 minutes after ingestion.[ix] This means that L-theanine can be used acutely, preventatively, or on an ongoing basis to improve mood, cognition, sleep and stress-coping. Capsules can also be opened and mixed in water throughout the day or the powder can be dissolved under the tongue for quick-action. The evidence-based dosage ranges from 50-400mg per day and is highly variable depending on the clinical indications and individual circumstances.



[i] J Herb Pharmacother. 2006;6(2):21-30.

[ii] Biosci Biotechnol Biochem. 2002 Dec;66(12):2683-6.

[iii] Asia Pac J Clin Nutr. 2008;17 Suppl 1:167-8.

[iv] Hum Psychopharmacol. 2004 Oct;19(7):457-65.

[v] Biol Psychol. 2007 Jan;74(1):39-45.

[vi] J Physiol Anthropol. 2012 Oct 29;31:28.

[vii] Altern Med Rev. 2011 Dec;16(4):348-54

[viii] Food Chem Toxicol. 2006 Jul;44(7):1158-66

[ix] Asia Pac J Clin Nutr. 2008;17 Suppl 1:167-8.