L-Theanine is a very popular amino acid that is found naturally in tea, many types of mushrooms, and in a number of other foods.  It was first discovered in tea in 1949 and has been extensively researched ever since.  L-Theanine is sold as a dietary supplement in the United States.  The Food and Drug Administration (FDA) has given L-Theanine the classification GRAS (generally regarded as safe)[1].

This supplement is widely used for its ability to reduce anxiety without producing much sedation.  In fact, L-Theanine has been reported to be mildly stimulating.  Taking L-Theanine with caffeine has been shown in several clinical studies to  increase its effects[2][3].



What are some of the benefits of L-Theanine?

  • ⇒ Reduced Stress
  • ⇒ Improved Mood
  • ⇒ Decreased Anxiety
  • ⇒ Improvement in Cognitive Performance
  • ⇒ Increased Focus

How does it work?L-Theanine-link

Unlike the racetams, L-Theanine has very little influence on the ionotropic glutamate receptors.  It’s psychotropic effects are caused in part to its ability to increase dopamine levels in the brain[4].  Dopamine is the “feel good” neurotransmitter in the brain that plays a large role in pleasure, motivation, goal-oriented behavior, mood, and other important functions.  L-Theanine may also affect serotonin levels in the brain, but more research is necessary to confirm this[5].

Safety/Side Effects

L-Theanine is widely considered to be safe.  It is found naturally in many different types of teas, mushrooms, and other foods.  The FDA has classified L-Theanine as generally regarded as safe (GRAS)[1].  However, as with all supplements, you should always consult a physician before starting anything new.


The recommended dosage of L-Theanine is 150-250mg.  As with all supplements, you should always start at the low end to asses tolerance and work your way up as necessary.  Many people find that L-Theanine works much better when it is consumed with 100-200mg of caffeine.


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[1]  “FDA confirms GRAS status of Suntheanine”. NutraIngredients-USA.com. March 22, 2007.

[2]  Giesbrecht, T.; Rycroft, J.A.; Rowson, M.J.; De Bruin, E.A. (2010). “The combination of L-theanine and caffeine improves cognitive performance and increases subjective alertness”. Nutritional Neuroscience 13 (6): 283–90.

[3]  Owen, Gail N.; Parnell, Holly; De Bruin, Eveline A.; Rycroft, Jane A. (2008). “The combined effects of L-theanine and caffeine on cognitive performance and mood”.Nutritional Neuroscience 11 (4): 193–8

[4]  Nathan, Pradeep; Lu, Kristy; Gray, M.; Oliver, C. (2006). “The Neuropharmacology of L-Theanine(N-Ethyl-L-Glutamine)”. Journal of Herbal Pharmacotherapy 6 (2): 21–30.

[5]  Yokogoshi, Hidehiko; Mochizuki, Mikiko; Saitoh, Kotomi (1998). “Theanine-induced Reduction of Brain Serotonin Concentration in Rats”. Bioscience, Biotechnology, and Biochemistry 62 (4): 816–7