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Difference Between Theanine & L Theanine

By Mitch Jacobson ; Updated July 27, 2017

L-theanine is a non-protein forming, water-soluble amino acid commonly used to treat anxiety and high blood pressure. In both medical and commercial literature, "L-theanine" is often used interchangeably with "theanine," but there is a distinction.


Most amino acids exist in both an L- form and a D- form. These raw forms refer to the direction in which their chemical chains spiral. The L- form is the version usually considered safe for human consumption. L-theanine is found naturally in green tea and certain mushrooms. D-theanine does not occur naturally in foods.

The term theanine usually refers to the commercially available extraction of L-theanine, though laboratory studies have found both forms of the amino acid in consumer products labeled theanine.


A study published in "Biological Psychology" in January 2007 found L-theanine to be effective in treating conditions such as anxiety and high blood pressure. The National Institutes of Health (NIH) reports studies confirming the augmentation of certain cancer drugs such as doxorubicin. L-theanine also appears to relieve insomnia, prevent dementia and provide cardiovascular support, though more evidence is needed. There are currently no known contraindications for L-theanine.


There is little data to support recommended dosages for any of the conditions for which L-theanine is used. As with any drug or dietary supplement, an individual’s age, any current or pre-existing medical conditions and overall health should be considered before taking L-theanine. Consult with your physician about the suitability of the supplement in your case.


Though generally recognized as safe (GRAS) by the Food and Drug Administration, L-Theanine is not recommended for pregnant or lactating women. Because it lowers blood pressure, interactions may occur if it is combined with anti-hypertensive medications or stimulant medications.

Additionally, theanine supplements can contain extracts of both the L- and D- forms of the amino acid. Because D-theanine does not occur naturally in foods and has not been studied for its effects on human biology, seek the advice of a health care professional when choosing an L-theanine supplement.

Other Names

L-Theanine is also known as 5-N-ethyl-glutamine, gamma-ethylamino-L-glutamic acid, gamma-glutamylethylamide, N-ethyl-L-glutamine, theanine and suntheanine.

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