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Is Theanine Bad For You?

Also Known As: L-γ-glutamylethylamide



Short answer

L-Theanine, commonly known as theanine, is not harmful to the human body. Theanine has been ingested by humans for thousands of years by means of green and black teas, as well as some species of mushrooms. In more recent years, it has made its way into energy drinks such as Red Bull. Of all the ingredients found in energy drinks, theanine happens to one additive that poses no known acute or chronic risk to the human body.



Long answer

Without considering water, theanine is the most widely consumed beverage in the world.  It was found to be a derivative of green tea plants in 1949. It is a naturally occurring, non-essential amino acid present in the body.  It is responsible for providing the brain with the nourishment that it requires to experience decreased levels of stress.  Additionally, theanine is readily available in various black tea species and it can also be found in large quantities in green tea plants as well.  Aside from the direct interaction with stress levels in the brain, it also plays a vital role blood pressure control, human immune health, and proper sleep/wake cycles.   

Many people have used theanine as part of a vitamin and supplement regiment and have never complained of any adverse side effects.  However, there is a minority of theanine users that have experienced dizziness and headaches, when they reported having taken large doses.  Medical research subjects have experienced beneficial symptoms, such as “smooth and glowing skin”.  When the brain processes theanine, increased doses of the hormone dopamine are released.  This process is believed to have stopped a stroke in its onset, in some cases.  There is, however, no definitive scientific proof to confirm the claim.   

Doctors may recommend that those undergoing a treatment program with sedative drugs, opt for a diet low in theanine.  Since theanine is known to promote relaxation in the brain, taking it with sedatives may make the user feel additional sedation.  However, these findings are presented in general terms.  As with any other supplement use with caution and pregnant women should seek advice from their physician before using theanine.    

Possible short-term side effects

  • headaches
  • dizziness
  • gastrointestinal problems (rare)


  • stress reliever
  • blood pressure control
  • immune health
  • sleep/wake health

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Written by DeeAnne Oldham | 02-19-2016

Written by DeeAnne Oldham
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