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L-Theanine for Anxiety

author image Denton Dean
Denton Dean has written about current events and lifestyle issues since 2005. He is a former reporter for "Politicker," a "New York Observer" publication. Dean earned his Bachelor of Arts in political science from the University of Texas at Austin and his Master of Public Policy from the University of Chicago, where he studied health care policy.
L-Theanine for Anxiety
A woman is drinking green tea. Photo Credit: lofilolo/iStock/Getty Images

The amino acid L-theanine could have a positive effect on your anxiety and mood. Some research suggests L-theanine decreases anxiety and improves cognition, but its effect on anxiety is not yet fully understood. According to Memorial Sloan-Kettering Cancer Center, L-theanine appears to affect dopamine, serotonin and other neurotransmitters in rats, but no clinical trials have been conducted to conclusively determine its effect on humans.

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Green tea contains L-theanine, and tea drinkers often credit the beverage’s L-theanine content for inducing relaxed feelings and peace of mind. L-theanine is also sold as a nutritional supplement. Some energy drink manufacturers add the amino acid to their products as well.


L-theanine alters rats’ brain chemistry, but studies have drawn different conclusions about the implications of this research. A study published in Neurochemical Research found that L-theanine crossed the blood-brain barrier in rats. Their levels of norephinephrine, a stimulating neurotransmitter, did not increase, but their levels of serotonin, a neurotransmitter that regulates anxiety and depression, rose. Another study published the same year, however, found L-theanine decreased serotonin levels when administered to rodents.


A 2004 study published in Human Psychopharmacology found that administering 200 mg of L-theanine to human subjects made them feel more relaxed under “resting conditions.” The study only included 16 volunteers, far fewer than most large-scale, reputable clinical trials. In another study, UK researchers determined subjects were better able to perform mentally challenging problems when given a combination of L-theanine and caffeine rather than caffeine alone.


Some evidence shows that L-theanine may decrease anxiety by increasing alpha waves in the brain. Some researchers theorize these electromagnetic waves slow the mind. In one Netherlands study, participants given 50mg of L-theanine showed an increase in alpha waves as measured by an electroencephalograph (EEG). A very small Japanese study produced similar results.


The Food and Drug Administration classifies L-theanine supplements as "Generally Recognized as Safe" in dosages up to 250mg. Nevertheless, Sloan-Kettering suggests L-theanine could interact with sedatives, chemotherapy and cholesterol-lowering medications. If you take any of these drugs, check with your physician before consuming any L-theanine supplement.

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