Medically reviewed: June 7, 2018
What is L-Theanine?
Theanine is derived from tea leaves. Tea is native to eastern Asia and is a member of the Theaceae family. This evergreen shrub or tree grows to over 9 m in height and is pruned from 60 cm to 1.5 m for cultivation. Its dark green, serrated-edged leaves are alternate and oval, while its white and fragrant blossoms appear singly or in clusters.
The chemical has also been isolated from the edible mushroom Boletus badius. The mushroom is commonly found in late summer and autumn in the United States, and is reddish brown to dark brick/brown in color with a 4 to 12 cm tall stem. The flesh is white to yellow in color, and becomes a light blue/green color when cut or bruised.
Gamma-ethylamino-L-glutamic acid; derived from Boletus badius and Camellia sinensis
L-theanine is also known as Suntheanine.
What is it used for?
Second only to water, tea is the most widely consumed beverage in the world. L-theanine was discovered as a constituent of green tea in 1949 and was approved in Japan in 1964 for unlimited use in all foods, including chocolates, soft drinks, and herb teas, except infant foods. It also provides a unique umami (brothy or savory) taste and flavor to green tea infusion.
L-theanine may help relieve stress by inducing a relaxing effect without drowsiness and may also possess immunologic attributes. Theanine may also have effects on the cardiovascular system and play a preventative role in cancer; however, limited clinical information is available to support these claims.
What is the recommended dosage?
Data supporting a clinical role for theanine are weak. Studies reporting an anti-anxiety effect used single doses of theanine 200 to 250 mg.
None well established.
Information regarding safety and efficacy in pregnancy and lactation is lacking.
None well documented.
Few adverse reactions have been reported. Adverse reactions recorded in human studies using tea extracts include headache, dizziness, and GI symptoms.
Theanine is sold in the United States as a dietary supplement and has been granted GRAS (generally recognized as safe) status by the Food and Drug Administration.