L-theanine
Scientific Name(s):Gamma-ethylamino-L-glutamic acid 1
Common Name(s): L-theanine , Suntheanine 1
Clinical Overview
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Uses of L-theanine
L-theanine may help relieve stress by inducing a relaxing effect without drowsiness. It may also boost natural resistance to microbial infections and perhaps even tumors. Limited information is available to support these claims.
L-theanine Dosing
Based on the alpha-wave study, a dose of 50 to 200 mg may provide a relaxation effect. No dosage of L-theanine is suggested for enhanced immune system functioning; however, volunteers in a pilot study consumed approximately 600 mL of tea a day.
Contraindications
Avoid use in patients with known hypersensitivity reactions to L-theanine.
Pregnancy/Lactation
Information regarding safety and efficacy in pregnancy and lactation is lacking.
L-theanine Interactions
None well documented.
L-theanine Adverse Reactions
L-theanine is enzymatically synthesized by Taiyo Kagaku Co. Ltd., Japan and is extensively marketed in over 50 food products (eg, chocolate, soft drinks, herb teas) in Japan. Thus far, it has not resulted in any reported adverse reactions.
Toxicology
Tests fail to reveal any toxicities with L-theanine.
Botany
Black, oolong, and green tea are produced from the leaves of Camellia sinensis . C. sinensis 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. 2
History
Second only to water, tea is one of the most widely consumed beverages in the world. With the exception of a mushroom (eg, Xerocomus badius ) and certain species belonging to genus Camellia ( C. japonica and C. sasanqua ), L-theanine is a unique amino acid found only in the tea plant. L-theanine was approved in Japan in 1964 for unlimited use in all foods (including chocolates, soft drinks, herb teas), except infant foods. It also provides a unique umami (brothy or savory) taste and flavor to green tea infusion. 1 , 2 , 3 , 4 L-theanine has been used in cosmetics to moisturize the skin. 5
Chemistry
L-theanine was discovered in 1949 and constitutes 1% to 2% of the dry weight of tea leaves. It exists only in the free (nonprotein) form. Taiyo Kagaku Co. Ltd., Japan, has developed an enzymatic method to manufacture synthetic L-theanine ( Suntheanine ). 1 , 2 , 3
L-theanine Uses and Pharmacology
L-theanine's mechanism of action has not been fully elucidated.
Recent literature searches of peer-reviewed scientific studies are mostly associated with theanine. The results specifically associated with L-theanine are discussed below.
Relaxing effectAnimal data
Research reveals little or no information regarding the relaxing effects of this product.
Clinical dataL-theanine is able to cross the blood-brain barrier and most research has focused on its relaxing effect. Brain waves were measured in 50 high-anxiety and low-anxiety human volunteers after the oral administration of 50 to 200 mg of L-theanine. L-theanine promoted the generation of alpha-brain waves, an index of relaxation, and induced a relaxed but nondrowsy state in the volunteers. Emission intensity of the alpha-brain waves was determined to be dose-dependent. 1 , 6
Immune system functioningAnimal data
Research reveals little or no information regarding the immune system functioning of this product.
Clinical dataL-theanine may provide natural resistance to microbial infections and perhaps even tumors. In a recent pilot study, 11 healthy non-tea drinking volunteers were asked to consume approximately 600 mL/day of black tea for either 2 or 4 weeks. Another 10 healthy, non-tea and non-coffee-drinking volunteers were asked to drink 5 to 6 cups per day of instant coffee. The tea group consumed approximately 1.3 mmol/day of L-theanine. Cell samples from the volunteers on the tea regimen indicated that the brief exposure to the tea's L-theanine, which is metabolized to ethylamine in the liver, initiated immunologic memory. When bacteria were introduced to the ethylamine-exposed cells, these cells multiplied 10-fold, producing larger amounts of T-cells that fought the bacteria. Cells not exposed to tea did not attack the invading antigens. The first line of defense against many types of bacterial, viral, fungal, and parasitic infections is gamma-delta T-cells in the blood. The researchers of this study suggest further isolating and refining L-theanine from tea to use it as a drug to boost the infection defense of the body. 7
Dosage
Based on the alpha-wave study, a dose of 50 to 200 mg may provide a relaxation effect. No dosage of L-theanine is suggested for enhanced immune system functioning; however, volunteers in a pilot study consumed approximately 600 mL of tea a day.
Pregnancy/Lactation
Information regarding safety and efficacy in pregnancy and lactation is lacking.
Interactions
None well documented.
Adverse Reactions
L-theanine is enzymatically synthesized by Taiyo Kagaku Co. Ltd., Japan and is extensively marketed in over 50 food products (eg, chocolate, soft drinks, herb teas) in Japan. Thus far, it has not resulted in any reported adverse reactions.
Toxicology
Toxicology profile is based primarily on historical data from consumption of L-theanine in green tea by consumers. The LD 50 of L-theanine is 5 g/kg. Mutagenicity and acute and subacute toxicity tests have failed to show toxicity of the synthetic L-theanine product Suntheanine . 1
Bibliography
1. Juneja LR, Chu D-C, Okubo T, Nagato Y, Yokogoshi H. L-theanine-a unique amino acid of green tea and its relaxation effect in humans. Trends Food Sci Technol . 1999;10:199-204.2. Green tea. Altern Med Rev . 2000;5:372-375.
3. Anonymous. Suntheanine : Relaxing, health promoting amino acid found in tea. Taiyo International, Inc.
4. Bailey R. Relaxation and “De-stressing” the Japanese way. Nutraceuticals World . 1999:36-37.
5. Kobayashi K, Nagato Y, Aoi N, et al. Effects of L-theanine on the release of alpha-brain waves in human volunteers. Nippon Nogeikagaku Kaishi . 1998:72:153-157.
6. Kamath AB, Wang L, Das H, Li L, Reinhold VN, Bukowski JF. Antigens in tea-beverage prime human Vgamma 2Vdelta 2 T-cells in vitro and in vivo for memory and nonmemory antibacterial cytokine responses. Proc Natl Acad Sci USA . 2003;100:6009-6014.
7. Hayashi T, Nakagaki M, Konno G. L-theanine as a moisturizer, and cosmetics containing the moisturizer. Jpn Kokai Tokkyo Koho . 1997:5.
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