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Theanine (L-theanine)

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Also listed as: L-theanine, 5-N-ethylglutamine
Related terms
Background
Evidencetable
Tradition
Dosing
Safety
Interactions
Attribution
Bibliography

Related Terms
  • 2-Amino-4-(ethylcarbamoyl)butyric acid, 2,4-dinitrophenyltheanine derivative (DNP-theanine), 5-N-ethylglutamine, amino acid theanine (5-N-ethylglutamine), black tea (Camellia sinensis), D/L-theanine, D-theanine, epitheaflavic acids, gamma-glutamylethylamide, green tea (Camellia sinensis), L-N-ethylglutamine, L-theanine, oolong tea, Suntheanine®, theaflavins, thearubigins.
  • Select combination products: Theanine SereneT (theanine, valerian, taurine).

Background
  • Theanine is an amino acid found naturally in tea. Besides caffeine, theanine has been identified as a major component of tea. While younger and fresher tea leaves tend to be richer in caffeine, older leaves tend to have higher theanine levels; furthermore, the withering process of tea production also increases theanine content.
  • Some evidence suggests that theanine affects mental performance and reduces blood pressure. Research has examined the cognitive effects of this substance alone and when combined with caffeine.

Evidence Table

These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider. GRADE *


Theanine has historically been used as a relaxing agent. Limited research suggests that theanine may have a slight relaxing effect but not significantly reduce anxiety. Additional research is needed in this area.

C


Limited research suggests that theanine may counteract the effect of caffeine on blood pressure. Additional research is needed in this area.

C


The mood effect of theanine has been examined when combined with caffeine. Theanine alone had few effects on mood. The combination of theanine and caffeine had improved mood effects not seen with either treatment alone. Additional research is needed in this area.

C


The effect of theanine on cognition (mental performance) has been examined when combined with caffeine. Theanine alone slowed overall reaction time. The combination of theanine and caffeine had improved mood effects not seen with either treatment alone. Additional research is needed in this area.

D
* Key to grades

A: Strong scientific evidence for this use
B: Good scientific evidence for this use
C: Unclear scientific evidence for this use
D: Fair scientific evidence for this use (it may not work)
F: Strong scientific evidence against this use (it likley does not work)


Tradition / Theory

The below uses are based on tradition, scientific theories, or limited research. They often have not been thoroughly tested in humans, and safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider. There may be other proposed uses that are not listed below.

  • Anti-aging, antibacterial, antioxidant (protects against damage caused by chemicals known as free radicals), antitumor, blood vessel disorders, bone marrow suppression, brain injuries, cancer, cerebral ischemia (decreased blood supply to the brain), heart disease, high cholesterol, hypertriglyceridemia (excess fats in the blood), liver cancer, liver toxicity, multidrug resistance, neurological disorders, obesity/weight loss, stress reduction.

Dosing

Adults (18 years and older)

  • For anxiety, a single dose of 200 milligrams of Suntheanine® has been taken by mouth. L-theanine is thought to be most effective for stress and anxiety in the range of 50-200 milligrams, with effects being felt within 30 minutes and lasting for 8-10 hours. It has been suggested that a maximum dose is 1,200 milligrams daily. However, additional research is needed in this area.
  • For blood pressure control, a single dose of 200 milligrams theanine has been taken by mouth.
  • For cognition (mental performance), a single dose of 200-250 milligrams has been taken by mouth.
  • For mood, a single dose of 200-250 milligrams has been taken by mouth.

Children (under 18 years old)

  • There is no proven safe or effective dose for theanine in children.

Safety

The U.S. Food and Drug Administration does not strictly regulate herbs and supplements. There is no guarantee of strength, purity or safety of products, and effects may vary. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy. Consult a healthcare provider immediately if you experience side effects.

Allergies

  • Avoid with known allergy or hypersensitivity to theanine.

Side Effects and Warnings

  • Theanine may be safe at a single dose of 200-250 milligrams, up to a maximum dose of 1,200 milligrams daily.
  • Theanine may negatively affect mental status.
  • Use cautiously in people at risk of developing headaches, as an increase in the "headache" rating using the Caffeine Research Visual Analog Scales was noted.
  • Theanine may lower blood pressure. Caution is advised in people with low blood pressure, and in those taking drugs, herbs, or supplements that affect blood pressure. Blood pressure levels may need to be monitored by a qualified healthcare professional, including a pharmacist. Medication adjustments may be necessary.
  • Avoid use in amounts higher than those normally found in foods.
  • Avoid use in people that are pregnant or breastfeeding, due to a lack of safety data.
  • Avoid in people with known allergy or hypersensitivity to theanine.

Pregnancy and Breastfeeding

  • There is currently a lack of available scientific evidence on the use of theanine in pregnant or breastfeeding women.

Interactions

Interactions with Drugs

  • Theanine may cause low blood pressure. Caution is advised when using medications that may also lower blood pressure. People taking drugs for blood pressure should be monitored closely by a qualified healthcare professional, including a pharmacist. Medication adjustments may be necessary.
  • Theanine may also interact with anticancer agents (Adriamycin®, cisplatin, doxorubicin, idarubicin, and pirarubicin), caffeine, dopamine agonists, dopamine antagonists, drugs that affect GABA (serotonin, dopamine, and gamma-aminobutyric acid (GABA)), drugs that affect the immune system, norepinephrine-dopamine reuptake inhibitors, neurologic agents, psychoactive agents, selective serotonin reuptake inhibitors, or serotonin-norepinephrine reuptake inhibitors.

Interactions with Herbs and Dietary Supplements

  • Theanine may cause low blood pressure. Caution is advised in people taking herbs or supplements that lower blood pressure.
  • Theanine may also interact with anticancer herbs and supplements, caffeine, dopamine agonists, dopamine antagonists, herbs and supplements that affect the immune system, neurologic herbs and supplements, psychoactive herbs and supplements, and selective serotonin reuptake inhibitors.

Attribution
  • This information is based on a systematic review of scientific literature edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (www.naturalstandard.com).

Bibliography
  1. Bryan J. Psychological effects of dietary components of tea: caffeine and L-theanine. Nutr Rev 2008;66(2):82-90.
  2. Cooper R, Morre DJ, Morre DM. Medicinal benefits of green tea: Part I. Review of noncancer health benefits. J Altern Complement Med 2005;11(3):521-528.
  3. Dimpfel W, Kler A, Kriesl E, et al. Source density analysis of the human EEG after ingestion of a drink containing decaffeinated extract of green tea enriched with L-theanine and theogallin. Nutr Neurosci 2007;10(3-4):169-180.
  4. Friedman M, Mackey BE, Kim HJ, et al. Structure-activity relationships of tea compounds against human cancer cells. J Agric Food Chem 2007;55(2):243-253.
  5. Gomez-Ramirez M, Higgins BA, Rycroft JA, et al. The deployment of intersensory selective attention: a high-density electrical mapping study of the effects of theanine. Clin Neuropharmacol 2007;30(1):25-38.
  6. Haskell CF, Kennedy DO, Milne AL, et al. The effects of L-theanine, caffeine and their combination on cognition and mood. Biol Psychol 2008;77(2):113-122.
  7. Kakuda T. Neuroprotective effects of the green tea components theanine and catechins. Biol Pharm Bull 2002;25(12):1513-1518.
  8. Kimura K, Ozeki M, Juneja LR, et al. L-Theanine reduces psychological and physiological stress responses. Biol Psychol 2007;74(1):39-45.
  9. Lu K, Gray MA, Oliver C, et al. The acute effects of L-theanine in comparison with alprazolam on anticipatory anxiety in humans. Hum Psychopharmacol 2004;19(7):457-465.
  10. Nathan PJ, Lu K, Gray M, et al. The neuropharmacology of L-theanine(N-ethyl-L-glutamine): a possible neuroprotective and cognitive enhancing agent. J Herb Pharmacother 2006;6(2):21-30.
  11. Netsch MI, Gutmann H, Luescher S, et al. Inhibitory activity of a green tea extract and some of its constituents on multidrug resistance-associated protein 2 functionality. Planta Med 2005;71(2):135-141.
  12. Nobre AC, Rao A, Owen GN . L-theanine, a natural constituent in tea, and its effect on mental state. Asia Pac J Clin Nutr 2008;17 Suppl 1:167-168.
  13. Rogers PJ, Smith JE, Heatherley SV, et al. Time for tea: mood, blood pressure and cognitive performance effects of caffeine and theanine administered alone and together. Psychopharmacology (Berl) 2008;195(4):569-577.
  14. Sugiyama T, Sadzuka Y. Theanine and glutamate transporter inhibitors enhance the antitumor efficacy of chemotherapeutic agents. Biochim.Biophys.Acta 12-5-2003;1653(2):47-59.
  15. Yamada T, Terashima T, Okubo T, et al. Effects of theanine, r-glutamylethylamide, on neurotransmitter release and its relationship with glutamic acid neurotransmission. Nutr Neurosci 2005;8(4):219-226.

Copyright © 2011 Natural Standard (www.naturalstandard.com)


The information in this monograph is intended for informational purposes only, and is meant to help users better understand health concerns. Information is based on review of scientific research data, historical practice patterns, and clinical experience. This information should not be interpreted as specific medical advice. Users should consult with a qualified healthcare provider for specific questions regarding therapies, diagnosis and/or health conditions, prior to making therapeutic decisions.

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