While some complementary and alternative techniques have been studied scientifically, high-quality data regarding safety, effectiveness, and mechanism of action are limited or controversial for most therapies. Whenever possible, it is recommended that practitioners be licensed by a recognized professional organization that adheres to clearly published standards. In addition, before starting a new technique or engaging a practitioner, it is recommended that patients speak with their primary healthcare provider(s). Potential benefits, risks (including financial costs), and alternatives should be carefully considered. The below monograph is designed to provide historical background and an overview of clinically-oriented research, and neither advocates for or against the use of a particular therapy.
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.
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.
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.
|Blood pressure control
Limited research suggests that theanine may counteract the effect of caffeine on blood pressure. Additional research is needed in this area.
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.
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.
*Key to grades:
The below uses are based on tradition or scientific theories. 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 health care professional.
- 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.
The below doses are based on scientific research, publications, traditional use, or expert opinion. Many herbs and supplements have not been thoroughly tested, and safety and effectiveness may not be proven. Brands may be made differently, with variable ingredients, even within the same brand. The below doses may not apply to all products. You should read product labels, and discuss doses with a qualified healthcare provider before starting therapy.
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.
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.
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.
Most herbs and supplements have not been thoroughly tested for interactions with other herbs, supplements, drugs, or foods. The interactions listed below are based on reports in scientific publications, laboratory experiments, or traditional use. 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.
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.
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).
Natural Standard developed the above evidence-based information based on a thorough systematic review of the available scientific articles. For comprehensive information about alternative and complementary therapies on the professional level, go to www.naturalstandard.com. Selected references are listed below.
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- 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. View Abstract
- 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. View Abstract
- 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. View Abstract
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- 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. View Abstract
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- Kimura K, Ozeki M, Juneja LR, et al. L-Theanine reduces psychological and physiological stress responses. Biol Psychol 2007;74(1):39-45. View Abstract
- 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. View Abstract
- 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. View Abstract
- 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. View Abstract
- 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. View Abstract
- 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. View Abstract
- 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. View Abstract
- 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. View Abstract
Copyright © 2013 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.