What Is It?

Health Benefits
Dosage Information

Guidelines for Use

General Interaction

Possible Side Effects


Evidence Based Rating Scale

What Is It?

Since the import of small-leaf Chinese variety tea (Camellia sinensis var. sinensis) in the 8th century to Japan, the Japanese people have cultivated and popularized the consumption of this invigorating brew. In the West, science is only beginning to scratch the surface of discovering the properties and powerful antioxidants present in this ancient beverage.

Health Benefits

Theanine makes up about 50% of the dry protein weight of tea leaves (1). This compound closely mirrors the chemical structure of glutamic acid, an excitatory neurotransmitter in the brain. Theanine also contains antigens that prime the body’s immunological response to both known pathogens and strains that you have not yet encountered.

Specifically, Theanine may help to:

·  Enhance the efficacy of anti-tumor drugs. Several studies have shown theanine to inhibit tumor growth and increase the levels of doxorubicin, cisplatin, and irinotecan inside tumors (2-8). As an added benefit theanine seems to play a part in protecting normal tissues from absorbing cancer drugs. In the future clinical researchers postulate that theanine may be a valuable adjunct to conventional chemotherapy.

·  Prevent and decrease the size of blood clots in stroke. The neuroprotective properties of green tea are attributed in large part to theanine’s ability to influence glutamate binding and transport in the brain. After stroke an excess amount of glutamate in the space between brain cell receptors is postulated to lead increased neuronal death. In this study, mice pretreated with an injection of theanine showed less brain cell death after cerebral infarct (stroke) (9-11). In fact the more theanine that a mouse was injected with before stroke, the more brain cells that survived the stroke intact. Thus further studies are warranted to ascertain how theanine can help in the reduction of brain damage after stroke.

·  Reduce high blood pressure. Preliminary studies in mice have shown that administering theanine decreased cases of spontaneous hypertension significantly. More studies are needed to determine theanine’s mechanism of action before studies on human beings with hypertension are allowed (12).

·  Protect cells from oxidative stress. The antioxidative properties of green tea can be attributed to the high levels of catechins and theanine in green tea. Researchers postulate that one of the onset mechanisms for arteriosclerosis (the hardening of the arteries due to build up of calcium) maybe the oxidation of low-density lipoprotein (LDL) by an active oxygen species (10). As blood vessels lose their natural elasticity this puts you at greater risk for blood clots that can cause heart attack and stroke. These oxidative alterations have been shown to be preveted by tea catechins. More research is necessary to determine the mechanism by which tea works to protect our cells from damage free radicals.

·  Promote weight loss. A recent animal study demonstrated that the combination of theanine, catechins, and caffeine in green tea helped to reduce concentrations of triglycerides and non-esterified fatty acids in blood serum (13). These effects suppressed fat accumulation and weight gain in mice. Scientists must now investigate if these findings remain consistent in a human population.

·  Increase resistance to bacteria. The National Academies of Science conducted a study on how theanine acts in vitro on the immunological functions of the body. Their study data showed that drinking tea containing theanine may prime the immune system’s T cells to respond to microbial attack(14). More studies are needed to determine the full extent theanine’s natural ability to protect against infection.  

·  Promote relaxation. Direct injection of theanine increases the release of serotonin and dopamine, which are chemicals in the brain associated with positive emotions and relaxation (15). Having green tea in the morning instead of coffee may be more than just a calming ritual – it may actually produce an extra emotional boost to start your day off right!


  • tea
  • injection
  • capsule

      Dosage Information

      Special tip: Not all green teas will contain the same amount of theanine. The highest quality of Chinese tea is Longjing type tea. Researchers in the UK found higher levels of theanine in Longjing type tea(16). Another high quality type of green tea is Sencha. For best results buy high-quality teas from a respectable distributor. This will ensure that you are getting the greatest amount of benefit from adding green tea to your diet.

      · For greater medicinal benefit buy loose leaf tea, as opposed to tea bags. Loose leaf tea is of a higher quality and undergoes less of the oxidative processing that causes tea to loose its medicinal benefits.

      · Current studies show that theanine is effective in dosages ranging from 50 to 200 mg per day. This is the amount in roughly 2 to 4 cups of green tea a day. Since theanine is absorbed into the bloodstream through the intestinal tract it is important to note that reaches maximum levels in your body anywhere from 30 minutes to 2 hours after ingestion.

      Be sure to check out our Dosage Recommendations Chart for Theanine, which lists therapeutic dosages for specific ailments at a glance.

      Guidelines for Use

      To ingest theanine as a component of green tea: Purchase tea from a quality retailer to ensure adequate levels of theanine. Heat water and steep tea bag for 1 to 3 minutes depending on personal preference. The longer you steep the tea bag/ infuser the more pungent your tea.

      General Interaction

    • Theanine has not been shown to interact adversely with other prescription drugs or herbal supplements. As always discuss any change in your diet or supplement routine with your doctor.

      Possible Side Effects

      No adverse side effects from theanine consumption have been documented.


      Theanine has been shown to help in the fight against cancer however, it is not a substitute for conventional chemotherapy. Theanine is best used as adjunctive therapy to conventional cancer treatment.


      1. Sugiyama T, Sadzuka Y. Theanine and glutamate transport inhibitors enhance the antitumor efficacy of chemotherapeutic agents. Biochem Biophys Acta. 2003; 1653(2):47-59.

      2. Sadzuka Y, Yamashita Y, Kishimoto S, Fukushima S, Takeuchi Y, Sonobe T. Glutamate transporter mediated increase of antitumor activity by theanine, an amino acid in green tea. Yakugaku Zasshi. 2002;122(11):995-9.

      3. Zhang G, Miura Y, Yagasaki K. Effects of dietary powdered green tea and theanine on tumor growth and engogenous hyperlipidemia in hepatoma-bearing rats. Biosci Biotechnol Biochem. 2002;66(4):711-6.

      4. Sadzuka Y, Sugiyama T, Suzuki T, Sonobe T. Enhancement of the activity of doxorubicin by inhibition of glutamate transporter. Toxicol Lett. 2001;123(2-3):159-67.

      5. Sugiyama T, Sadzuka Y, Tanaka K, Sonobe T. Inhibition of glutamate transporter by theanine enhances the therapeutic efficacy of doxorubicin. Toxicol Lett. 2001;121(2):89-96.

      6. Sadzuka Y, Sugiyama T, Sonobe T. Improvement of idarubicin induced antitumor activity and bone marrow suppression by theanine, a component of tea. Cancer Lett. 2000; 158(2):119-24.

      7. Sadzuka Y, Sugiyama T, Sonobe T. Efficacies of tea components on doxorubicin induced antitumor activity and reversal of multidrug resistance. Toxicol Lett. 2000;114(1-3):155-62.

      8. Egashira N, Hayakawa K, Mishima K, Kimura H, Iwasaki K, Fujiwara M. Neuroprotective effect of gamma-glutamyethylamide (theanine) on cerebral infarction in mice. Neurosci Lett. 2004;363(1):58-61.

      9. Kakuda T. Neuroprotective effects of the green tea components theanine and catechins. Biol Pharm Bull. 2002;25(12):1513-8. \

      10.Kakuda T, Yanase H, Utsunomiya K, Nozawa A, Unno T, Kataoka K. Protective effect of gamma-glutamyethylamide (theanine) on ischemic delayed neuronal death in gerbils. Neurosci Lett. 2000;289(3):189-92.

      11. Yokogoshi H, Kobayashi M. Hypotensive effect of gamma-glutamyethylamide in spontaneously hypertensive rats. Life Sci. 1998;62(12):1065-8.

      12. Zheng G, Sayama K, Okubo T, Juneja LR, Oguni I. Anti-obesity effects of three major components of green tea, catechins, caffeine, and theanine, in mice. In Vivo. 2004;18(1):55-62.

      13. Kamath AB, Wang L, Das H, Li L, Reinhold VN, Bukowski JF. Proc Natl Acad Sci USA. 2003;100(10):6009-14.

      14. Yokogoshi H, Kobayashi M, Mochizuki M, Terashima T. Effect of theanine, r-glutamylethylamide, on brain monoamines and striatal dopamine release in conscious rats. Neurochem Res. 1998;23(5):667-73.

      15.Le Gall G, Colquhoun IJ, Deferenz M. Metabolite profiling using (1)H NMR  spectroscopy for quality assessment of green tea, Camellia sinensis(L.). J Agric Food Chem. 2004;52(4):692-700.


      Evidence Based Rating Scale 

      The Evidence Based Rating Scale is a tool that helps consumers translate the findings of medical research studies with what our clinical advisors have found to be efficacious in their personal practice. This tool is meant to simplify which supplements and therapies demonstrate promise in the treatment of certain conditions. This scale does not take into account any possible interactions with any medication/ condition/ or therapy which you may be currently undertaking. It is therefore advisable to ask your doctor before starting any new treatment regimen.
























      Favorable results in patients indicate efficacy in promoting relaxation. Preliminary trials indicate need for further research to confirm or refute these findings.






      Heart Disease Prevention 





      Date Published: 09/08/2005
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