Saturday, August 15, 2009


What is it?

Theanine is a unique amino acid found in the leaves of green tea (Camellia sinensis). Theanine is quite different from the polyphenol/ and catechin antioxidants for which green tea is typically consumed. In fact, through the natural production of polyphenols, the tea plant converts theanine into catechins. This means that tea leaves harvested during one part of the growing season may be high in catechins (good for antioxidant benefits), while leaves harvested during another time of year may be higher in theanine (good for anti-stress and cortisol-controlling effects). Three to four cups of green tea are expected to contain 100–200 mg of theanine.


Because of theanine’s effects on the brain, common claims include:

•Improved mental focus

•Sounder, more restful sleep

•Better control of stress

Other claims for theanine may include:

•Benefits in cancer therapy

•Reduces blood pressure


The unique aspect of theanine is that it acts as a non-sedating relaxant to help increase the brain’s production of alpha-waves (those associated with “relaxed alertness”). This makes theanine extremely effective for combating tension, stress, and anxiety—without inducing drowsiness. By increasing the brain’s output of alpha waves, theanine is thought to control anxiety, increase mental focus, improve concentration, and promote creativity.


Research studies are quite clear on the facts that people who produce more alpha brain waves also have less anxiety; that highly creative people generate more alpha waves when faced with a problem to solve; and that elite athletes tend to produce a burst of alpha waves on the left side of their brain during their best performances.

In addition to being considered a “relaxing” substance (in adults), theanine has also been shown to have benefits for improving learning performance (in mice), and promoting concentration (in students). One of the most unique aspects of theanine activity is its ability to increase the brain’s output of alpha waves. Alpha waves are one the four basic brain brain-wave patterns (delta, theta, alpha, and beta) that can be monitored using an electroencephalogram (EEG). Each wave pattern is associated with a particular oscillating electrical voltage in the brain, and the different brain brain-wave patterns are associated with different mental states and states of consciousness (Theta = Drowsiness; Alpha = Relaxed/Alertness; Beta = Stress/Anxiety).

A handful of studies (in rats) have shown theanine to be an effective anti-hypertension agent. In these studies, it is interesting to note that theanine was able to bring elevated blood pressure back toward normal levels, but it had no effect in reducing normal blood pressure levels.

There are also more than a dozen reports in the scientific literature which show a clear benefit of theanine in fighting various forms of experimental cancer. In many of these studies, theanine has been shown to enhance the anti-tumor activity of some cancer drugs such as pirarubicin, doxorubicin and adriamycin. It appears that theanine slows the ability of the tumor cells to eject the cancer drugs – so combination therapy with the chemotherapy agent plus theanine seems to maintain high levels of the drug in the tumor cells and both slow their growth and accelerate their death.


No adverse side effects are associated with theanine consumption (3–4 cups of green tea are expected to contain 100–200 mg of theanine) – making it one of the leading natural choices for promoting relaxation without the sedating effects of depressant drugs and herbs. When considering the potential benefits of theanine as an anti-stress or anti-cortisol supplement, it is important to distinguish its non-sedating relaxation benefits from the tranquilizing effects of other “relaxing” supplements such as valerian and kava, which are actually mild central central-nervous nervous-system depressants.


Clinical studies show that theanine is effective in dosages ranging from 50 to 200 mg per day (about what you would find in 2-4 cups of green tea). Because theanine reaches its maximum levels in the blood between 30 thirty minutes and 2 two hours after taking it, it can be used as both as a daily anti-stress and mental-focus regimen and “as needed” as a supplement during stressful times.


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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 Oct 1;158(2):119-24.

7.Sadzuka Y, Sugiyama T, Suzuki T, Sonobe T. Enhancement of the activity of doxorubicin by inhibition of glutamate transporter. Toxicol Lett. 2001 Sep 15;123(2-3):159-67.

8.Sadzuka Y, Yamashita Y, Sugiyama T, Sonobe T. Effect of dihydrokainate on the antitumor activity of doxorubicin. Cancer Lett. 2002 May 28;179(2):157-63.

9.Sugiyama T, Sadzuka Y, Tanaka K, Sonobe T. Inhibition of glutamate transporter by theanine enhances the therapeutic efficacy of doxorubicin. Toxicol Lett. 2001 Apr 30;121(2):89-96.

10.Sugiyama T, Sadzuka Y. Combination of theanine with doxorubicin inhibits hepatic metastasis of M5076 ovarian sarcoma. Clin Cancer Res. 1999 Feb;5(2):413-6.

11.Sugiyama T, Sadzuka Y. Enhancing effects of green tea components on the antitumor activity of adriamycin against M5076 ovarian sarcoma. Cancer Lett. 1998 Nov 13;133(1):19-26.

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14.Yokogoshi H, Terashima T. Effect of theanine, r-glutamylethylamide, on brain monoamines, striatal dopamine release and some kinds of behavior in rats. Nutrition. 2000 Sep;16(9):776-7.

15.Yokogoshi, H., Kato, Y., Sagesaka, Y. M., Takihara-Matsuura, T., Kakuda, T., Takeuchi, N. “Reduction Effect of Theanine on Blood Pressure and Brain 5-Hydroxyindoles in Spontaneously Hypertensive Rats.” Biosciences, Biotechnology, and Biochemistry, April 1995, 59(4): 615–18.

16.Yokogoshi, H., Terashima, T. “Effect of Theanine, R-Glutamylethylamide, on Brain Monoamines, Striatal Dopamine Release and Some Kinds of Behavior in Rats.” Nutrition, Sept. 2000, 16(9): 776–77.

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

EDITOR'S NOTE: This monograph can be found in The Health Professional's Guide to Dietary Supplements (Lippincott, Williams & Wilkins) by Shawn M. Talbott, PhD and Kerry Hughes, MS.

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