L-Theanine

 

L-Theanine Clinical Report Summary

Written Exclusively for MyNutritionStore.com by Sarah Dzida 

 

L-theanine has been used as a mood-enhancer and relaxant for years in Japan.  While past studies have mainly focused on the modest antioxidant's proven ability to effectively increase anticancer effects and ameliorate the side effects of anticancer drugs, new research has discovered that L-theanine significantly increases serotonin and/or dopamine in the brain (1-3).  These findings suggest that L-theanine has the potential to enhance learning ability, induce relaxation and relieve emotional stress.  A recent preliminary human study reported positive results on L-theanine's ability to induce relaxation, while a preliminary animal study showed its ability to inhibit caffeine stimulation (1, 2).  However, while researchers believe that L-theanine has shown promising potential, they also believe that more rigorous follow-ups are needed for scientists to fully define its effect.  In contrast, due to several animal and in vitro studies, researchers continue to be supportive of L-theanine's cancer-inhibiting properties (4-8).

 

L-Theanine Overview

 

L-theanine (C₇H₁₄O₃N) is a non-protein amino acid which naturally occurs in the green tea plant and is the main factor behind its distinctive taste.  Making up 1 - 2% of the dry weight in green tea leaves, L-theanine continues to be used as a nutritional supplement for mood modulation in Japan.  Studies show that L-theanine penetrates the blood-brain barrier and increases the serotonin and/or dopamine levels especially in the striatum, hypothalamus and hippocampus (1).   Because L-theanine can penetrate the blood-brain barrier, which protects the brain from chemicals in the bloodstream without inhibiting essential metabolic functions, the amino acid may be able to affect mood, induce relaxation and relieve emotional stress in the body.

 

Safe Use of L-Theanine

 

L-theanine supplements for relaxation and mood available in Japan are measured at doses between 50 and 200 mg.  Persons with a known allergy or hypersensitivity to L-theanine or a product that contains one of its components as well as pregnant women and nursing mothers should avoid the supplement.  Persons who are being treated with cancer chemotherapeutic agents should only use L-theanine under direct medical supervision.

 

Clinical Studies for L-Theanine

 

1. L-Theanine as a Relaxant

 

Inhibiting Effects of Theanine on Caffeine Stimulation Evaluated by EEG in the Rat.  Kaduka et al.

In this study, the inhibiting action of theanine on the excitation by caffeine at the concentration regularly associated with drinking tea was investigated using electroencephalography(EEG) in rats. First, the stimulatory action by caffeine i.v. administration at a level higher than 5.MU.mol/kg (0.970mg/kg) b.w. was shown by means of brain wave analysis, and this level was suggested as the minimum dose of caffeine as a stimulant. Next, the stimulatory effects of caffeine were inhibited by an i.v. administration of theanine at a level higher than 5.MU.mol/kg (0.781mg/kg) b.w., and the results suggested that theanine has an antagonistic effect on caffeine's stimulatory action at an almost equivalent molar concentration. On the other hand, the excitatory effects were shown in the rat i.v. administered 1 and 2.MU.mol/kg (0.174 and 0.348mg/kg) b.w. of theanine alone. These results suggested two effects of theanine, depending on its concentration.

 

L-Theanine -- a unique amino acid of green tea and its relaxation effect in humans. Juneja et al.

From old periods, it is said that drinking green tea brings relaxation. The essential substance, which causes a sense of relaxation, is theanine. Theanine is a unique amino acid as it is found almost solely in tea plants and the main component which is responsible for the exotic taste of green tea. It was found that L-theanine administered to rats intraperitoneally reached the brain within 30 min without any metabolic changes. Theanine also acts as a neurotransmitter in the brain and decreased blood pressure in hypertension rats significantly. In general, animals always generate very weak electric pulse on the surface of brain, called brain waves. Brain waves are classified into four types namely .ALPHA., .BETA., .DELTA. and .THETA.-waves based on the mental conditions. Generation of .ALPHA.-waves is considered as an index of relaxation. In human volunteers, .ALPHA.-waves were generated on the occipital and parietal regions of the brain surface within 40 min after the oral administration of theanine (50-200mg) by the manifest relaxation without causing drowsiness. With the successful industrial production of L-theanine, we are now able to supply Suntheanine (trade name of L-theanine) which offers tremendous opportunity for designing foods and medical foods targeting relaxation and the reduction of stress.

 

2. L-Theanine and Anxiety Reduction

 

Effects of L-Theanine on the Release of Alpha Brain Waves in Human Volunteers.  Kobayashi et al.

L-Theanine is an amino acid found in green tea leaf and in its infusion, and is known to control excitement caused by caffeine. It is also known that the oral administration of L-theanine to rats results in a decrease of serotonin and increase of catecholamines in their brain. L-Theanine has been confirmed to be safe in animal experiments. We found recently that oral intake of L-theanine caused a feeling of relaxation among the human volunteers examined. These observations led us to do experiments on the effects of administration of L-theanine on the brain electric waves. Eight female university students were selected as volunteers. Four of them were ranked to be Grade I (the highest anxiety) and the remaining four, Grade V (the lowest anxiety) in an investigation done by the manifest anxiety scale method. A dose of oral administration of 200 mg of L-theanine dissolved in 100 ml of water resulted in the generation of α-electric waves in the occipital and parietal regions of the brains of the subjects. The emission intensity of α-brain waves (integrated as a function of investigation times and area) was significantly greater in the group of Grade I than that of Grade V. These results indicate the possibility for L-theanine to be applied to foods and beverages as a new type of functional food ingredient for its relaxation effect.

 

3. L-Theanine's Cancer-Inhibiting Properties

 

Efficacies of tea components on doxorubicin induced antitumor activity and reversal of multidrug resistance. Sadzuka et al..

Considering of novel biochemical modulation by some foods and beverages, we have performed screening for green tea components that have enhancing effects on doxorubicin (DOX) induced antitumor activity. Components, such as caffeine, theanine, ( - )-epigallocatechin gallate (EGCG) and flavonoids have inhibitory effects on the DOX efflux from Ehrlich ascites carcinoma cells. Thus, it is suggested that EGCG and flavonoids may enhance DOX induced antitumor activity and increase the DOX concentrations in tumors through the inhibition of DOX efflux. It is expected that these components in green tea exhibit low toxicity and that there are few side effects of drinking green tea in combination with an antitumor agent. We think that the intake of a favorite beverage favors a positive mental attitude of a patient and increases the efficacy of the chemotherapeutic index, and that this efficacy is useful for improving the quality of life on cancer chemotherapy. In DOX resistant P388 leukemia cell bearing mice theanine increased the DOX induced efficacy through an increase in the DOX concentrations in the tumors. Theanine attacked the same transport process for DOX in both types of cells, elevated the DOX concentration and increased the DOX induced antitumor activity.

 

L-Theanine References 

 

1. Juneja LR, Chu D-C, Okubo T, et al. L-Theanine -- a unique amino acid of green tea and its relaxation effect in humans. Trends Food Sci Tech. 1999; 10:199-204.
2. Kaduka T, Nozawa A, Unno T, et al. Inhibiting effects of theanine on caffeine stimulation evaluated by EEG in the rat. Biosci Biotechnol Biochem. 2000; 64:287-293.
3. 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; 23:667-673.
4. Sadzuka Y, Sugiyama T, Miyagishima A, et al. The effects of theanine, as a novel biochemical modulator, on the antitumor activity of adriamycin. Cancer Lett. 1996; 105; 203-209.
5. Sadzuka Y, Sugiyama T, Sonobe T. Efficacies of tea components on doxorubicin induced antitumor activity and reversal of multidrug resistance. Toxicology Lett. 2000; 113:155-162.
6. Sugiyama T, Sadzuka Y. Enhancing effects of green tea components on the antitumor activity of adriamycin against M5076 ovarian carcinoma. Cancer Lett. 1998; 133:19-26.
7. Sugiyama T, Sadzuka Y. Combination of theanine with doxorubicin inhibits hepatic metastasis of M5076 ovarian sarcoma. Clin Cancer Res. 1999; 5:413-416.
8. Sugiyama T, Sadzuka Y, Sonobe T. Theanine, a major amino acid in green tea, inhibits leukopenia and enhances antitumor activity induce by idarubicin. Proc Am Assoc Cancer Res. 1999; 40:10(Abstract 63).
9. Kobayashi K, et al.  1998.  Effects of L-Theanine on the Release of Alpha Brain Waves in Human Volunteers.  Nippon Noegikagaku Kaishi.  72: 153-151.