A natural glutamate antagonist is the structurally similar amino acid L-theanine. The similarity enables L-theanine (L-Glutamic acid-?-monoethylamide) to physically block glutamate, thus preventing calcium ion induced hyperexcitability. Although researchers aren’t positive how theanine works yet, they theorize that theanine blocks the NMDA receptor which is the doorway that glutamate uses to enter cells. Theanine is known to increase GABA (Gamma-Amino-Butyric Acid), an important inhibitory neurotransmitter. Because of the similar structure, theanine can also fit in this doorway, blocking access to glutamate. But, although it can fit in the doorway, theanine does not have the same effect on the cell as glutamate does. Rather than causing damage, theanine acts like a shield against damage. Theanine is the active ingredient in green tea. The Japanese have used enormous amounts of MSG for many years to improve taste of poor quality food, but they offset its toxic effects with green tea. In 1964, Japan approved theanine?s use in all food, except baby food. In Japan, you can buy over 50 different food items that contain theanine. Japanese soft drinks are spiked with the relaxant, and it has been put into chewing gum. The tranquilizing effects of theanine definitely are not imaginary. Theanine readily crosses the blood-brain barrier of humans and exerts subtle changes in biochemistry. An increase in brain alpha waves (resulting in an increase in wakeful relaxation) has been documented, and the effect has been compared to getting a massage or taking a hot bath. And, unlike tranquilizing drugs (including kava-kava, valerian and St. John’s wort), it doesn’t interfere with the ability to either think or exercise good judgement. It does not sedate, as demonstrated by no change in brain theta waves upon administration. It does not help one doze or fall asleep, unless the person is excited or hyper. By shutting down the “worry” mode, L-theanine increases concentration and focuses thought. This is the concept behind the Japanese tea ceremony which causes a person to focus on the moment. Dosage is reported to be 100 mg 1 to 4 times per day.