L-Theanine: How a Unique Anxiety Reducer and Mood Enhancer Increases Alpha Waves and Alertness
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by Carolyn Perrini, CLS, CNC

Hundreds of studies exist showing the many health benefits of green tea. But what makes it the most consumed beverage in the world after water is its pleasant taste and relaxation effect. Both of these qualities—and more—can be traced to a unique, neurologically-active amino acid in tea called L-theanine (gamma-ethylamino-L-glutamic acid).

L-theanine is a free (non-protein) amino acid found almost exclusively in tea plants (Camellia sp.), constituting between 1 and 2-percent of the dry weight of tea leaves. It is the predominant amino acid in green tea leaves, giving tea its characteristic umami or "5th taste" (besides the four traditional tastes: sweet, salty, acid, and bitter). Attempts to isolate the L-theanine, with its physical and neurological benefits, from the tea leaves were once difficult, expensive, and inefficient. Economically feasible methods of producing the identical L-theanine now exist and do not require a mountain of tea leaves.

Physiological Effects
The calming effect of green tea may seem contradictory to the stimulatory property of tea's caffeine content but it can be explained by the action of L-theanine. This amino acid actually acts antagonistically against the stimulatory effects of caffeine on the nervous system. (1) Research on human volunteers has demonstrated that L-theanine creates a sense of relaxation in approximately 30-40 minutes after ingestion via at least two different mechanisms. First, this amino acid directly stimulates the production of alpha brain waves, creating a state of deep relaxation and mental alertness similar to what is achieved through meditation. Second, L-theanine is involved in the formation of the inhibitory neurotransmitter, gamma amino butyric acid (GABA). GABA influences the levels of two other neurotransmitters, dopamine and serotonin, producing the key relaxation effect. (2)

Alpha Brain Activity
The brain emits weak electrical impulses (brain waves) that can be measured on the surface of the head. The predominant frequency of electrical impulses correlates with different types of mental states and activities. Brain waves are classified into four categories (delta, theta, alpha, and beta)—each with an associated mental state (Fig. 1). Delta is seen only in the deepest stages of sleep. Theta is seen in light sleep and drowsiness. Alpha is present in wakefulness where there is a relaxed and effortless alertness and Beta is seen in highly stressful situations and where there is difficulty in mental concentration and focus. It is well known that alpha brain waves are generated during a relaxed state and therefore alpha waves are used as an index of relaxation