L-Theanine: How a Unique Anxiety Reducer and Mood Enhancer Increases Alpha Waves and Alertness
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.
In one study of these mental responses to L-theanine, brain wave
topography showed that alpha waves were observed from the back to the
top of a person's head (occipital and parietal regions of the brain)
within approximately 40 minutes after the subjects had taken either 50
or 200 mg of L-theanine. In a separate study, the intensity of alpha
waves were determined to be dose dependent (with a 200 mg dose showing a
significant increase over controls) and detectable after 30 minutes.
(2,3)
Additional Benefits
L-theanine has a significant effect on the release or reduction of
neurotransmitters like dopamine and serotonin, resulting in improved
memory and learning ability. L-theanine may also influence emotions due
to its effects on the increased release of dopamine. L-theanine reduces
brain serotonin concentration by either curtailing serotonin synthesis
or increasing degradation in the brain.
The regulation of blood pressure is partly dependent upon
catecholaminergic and serotonergic neurons in both the brain and the
peripheral nervous system. Studies on spontaneously hypertensive rats (SHR)
showed an impressive blood pressure lowering effect with L-theanine. The
lowered blood pressure effect was dose-dependent with the highest test
dose creating the most significant drop. L-glutamine was used as one of
the controls. Although L-glutamine is similar in chemical structure to
L-theanine, it did not exhibit an anti-hypertensive effect
(Fig. 2). (3)
Preliminary studies report that L-theanine has been found to increase
the anti-tumor activity of some chemotherapeutic agents (doxorubicin and
idarubicin) and to ameliorate some of the side effects of these drugs.
It appears to increase the inhibitory concentration of these drugs in
the tumor cells, although the mechanism is not known. At the same time,
L-theanine decreased oxidative stress caused by these agents on the
normal cells, possibly due to its mild antioxidant activity. In this
regard, L-theanine has been shown to inhibit lipid peroxidation,
catalyzed by copper, in low-density lipoprotein (LDL) in vitro.
(4)
Stress Relief
Stress and anxiety are debilitating conditions that upset the balance of
our hormones leading to a loss of our well-being, performance, and even
lifespan. Stress impairs the immune system, leaving us vulnerable to
opportunistic infections, and can cause depression. In 1998,
pharmaceutical sales of anti-anxiety drugs totaled over 700 million
dollars, while sales of antidepressants totaled close to 5 billion
dollars! People under stress can mitigate many of the harmful effects of
stress with L-theanine without becoming sedated in the process.
L-theanine doesn't make one drowsy, nor does it promote sleep because
this amino acid does not produce theta waves in the brain. It should be
noted that if an individual were already relaxed, taking L-theanine
would not produce further relaxation.
Status and Usage
L-theanine has just recently been introduced to the U.S. market. Japan
is credited with most of the clinical studies and information we possess
thus far on L-theanine but research is ongoing. We do know that it is
absorbed from the small intestine via a sodium-coupled active transport
process. It crosses the blood-brain barrier, as evidenced by the mental
effects. L-theanine competes for absorption in the intestinal tract and
the brain with the amino acids found in the methionine group (leucine,
isoleucine, and valine), however the concentrations of amino acids are
unchanged by simultaneous ingestion of L-theanine.
L-theanine is extremely safe. There are no dietary limits on
L-theanine intake by the Japan Food Additive Association. In 1964, the
Japanese Ministry of Health and Welfare approved L-theanine for
unlimited use in all foods, with the exception of infant foods.
The intended use of L-theanine is that of a mental and physical
relaxant that does not induce drowsiness. Although there is no set
schedule for taking L-theanine, it may generally be taken at the first
signs of stress. Based on the results of the clinical studies,
L-theanine is most effective in the range of 50-200 mg, with the effect
being felt within 30 minutes and lasting for 8-10 hours. Individuals
with high stress levels may increase their dosage of L-theanine to at
least 100 mg, with no more than 600 mg being taken in a six hour period.
FDA recommends a maximum dose of 1200 mg daily, although the reason for
this limit is not clear, due to its demonstrated safety. There are no
known adverse reactions to L-theanine and no drug interactions have been
reported. L-theanine is not affected by food and may be taken anytime,
as needed. Because it has a mild taste, capsules may be opened and
dissolved in water. Although it is probably safe for pregnant women and
nursing mothers, we discourage its use by them pending conclusive
research.
Conclusion
Research into L-theanine derived from the contradictory observation that
green tea, with its high caffeine content, produces a very calming
effect. The seemingly multi-dimensional reasons for this relaxation
effect will continue to be studied. Current areas of ongoing research
include using L-theanine as an alternative to Ritalin in children and
adults, as a treatment for PMS, in controlling certain conditions of
high blood pressure, in sharpening mental acuity and concentration, and
as an anti-cancer agent alone and in synergy with other cancer-fighting
agents. L-theanine may find another area of application for its use as a
supplement in reducing the negative side effects of caffeine brought on
by the over-consumption of coffee, soft drinks, or other
caffeine-containing substances.
References
1. Kakuda T, Nozawa A, Unno T, et al. Inhibiting effects of theanine on
caffeine stimulation evaluated by EEG in the rat. Biosci Biotechno
Biochem 2000; 64:287-293.
2. Mason R. 200 mg of Zen; L-theanine boosts alpha waves, promotes alert
relaxation. Alternative & Complementary Therapies 2001,April; 7:91-95
3. 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.
4. Yokozawa T, Dong E. Influence of green tea and its three major
components upon low-density lipoprotein oxidation. Exp Toxicol Pathol
1997; 49(5):329-335.
The information in this article is not intended to provide personal
medical advice, which should be obtained from a medical professional,
and has not been approved by the U.S. FDA.
