L-Theanine:
How a Unique Anxiety Reducer and Mood Enhancer Increases Alpha
Waves and Alertness as seen in
Infinite Play the
Movie
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.
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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)
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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.
Highly recommended
source for this nutrient and other
supplements.
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.
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