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Theanine: a useful and a supplement, generally recognized as safe (GRAS)

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What kinds of theanine do we get on the market?

There are two sorts of supplements available on the market:

1. a synthetic form, mostly branded under the name Suntheanine and consisting of  purified L-theanine which is derived from chemical, enzymatic synthesis and

2. a pure natural form, l-theanine, consisting of the natural aminoacid in tea leaves and produced by a natural fermentation process of these tea leaves.

The subject ingredient of tea leaves, the compound L-theanine, is an amino acid which is also known under different names,  y-glutamylethylamide or N-ethyl-L-glutamine.

L-theanine
occurs in tea-leaves and is soluble in hot water

L-Theanine is
naturally occurring at high concentrations in the leaves of the green tea
plant, Camellia sinensis.

L- Theanine
accounts for approximately I-2% of the dry weight of tea leaves and is
water-soluble. Steeping C. sinensis leaves in hot water creates tea, the most
commonly consumed beverage in the world. After steeping, the majority of
theanine is solubilized and can easily enter the body via the stomach and the
guts.

How to make
natural L-theanine

If we do not
want l-theanine via chemical synthesis, we can isolate l-theanine from tea
leaves. How does such an isolation takes place?

Theanine, which
as we saw is water soluble, can be naturally extracted from the leaves by
incubating the leaves with water at around sixty degrees Celsius for some
hours. The extract can then be concentrated, centrifuged, isolated and purified
through membrane ultrafiltration to a very high degree of purity.

L-theanine is
very stable and does not deteriorate after years

Once in a
capsule, l-theanine is a very stable compound, and even at high temperature it
does not become unstable or degrades. The so called shelf life of theanine has
been found to be at least 2 years.

Amount of
l-theanine intake each day and recommended dose

In the form of
tea, theanine is a widely consumed ingredient which has been a part of the
human diet for thousands of years. World tea production in 2001 has been
reported to be 3.02 million tons.

Based on a 2003
world population of about 6.2 billion, per capita consumption of 120 mL of tea
equates to daily consumption of nearly a million metric tons of tea. Thus, the
available evidence suggests that there is a common exposure to tea and to its
constituent, L-theanine. Despite this long history, no adverse effects due to
ingestion of tea or L-theanine have been reported. L-Theanine has also been
used as a dietary supplement in the US since the 1990s without any reports of
adverse effects.

Recent studies by Kat et al. (2003) and Ekborg-Ott et al. ( I997) found the average theanine concentration
among tea varieties was approximately
1.4%. A typical cup of tea uses 3 g of tea leaves, which contains about 30 mg of theanine.

Based on the typical
concentration of L-theanine in tea
(1-2.5%), in the estimated daily intake of
L-theanine from tea was determined to be between
153 and 382 mg/person/day at the mean and between 330 and 825 mg/person/day at the 90th percentile.

These estimates indicate that the estimated daily intake of L-theanine
between 450-900 mg/day corresponds with the levels of L-theanine currently
consumed by the heaviest tea drinkers in the United States. Thus it is
perfectly safe to ingest each day 3 times 150 mg to 6 times 150 mg capsules.

How come theanine protects cells and even neurons in the brain?

Since L-theanine crosses the blood-brain
barrier, and is an analog of the major excitatory neurotransmitter glutamate, a
number of studies have examined the effects of L-theanine on neuraltissues.

Research has shown that L-theanine is
capable of binding to both glutamate receptors and glutamate transporters.

Glutamate receptors are mostly found in
the post-synaptic cells, and are responsible for transmitting the excitatory
glutamate signal. The glutamate transporters are mostly found in neuronal and
glial cells; they remove glutamate from the extracellular synaptic space and
help to regulate glutamate levels and thus neuronal signaling. In brain injury
and disease, an excess of glutamate causes oxidative damage, known as
excitotoxicity, which can ultimately lead to neuronal cell death.

Theanine appears to provide
neuroprotection by reducing levels of glutamate, thus inhibiting
glutamate-induced excitotoxicity.

Research studies have shown that theanine
binds to two glutamate receptors,
  both
the so called ionotropic and metabotropic glutamate receptors. The first
receptor arranges ions to stream in and out off neurons, the second receptor
initiates metabolic activity in the cells.

The ionotropic glutamate receptors conduct
neuronal signals through ligand-gated ion channels.
     

In an early study, Shinozaki and lshida
(1978) reported that theanine functions as a glutamate antagonist at the
crayfish neurom uscularj unction. Later, Kakuda et al. (2000) demonstrated that
theanine provided dose-dependent protection from ischemic delayed neuronal
death induced by glutamic acid in brainfield CAI of the gerbil hippocampus.

Theanine literature 

Blumberg, J. (2003). Introduction to the proceedings of the third international scientific symposium on tea and human

health:roleofflavonoidsinthediet. JNutr133(Suppl):3244s-3246s.

Borzelleca, J. F., D. Peters, Hall, W., 2006. A 13-week dietary toxicity and toxicokinetic study with I-theanine in rats. Food Chem Toxicol44(7): 1158-66.

Egashira, N., Hayakawa, K., Mishima, K., Kimura, H., Iwasaki, K., Fujiwara, M., 2004. Neuroprotective effect of gamma-glutamylethylamide (theanine) on cerebral infarction in mice. Neurosci Lett 363(1):58-61.

Graham, H.N., 1992. Green tea composition, consumption, and polyphenol chemistry. Prev Med 21: 334-350. 

Kakuda,T.,Yanase,H.,Utsunomiya,K.,Nozawa,A.,Unno,T.,Kataoka,K.,2000. Protective effect of gamma- glutamylethylamide (theanine) on ischemic delayed neuronal death in gerbils. Neurosc iLett289(3):189-192. 

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