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Green Tea & Theanine
Drinking a nice hot
cup of green tea can almost always make you feel better. But did you
know that certain natural components of green tea have a direct effect
on the body, increasing relaxation, easing depression and otherwise
improving the mood? A growing body of evidence indicates that both green
tea catechins and theanine, an amino acid found in green tea, can
bring about positive changes to both body and mind.
Animal studies have
found that the catechins increase insulin sensitivity, which means they
help insulin do a better job of delivering glucose to the cells,
including the cells of the brain. This is important because the brain
runs on glucose, and when glucose levels fall too low, you can become
depressed, fatigued, irritable and just plain moody. (Just think about
how your mood disintegrates when you get overly hungry!)
But perhaps the most important
mood enhancer found in green tea is theanine, the amino acid that gives
the tea its mellow taste. Theanine has been shown to
reduce mental and physical stress and promote feelings of relaxation.
One human study found a significant increase
in alpha-brain wave activity (that “relaxed yet alert” state cultivated
in yoga class) after volunteers took 200 mg of theanine dissolved in
water.1 In another human study, theanine decreased two of the
body’s responses to stress – heart rate and salivary immunoglobulin A.2
And in animals given an intravenous dose of theanine following a
dose of caffeine, the theanine calmed the "jittery" effects of the
caffeine.3 No wonder you don’t get the same “buzz” from
green tea that you do from other caffeine-containing drinks!
Tests performed on animals
give two clues as to how theanine affects the brain and helps improve
the mood. First, it significantly increases the brain’s levels of
dopamine and serotonin, neurotransmitters that are linked to a sense of
well-being. And second, theanine releases GABA (gamma amino
butyric acid) in the brain, which calms brain over-excitation, eases
anxiety and promotes relaxation.
Theanine works best
at doses of 50-200 mg, with effects typically being felt within 30
minutes of ingestion and lasting for 8-10 hours. Coincidentally, there’s
about 50 mg. of theanine in one cup of green tea. So have a cup and
relax!
(For more on green
tea's effects on stress, click here.)
Footnotes:
1)
Ito K, Nagato Y, Aoi N, et al. Effects of L-theanine on the release of
alpha-brain waves in human volunteers. Nippon Nogeikagaku Kaishi
1998;72:153-157.
2)
Kimura K, Ozeki M, Juneja LR, Ohira H. L-theanine reduces psychological
and physiological stress responses. Biol Psychol 2007;74(1):39-45.
3)
Kakuda T, Nozawa A, Unno T, et al. Inhibiting effects of theanine upon
caffeine stimulation evaluated by EEG in the rat. Biosci Biotechnol
Biochem 2000; 64:287-293.
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Nadine Taylor, M.S., R.D. presents
GreenTeaLibrary.com,
the most comprehensive collection of scientific information
describing the health benefits of green tea.
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