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Green tea controls high blood pressure
High blood pressure places a serious
burden on the vascular system and contributes to atherosclerosis.
Atherosclerosis will in turn precipitate heart disease, stroke and other
cardiovascular diseases. The cause of high blood pressure is not yet fully
understood, but it is clear that a chemical called angiotensin II plays a role
in high blood pressure due to essential hypertension and to arterial stenosis of
the kidneys. Blood contains the substance angiotensinogen which is transformed
to angiotensin I unde action of the enzyme renin in the kidneys. Another enzyme
called th "Angiotensin Converting Enzymen (ACE) then changes angiotensin I
t angiotensin II, which is an extremely strong vascular constrictor. It is th
onstriction of the blood vessels caused by this constrictor that leads to high
blood pressure.
Dr. Hara(#9) has shown that green tea catechin impedes the action of ACE and
suppresses production of angiotensin II. He has also demonstrated that
administration of catechin to Spontaneously Hypertensive Rat (SHR) could limit
increases in the rats' blood pressure. SHR are rats used as models for human
high blood pressure experiments, and their blood pressure at the start of the
experiment (when they were five weeks old) was 130 140mmHg. By the age of about
10 weeks, after a diet of normal feed, their blood pressure had risen to more
than 200mmHg. But the blood pressure those rats raised with U.5Y5 catechin added
to their teed remained belo of those rats raised with 0.5% catechin added to
their feed remained below 2OOmmHg. Exchanging the feed of the two rat groups at
16 weeks of age led to a reversal in blood pressure between the two groups (Fig.
3). These results indicate that green tea catechin has the ability to
prevent a rise in blood pressure. If the amount of catechin used in this
experiment is converted to the amount of green tea normally drunk by humans, it
is equivalent to drinking about 10 moderately large cups of tea per day.
These are surely quite significant results in suggesting, as they do. that the
daily consumption of green tea can prevent high blood pressure.
(#9) Y. Hara, T. Matsuzaki and T. Suzuki, Nippon Nogeikagaku Kaishi,
61,803(1987). 49~
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