|
The beverage
green tea (Simplified
Chinese: Traditional Chinese:
Pinyin:
lǜchá) is a "true"
tea (i.e., Camellia sinensis)
that has undergone minimal
oxidation during processing.
Green tea is
popular in China, Korea,
Uzbekistan, Kyrgyzstan,
Kazakhstan, Japan, Pakistan,
Taiwan, Hong Kong, Morocco, and
the Middle East. Recently, it
has become more widespread in
the West, where traditionally
black tea is consumed.
History
There is archaeological
evidence that suggests that tea
has been consumed for almost
5000 years, with India and China
being two of the first countries
to cultivate it. Green tea has
been used as traditional
medicine in areas such as India,
China, Japan and Thailand to
help everything from controlling
bleeding and helping heal wounds
to regulating body temperature,
blood sugar and promoting
digestion.
The Kissa Yojoki (Book
of Tea, written by Zen
priest Eisai in 1191, describes
how drinking green tea can have
a positive effect on the five
vital organs, especially the
heart. The book discusses tea's
medicinal qualities, which
include easing the effects of
alcohol, acting as a stimulant,
curing blotchiness, quenching
thirst, eliminating indigestion,
curing beriberi disease,
preventing fatigue, and
improving urinary and brain
function. Part One also explains
the shapes of tea plants, tea
flowers, and tea leaves, and
covers how to grow tea plants
and process tea leaves. In Part
Two, the book discusses the
specific dosage and method
required for individual physical
ailments.
United States Food and Drug
Administration (FDA)
The article Tea: A Story
of Serendipity appeared in
the March 1996 issue of FDA
Consumer Magazine and looked at
the potential benefits of green
tea. At that time they had not
done any reviews of the
potential benefits of green tea
and were waiting to do it until
health claims were filed. They
have since denied two petitions
to make qualified health claims
as to the health benefits of
green tea.
On June 30, 2005, in response
to "Green Tea and Reduced Risk
of Cancer Health Claim", they
stated: "FDA concludes that
there is no credible evidence to
support qualified health claims
for green tea consumption and a
reduced risk of gastric, lung,
colon/rectal, esophageal,
pancreatic, ovarian, and
combined cancers. Thus, FDA is
denying these claims. However,
FDA concludes that there is very
limited credible evidence for
qualified health claims
specifically for green tea and
breast cancer and for green tea
and prostate cancer, provided
that the qualified claims are
appropriately worded so as to
not mislead consumers."
On May 9, 2006, in response
to "Green Tea and Reduced Risk
of Cardiovascular Disease", they
concluded "there is no credible
evidence to support qualified
health claims for green tea or
green tea extract and a
reduction of a number of risk
factors associated with CVD."
However in October 2006, the
FDA approved an ointment based
on green tea. New Drug
Application (NDA) number
N021902, for kunecatechins
ointment 15% (proprietary name
Veregen) was approved on October
31, 2006, and added to the
"Prescription Drug Product List"
in October 2006. Kunecatechins
ointment is indicated for the
topical treatment of external
genital and perianal warts.
Scientific studies
A 2006 study published in the
September 13 issue of the
Journal of the American Medical
Association concluded "Green tea
consumption is associated with
reduced mortality due to all
causes and due to cardiovascular
disease but not with reduced
mortality due to cancer." The
study, conducted by the Tohoku
University School of Public
Policy in Japan, followed 40,530
Japanese adults, ages 40-79,
with no history of stroke,
coronary heart disease, or
cancer at baseline beginning in
1994. The study followed all
participants for up to 11 years
for death from all causes and
for up to 7 years for death from
a specific cause. Participants
who consumed 5 or more cups of
tea per day had a 16 percent
lower risk of all-cause
mortality and a 26 percent lower
risk of cardiovascular disease
than participants who consumed
less than one cup of tea per
day. The study also states, "If
green tea does protect humans
against CVD or cancer, it is
expected that consumption of
this beverage would
substantially contribute to the
prolonging of life expectancy,
given that CVD and cancer are
the two leading causes of death
worldwide."
A study published in the
February 2006 edition of the
American Journal of Clinical
Nutrition concluded "A higher
consumption of green tea is
associated with a lower
prevalence of cognitive
impairment in humans."
In May 2006, researchers at
Yale University School of
Medicine weighed in on the issue
with a review article that
looked at more than 100 studies
on the health benefits of green
tea. They pointed to what they
called an "Asian paradox," which
refers to lower rates of heart
disease and cancer in Asia
despite high rates of cigarette
smoking. They theorized that the
1.2 liters of green tea that is
consumed by many Asians each day
provides high levels of
polyphenols and other
antioxidants. These compounds
may work in several ways to
improve cardiovascular health,
including preventing blood
platelets from sticking together
(This anticoagulant effect is
the reason doctors warn surgical
patients to avoid green tea
prior to procedures that rely on
a patient's clotting ability)
and improving cholesterol
levels, said the researchers,
whose study appeared in the May
issue of the Journal of the
American College of Surgeons.
Specifically, green tea may
prevent the oxidation of LDL
cholesterol (the "bad" type),
which, in turn, can reduce the
buildup of plaque in arteries,
the researchers wrote.
A study published in the
August 22, 2006 edition of
Biological Psychology looked at
the modification of the stress
response via L-Theanine, a
chemical found in green tea. It
"suggested that the oral intake
of L-Theanine could cause
anti-stress effects via the
inhibition of cortical neuron
excitation."
In a double-blind,
randomized, placebo-controlled
trial done by Division of
Cardiovascular Medicine,
Vanderbilt University Medical
Center, Nashville, Tennessee,
240 adults were given either
theaflavin-enriched green tea
extract in form of 375mg capsule
daily or a placebo. After 12
weeks, patients in the tea
extract group had significantly
less low-density lipoprotein
cholesterol (LDL-C) and total
cholesterol (16.4% and 11.3%
lower than baseline, p<0.01)
than the placebo group. The
author concluded that theaflavin-enriched
green tea extract can be used
together with other dietary
approaches to reduce LDL-C.
A study published in the
January, 2005 edition of the
American Journal of Clinical
Nutrition concluded "Daily
consumption of tea containing
690 mg catechins for 12 wk
reduced body fat, which suggests
that the ingestion of catechins
might be useful in the
prevention and improvement of
lifestyle-related diseases,
mainly obesity."
Antioxidants in green tea may
prevent and reduce the severity
of rheumatoid arthritis,
according to a Case Western
Reserve University School of
Medicine study published in the
April 13 2005 issue of the
Proceedings of the National
Academy of Sciences. The study
examined the effects of green
tea polyphenols on
collagen-induced arthritis in
mice, which is similar to
rheumatoid arthritis in humans.
In each of three different study
groups, the mice given the green
tea polyphenols were
significantly less likely to
develop arthritis. Of the 18
mice that received the green
tea, only eight (44 percent)
developed arthritis. Among the
18 mice that did not receive the
green tea, all but one (94
percent) developed arthritis. In
addition, researchers noted that
the eight arthritic mice that
received the green tea
polyphenols developed less
severe forms of arthritis.
A German study found that an
extract of green tea and hot
water (filtered), applied
externally to the skin for 10
minutes, three times a day could
help people with skin damaged
from radiation therapy (after
16-22 days).
A study published in the
December 1999 American Journal
of Clinical Nutrition found that
"Green tea has thermogenic
properties and promotes fat
oxidation beyond that explained
by its caffeine content per se.
The green tea extract may play a
role in the control of body
composition via sympathetic
activation of thermogenesis, fat
oxidation, or both."
In lab tests, EGCG, found in
green tea, was found to prevent
HIV from attacking T-Cells.
However, it is not known if this
has any effect on humans yet.
A study in the August, 2003
issue of a new potential
application of Cellular and
Molecular Life Sciences found
that "a new potential
application of
(–)-epigallocatechin-3-gallate
[a component of green tea] in
prevention or treatment of
inflammatory processes is
suggested"
|