Botanical name: Camellia sinensis
Common name: Epigallocatechin Gallate (EGCG)
All teas (green, black, and oolong) are derived from the same plant, Camellia sinensis. The difference is in how
the plucked leaves are prepared. Green tea, unlike black and oolong tea,
is not fermented, so the active
constituents remain unaltered in the herb. The leaves of the tea plant are used both as a
social and a medicinal beverage.
The Japanese custom of drinking green tea came from China about 800 AD. The use of tea started when Buddhist monks, who had gone to China for study, returned to Japan bringing tea with them as a medicinal beverage. In the Kamakura era (1191-1333),the monk Eisai stressed the beneficial effects of tea in his book Maintaining Health by Drinking Tea (1211) : "Tea is a miraculous medicine for the maintenance of health. Tea has an extraordinary power to prolong life. Anywhere a person cultivates tea, long life will follow. In ancient and modern times, tea is the elixir that creates the mountain-dwelling immortal." From this passage we can see that green tea has from early times been highly valued as a powerful medication. But in recent years research into the effects of green tea has progressed so far it can now provide scientific confirmation for the legendary saying that "Tea is a miraculous medicine for the maintenance of health." It is becoming increasingly clear that green tea has a broad efficacy in preventing disease. The remainder of this brochure will introduce you to the main points of the research summarized in the "The Components and Healthy Effects of Green Tea.,(Table1)(#1) (#1) I.Oguni and Y. Hara,"Green tea has many medicinal activities for preventing disease such as cancer, cardio-vascular diseases and diabetes". (published by The Chunichi-shinbun, Nagoya, Japan),PP.1-289 (1990). |
Discussions of food normally were focussed on its nutritional content and its flavor. Recently, however, more
attention is being paid to the role of food in bio-regulating functions. Foods that possess this regulatory
function are called "functional food." Dr. Inaba(#20) classifies food by function as shown in Table 9. If we classify green tea and green tea
catechin according to this table, they possess the following functions : (1) bio-defensing function by preventing
cancer through fortification of the immune system, (2) disease-preventing function by preventing high blood pressure
or diabetes, (3) disease-recovery function by inhibiting the rise of cholesterol, (4) physical rhythm-controlling
function by stimulating the central nervous system with caffeine and (5) aging-suppressing function by providing
the body with antioxidants. Green tea is, therefore, rich in possibilities as a functional food and should
prove a popular beverage among the new health conscious generation. (#2O) H. Inaba.Food Chemicals. 4 (No. 11,) 32 (1988) |
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 under 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 the constriction of the blood vessels
caused by this constrictor that leads to high blood pressure. (#9) Y. Hara, T. Matsuzaki and T. Suzuki, Nippon Nogeikagaku Kaishi, 61,803(1987). 49~ |
Green tea deters food poisoning. It has long been known from experience that green tea has the ability
to kill bacteria. Consumption of strong green tea, for example, is often recommended as a good treatment for
diarrhea. (#13) Y. Hara and T. Ishigami, Nippon Shokuhin Kogyo Gakkaishi, 36, 996 (1989). (#14) T. Shimamura et al.. Jpn. f.Bacteriol., 44, 669 (1989). |
Dr. Okada(#17) has noted the fact that tobacco growers use an exudat of green tea to prevent crop damage by
the tobacco mosaic virus an verified that green tea catechin suppresses the growth of this virus. In addition,
Prof. Shimamura(#18) has determined that green tea catechin and the aflavin (an oxidized form of catechin) present
in black tea have a strong effect on the influenza virus. Green tea catechin and black tea the aflavi directly
act on the influenza virus and inactivate it. It appears, therefore, that gargling with green or black tea
is very effective in preventing influenza. This effect is increased by keeping the green tea catechin and the
virus in contact as long as possible. (#17) F. Okada, Chagyo Kenkyu Hokoku, 48, 52 (1978). |
About 60 years ago, Dr. Minowada of Kyoto University noticed that sugar in the urine of patients hospitalized
for diabetes fell markedly during periods when they participated in chanoyu (Tea Ceremony). He reported that
powdered tea of the type used in the traditional Tea Ceremony had the capability of lowering blood sugar. Unfortunately,
however, this important report was ignored due to the outbreak of World War II and the subsequent postwar food
shortages. But the arrival of the gourmet era in recent years in Japan has led to heightened interest in diabetes
and the ability of green tea to reduce blood sugar. (#10) H. Asai, Y. Kuno, H. Ogawa, Y. Hara and K. Nakamura, Kiso to Rinsshyo, 21, 163 (1987). |
Cancer mortality statistics on Japanese people indicate that the death rate from cancer is significantly lower,
for both men and women, i Shizuoka Prefecture. This fact stimulated our interest in cancer prevention and led us
to calculate the death rate (Standardized Mortality Ratio) b cancer type for every city, town and village in Shizuoka
Prefecture. Based on these death ratio statistics, we created a cancer distribution map of the Prefecture and examined
it in detail for trends. We found that areas devoted to green tea production in the central and western regions
of Shizuoka Prefecture exhibit a significantly lower death rate for all types of cancer in general and for gastrointestinal
cancers such as stomach, esophagus and liver cancer in particular.(#2)We then made a survey to see how the
residents of the green tea producing regions, which have such low cancer death rates, drink their tea. The results
showed that those who live in areas where green tea is the staple crop tend to drink it daily in rather strong
concentrations by frequently refreshing the tea leaves in their pots.(#2,3) From these results we theorized that
green tea must be connected in some way with cancer prevention, and we decided to continue our research with animal
experiments. (#2)I.Oguni et al., Japanese J. of Nutrition, 47, 31 (1989). |
Oxygen is necessary for human life. But oxygen has two aspects, one beneficial and one malign.
The oxygen we breathe is conveyed to every part of the body where it plays a key role in metabolism. But it can
also be a very harmful agent in the form of active or free radical oxygen. Active oxygen is a problem because it
can combine with anything in the body and oxidize it with consequent destruction of cell membranes, damage to DNA
and oxidation of lipids (fats). All of these can lead to diseases like cancer. Here we shall focus on the
process by which active oxygen combines with lipids (fats) in the body to create lipid peroxide, that is, lipid
with an excessive amount of oxygen. (#12)T.OKUDAet al.,Chem.Pharm.Bull.,31,1625(1983). |
Dental techniques have improved greatly in the past few years, but once teeth have been damaged by cavities
they can never be restored to their original condition. It is of the highest priority, therefore, to prevent cavities
from developing in the first place. By the end of the 19th century, it had been determined that cartes are caused
by cariogenic bacteria. The cariogenic bacteria first produce non-watersoluble glucan from sugar or other foods,
and this glucan adheres to the tooth enamel as hard plaque. Next, they feed on sugar to generate acids such as
lactic acid in the plaque. These acids then dissolve the tooth enamel. That in brief is the mechanism of cavity
production. (#15) M. Hattori et al., Chem. Pharm.. Bull., 38, 717 (1990). |
Cholesterol is always indicted as the "bad guy for causing a wide range of diseases in adults. But it
is a chemical present in all animals and crucial in human bodies for such important processes as the manufacture
of cell membranes and the adhesion of cells. There are two types of cholesterol: one is the so-called bad cholesterol
(LDL and VLDL- cholesterol) that accumulates in tissues and the other is the "good, cholesterol (HDL-cholesterol)
that collects excessive cholesterol from the tissues. If the amount of bad cholesterol in the blood increases
too much, it is deposited on the walls of blood vessels and can lead to atherosclerosis. Atherosclerosis in conjunction
with high blood pressure can cause myocardial infarction and cerebral infarction. Good cholesterol, however,
prevents atherosclerosis and must exist in a proper balance with bad cholesterol for proper health. (#7) K. Muramatsu and Y. Hara, J. Nutr. Sci. Vitaminol, 32, 613 (1986). (#8) K. Goto, S. Kanaya and Y. Hara, Proc. of the International Symp. on Tea Science, 314 (Shizuoka, Japan;August,1991) |
Tea contains caffeine which, when taken in the proper quantity, simulates every organ in the body. It
has a particularly strong effect on the central nervous system, heart and liver. This reaction is even more
pronounced when one is sleepy or tired. A cup of tea or coffee will help clear a dull mind after rising in the
morning or after a prolonged period without sleep. The power to stimulate and awaken the mind comes from caffeine.
It is also said that the amount of caffeine contained in normal servings of green tea can stimulate the skeletal
muscles and facilitate muscular contraction. For this reason, it is quite helpful to drink tea or coffee in the
middle of work to refresh the mind and restore the body. We find it noteworthy that there is some scientific support
for such old customs as the afternoon snack, coffee break or tea time ritual. |
Although the origin of tea in Japan is not clear, it is said that in the Nara/Heian era the custom of drinking tea was brought by monks from China, who also brought seeds of tea trees. As for the origin of tea trees, it is also said that there were native tea trees in Japan. Among old documents, tea was mentioned in Kigodokkyou, Kansoujirui and Koujikongen in the early Nara era. However, it is not clear whether the tea was produced in Japan or brought from China. There is a Chinese poem in Kyoukokushuu which support the hypothesis that we had native tea trees in Japan. A court lady of the Saga Emperor wrote: "she boiled the spring water and made some tea. The tea with a little bit of salt tasted better." Also there is a poem saying that the Taijou Emperor had tea with the monk Kaikou, seeing Kuukai off when he went back to the mountain. From these we can guess that the custom of drinking tea had spread among the upper-class at that time. Many poems written about tea can be found in Ryouunshuu and Bunka Syuureisyuu, written in the same era as Kyoukokushuu. In Hiyoshiyashiro shintou himituki it is stated that Saichou planted the tea seeds he brought from China in the area of Hiyoshiyashiro. However, Kokon Yourankou-no-Kusakibu, Cha-no-Seigo, edited by Yashiro Hirotaka and others in the Edo period, quotes as follows; "The book seems to be written by Maeda Kain. Since the book was written much later than the era of Denkyou Daishi, there is no evidence to prove that Denkyou Daishi planted tea in this country and did so in Uji, Toganoo. Thus, we conclude that the story is not fact. Also, according to Nihon Chagyou Hattatusi by Ooishi Sadao, the tea tree in Hiyoshi was investigated and found not to be of Chinese origin. Does this mean that someone later planted a new tea tree after the original one died? Further, in Kokon Yourankou it is stated "we do not find any literature saying that Senkou Kokushi (Eizai) and Myoukei Syounin loved drinking tea, thus, we should conclude that the origin of tea in Japan mentioned in Nihon Kouki begins with the tea brought from China in Kounin-nen which was given to Nanto Gomyouhoushitei by the monk Eichyu of Soufukuji in Oumi country. |
Exerpt from Cha-no-Daijiten
by Yuusuke Kubokawa and Keiichi Fukushima
Lowers total cholesterol and LDL (bad)-cholesterol levels
Increases HDL (good)-cholesterol levels
Reduces blood pressure
Lowers blood sugar
Acts as "blood thinner"
Reduces the risk of cancer
Reduces the risk of heart attack
Decreases the risk of stroke
Decrease the risk of developing rheumatoid arthritis
Protects against Parkinson's disease
Enhances immune function
Acts as an antibacterial and antiviral agent
Helps burn extra calories
Prevents dental cavities and gum disease
Builds stronger bones
Boosts longevity
Botanical name: Camellia sinensis
Common name: Epigallocatechin Gallate (EGCG)
All teas (green, black, and oolong) are derived from the same plant, Camellia sinensis. The difference is in how
the plucked leaves are prepared. Green tea, unlike black and oolong tea, is not fermented,
so the active
constituents remain unaltered in the herb. The leaves of the tea plant are used both as a social and a medicinal
beverage.
Green tea has been used in connection with the following conditions
Rating Health Concerns
Atherosclerosis
Colon cancer (reduces risk)
High cholesterol
Leukoplakia
Tooth decay
Weight loss
Breast cancer (risk reduction)
Crohn’s disease
Hemochromatosis (iron overload)
High triglycerides
Hives
Immune function
Infection
Lung cancer (risk reduction)
Reliable and relatively consistent scientific data showing a substantial health benefit.
Contradictory, insufficient, or preliminary studies suggesting a health benefit or minimal health benefit.
An herb is primarily supported by traditional use, or the herb or supplement has little scientific
support and/or minimal health benefit.
Historical or traditional use (may or may not be supported by scientific studies)
According to Chinese legend, tea was discovered accidentally by an emperor 4,000 years ago.
Since then, Traditional Chinese Medicine has recommended green tea for headaches,
body aches and pains, digestion, depression, immune enhancement, detoxification,
as an energizer, and to prolong life.
Active constituents
Green tea contains volatile oils, vitamins, minerals, and caffeine, but the primary constituents
of interest are the polyphenols, particularly the catechin called epigallocatechin gallate
(EGCG). The polyphenols are believed to be responsible for most of green tea’s roles
in promoting good health.1
Green tea has been shown to mildly lower total cholesterol levels and improve the cholesterol
profile
(decreasing LDL “bad” cholesterol and increasing HDL “good” cholesterol) in most,2 3 4 5 but not
all,6 studies. Green tea may also promote cardiovascular health by making platelets in the
blood less sticky.
Green tea has also been shown to protect against damage to LDL (“bad”) cholesterol caused
by
oxygen.7 Consumption of green tea increases antioxidant activity in the blood.8 Oxidative damage to
LDL can promote atherosclerosis. While population studies have suggested that consumption of
green tea is associated with protection against atherosclerosis,9 the evidence is still preliminary.
Several animal and test tube studies have demonstrated an anticancer effect of polyphenols from
green tea.10 11 12 In one of these studies, a polyphenol called catechin from green tea effectively
inhibited metastasis (uncontrolled spread) of melanoma (skin cancer) cells.13 The polyphenols in
green tea have also been associated with reduced risk of several types of cancer in humans.14 15 16
However, some human studies have found no association between green tea consumption and
decreased cancer risk.17 18
In a double-blind trial, people with leukoplakia (a pre-cancerous oral condition) took 3 grams orally
per day of a mixture of whole green tea, green tea polyphenols, and green tea pigments orally, and also
painted a mixture of the tea on their lesions three times daily for six months.19 As compared to the
placebo group, those in the green tea group had significant decreases in the pre-cancerous condition.
Compounds in green tea, as well as black tea, may reduce the risk of dental caries.20
Human
volunteers rinsing with an alcohol extract of oolong tea leaves before bed each night for four
days had significantly less plaque formation, but similar amounts of plaque-causing bacteria,
compared to those with no treatment.21
Green tea polyphenols have been shown to stimulate the production of several immune system
cells,
and have topical antibacterial properties—even against the bacteria that cause dental plaque.22 23 24
One study found that intake of 10 cups or more of green tea per day improved blood test results,
indicating protection against liver damage.25 Further studies are needed to determine if
taking green tea helps those with liver diseases.
Tea flavonoids given by capsule reduced fecal odor and favorably altered the gut bacteria in elderly
Japanese with feeding tubes living in nursing homes.26 The study was repeated in bedridden elderly
not on feeding tubes, and green tea was again shown to improve their gut bacteria.27 These studies
raise the possibility of using green tea in other settings where gut bacteria are disturbed, such as
after taking antibiotics. Further studies are needed to clarify the role of green tea in this respect, however.
High-tannin tea has been shown to reduce the need for blood removal from people with iron overload,
or hemochromatosis, in an open study.28 The tea had to be taken with meals and without lemon or milk
to be effective. Tea is believed to help in hemochromatosis by preventing iron absorption.
How much is usually taken?
Much of the research documenting the health benefits of green tea is based on the amount
of green tea
typically consumed in Asian countries—about 3 cups (750 ml) per day (providing 240–320 mg of polyphenols).29
However, other research suggests as much as 10 cups (2,500 ml) per day is necessary to obtain noticeable
benefits from green tea ingestion.30 31 To brew green tea, 1 teaspoon (5 grams) of green tea leaves are
combined with 1 cup (250 ml) of boiling water and steeped for three minutes. Decaffeinated tea is recommended
to reduce the side effects associated with caffeine, including anxiety and insomnia. Tablets and capsules
containing standardized extracts of polyphenols, particularly EGCG, are available. Some provide up
to 97% polyphenol content—which is equivalent to drinking 4 cups (1,000 ml) of tea. Many of these
standardized products are decaffeinated.
Are there any side effects or interactions?
Green tea is generally free of side effects. The most common adverse effects reported
from consuming
large amounts (several cups per day) of green tea are insomnia, anxiety, and other symptoms caused
by the caffeine content in the herb.
An extract of green tea taken by healthy women with a meal inhibited the absorption of non-heme iron
(e.g., the form of iron in plant foods) by 26%.32 Frequent use of green tea could, in theory, promote the
development of iron deficiency in susceptible individuals.
Are there any drug interactions?
Certain medicines may interact with green tea. Refer to drug interactions for a list of those medicines.
References
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