Japanese Green Tea History and Research
The Tea Museum was built in 1998 on the Makinohara upland* in Shizuoka prefecture, the leading tea-producing prefecture in Japan, this museum offers visitors a chance to taste local sencha green tea and to learn about the history of drinking and making tea in Japan and the processing of sencha tea leaves. Teas from all over the world, including black tea and oolong tea, are also displayed in the museum.
This upland with an average elevation of 90 m (35 ft) and an area of 50 sq km (20 sq mi) was brought under tea cultivation in the late 19th century and now produces about 40 percent of the total tea harvested in Shizuoka prefecture.
Sencha green tea is an everyday drink and made from the rolled form of tea
leaves.
The Japanese drink sencha tea when they want to relax or as a beverage to go
with a meal or snacks. It is also a Japanese custom to serve sencha tea to
visitors at the workplace or at home.
At formal sencha tea gatherings, different sencha teas are usually served with
sweets and a light meal.
There is another green tea, maccha, which is made from the powdered form of tea
leaves, and it is served mainly on ceremonial occasions.
Types of sencha tea
Sencha tea can be graded according to the quality of the tea leaves used into top-grade gyokuro tea, regular tea and bancha tea. Another popular type of tea is hojicha tea which is made from roasted tea leaves.
These types of sencha tea are all brewed the same way, by spooning them into tea pots, adding hot water and leaving them to steep.
Regular tea
Regular sencha tea has a light greenish-yellow tint and a good balance in flavor between pleasing astringency and sweetness.
(Supplement) Bancha tea, which is made from coarse tea leaves, has a more yellowish tint and a more astringent taste.
This is the most common tea. The tea leaves for regular sencha tea account for about 80 percent of all Japanese green tea including maccha tea leaves. The deeper the green of the leaves, the higher in grade.
Gyokuro tea
Gyokuro tea is strongest in both fragrance and flavor. A deep yellowish-green in tint, it is thick and smooth on the tongue and has a pleasing, slight astringency and sweetness.
It is made from the choicest, tenderest leaves, which are protected with blinds (usually made of straw) for a few weeks during the last stage of cultivation.
Hojicha (roasted) tea
Hojicha tea has a clear, light reddish-brown tint and a robust, roasted fragrance and flavor.
The leaves for hojicha tea are made by roasting regular sencha and bancha leaves until they turn brown. The roasting gives the tea a smoky fragrance and flavor.
The History of Research on Green Tea
In Asia, particularly in China, various effects of tea have been known since ancient times, but it was in the Western countries that effects of specific ingredients in tea were brought to light for the first time; tea caffeine was discovered in 1828 and tannin in 1848.
In Japan, studies on the ingredients in green tea began in the 1920s. As interest in their effects on health increased, extensive studies including animal experiments to investigate the physiological effects of green tea were begun in the 1980s.
These studies have revealed that green tea contains many beneficial substances for health, especially catechin, in addition to caffeine and vitamins A, C and E. Click here for the findings about the effects of the main ingredients.
Accumulated data implies that catechin in particular has effects on cancer, other adult (life and custom) diseases, virus-causes diseases, food poisoning, tooth decay, allergy, and so on.
Catechin, a kind of tannin, is the largest constituent (accounting for 10 to 20 percent) in green tea leaves. It dissolves into water, giving the tea astringency.
How effective is catechin?
Catechin is considered of particular medical value in the following areas.
Catechin is considered to possess the effects of:
preventing cancer;
The anti-cancer effect of catechin has been spotlighted most, so tests to scientifically verify the effect of catechin's preventing cancer are now in progress in the US as well as Japan.
Based upon results from animal studies and laboratory tests, catechin is considered to have the ability to inhibit the formation of carcinogenic* constituents and the increase and transfer of tumors**.
*a substance or agent producing or inciting cancer
**abnormal benign or malignant mass of tissue
Also surveys indicate a significant reduction in the death rate from cancer in tea-producing regions where residents are accustomed to drinking much green tea. One such survey is on the standardized mortality ratio (SMR), which shows that values for Shizuoka prefecture are remarkably lower than the national average.
preventing and improving conditions of other adult diseases;
Various adult diseases are spreading into younger generation these days due to changes in life styles and eating habits. Catechin is considered effective for:
-inhibiting the increase of cholesterol
Cholesterol is a fatty substance in tissue which is essential to health. However, the rise of cholesterol density above the normal level in blood could be a risky factor in arteriosclerosis*. Catechin is considered effective in inhibiting the absorption of excessive cholesterol and in balancing the level of cholesterol in the blood by maintaining HDL (high-density lipoprotein) and decreasing LDL (low-density lipoprotein)**.
*narrowing of the arteries because of fatty deposits, which can precipitate heart diseases, stroke and other cardiovascular diseases
**The HDL is considered to be a "good" cholesterol, helping remove cholesterol from tissues while LDL is a "bad" cholesterol, being a primary cause of heart attacks.
-inhibiting platelet agglutination*
*a reaction in which platelets collect into lumps
Platelets are disc-like structures in blood that help stop bleeding by forming plugs. On the other hand, cerebral and myocardinal infractions are triggered by agglutination. Catechin is considered effective for inhibiting excessive collection of platelets in blood.
-Improving high blood pressure conditions
High blood pressure is not only a serious condition by itself, but it is also the leading cause of heart attacks, strokes, and kidney failure.
The causes of high blood pressure are not yet fully understood, but it is clear that an enzyme (called renin), secreted by the kidney, causes the formation of a chemical substance (called angiotensin), which raises the blood pressure by causing the blood vessels to become narrower. Catechin is considered effective in inhibiting excessive activations of the enzyme and lowering the blood pressure accordingly.
-Improving diabetic conditions
Diabetes is a common but serious disease, leading to serious complications. It may cause changes in the blood vessels of the retina and the kidneys, and, in advanced stages, it becomes a major cause of blindness.
It is said that diabetes cannot be cured but proper treatment can improve a patient's condition considerably. The body of a diabetic person is slow to use sugar (glucose), and so sugar builds up in the blood, due mainly to a lack of the hormone insulin*, raising blood-sugar levels as a result.
*Insulin, which is produced by the pancreas, enables the body to use and store sugar quickly.
Catechin is considered effective in inhibiting sudden rises in blood-sugar levels. It is considered that catechin inhibits or delays the digestion and absorption of starches and sugars in the small intestine.
preventing food poisoning, tooth decay, and virus-causes diseases;
Catechin is said to prevent food poisoning caused by such bacteria as staphylococcuses, botulinuses and enteritis vibrios. Catechin has effects on germs, but it does not harm such beneficial bacteria for health as lactobacillus bifidus*, and, furthermore, it helps them increase, while it inhibits the increase of harmful bacteria, both in the same intestines.
*Lactobacillus bifidus breaks down sugars into lactic and other acids.
A platter of assorted sashimi* (yellowtail, seabream, flounder, tuna, and squid)
*Sashimi is fresh seafood fillets cut into bite-sized pieces, which are eaten raw with soy sauce.
Hot green tea is usually served with sashimi or sushi*, which can easily spoil. Is this a natural way of preventing food poisoning?
*vinegared rice topped or combined with sashimi and other items
Catechin is also said to have the ability to prevent dental decay* and plaque formation.
*Fluorine in green tea also plays a part too.
One special anti-virus effect of catechin is the prevention of influenza. Gargling with green tea is recommended by some doctors.
and alleviating allergies.
An allergy is a physical reaction that occurs in persons who are sensitive to certain substances*.
*These substances are called allergens. Not only house dust and pollen but also foods and such additives as preservatives are allergens.
Common forms of allergy include asthma, hey fever and sinus allergies. Others are itchy red swellings on the skin (eczema) and allergic headaches. The allergens, together with proteins called anti-bodies, act to release such substances as histamine from the body cells into the blood and other body fluids. These substances can cause allergic reactions.
Catechin is considered effective in inhibiting histamine from being released into the blood and other fluids, thus relieving the various allergic symptoms.
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