Matcha

 

 

Written by Dr.Itaro OGUNI

Professor of Food Science

Department of Food and Nutritional Sciences

University of Shizuoka,Hamamatsu College

Green tea acts as a function food

Discussions of food normally were focussed on its nutritional conten 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 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 roviding the body with antioxidants. Green tea is, therefore, rich in ossibilities as a functional food and should prove a popular beverage mong the new health conscious generation.

Green tea, with its sweet aroma and eternally fresh taste, has been oved and continuously drunk since its introduction to Japan centuries ago. But modern research has finally started to remove the veil concealing some of its true power as a functional food. Green tea is truly a "miraculous medicine with an extraordinary power to prolong life.

H. Inaba.Food Chemicals. 4 (No. 11,) 32 (1988)

 

Green tea Prevents cancer

Cancer mortality statistics on Japanese people indicate that th death rate from cancer is significantly lower, for both men and women, i Shizuoka Prefecture.

This fact stimulated our interest in cancer preventio 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.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. 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.

Mice were first inoculated with cancer cells and then studied for the growth of malignancies. One group was given an extract of green tea while another control group was not given such an extract. Comparison of the two groups showed a marked reduction in the growth of tumors among the receiving green tea .In further joint research with Prof. Shu-Jun Cheng of the Cancer Institute, Chinese Academy of Medical Science (Beijing),mice were given substances which, when transformed in the body to cancer-causing chemicals, generate carcinoma in both the esophagus and forestomach. The researchers then proceeded to check if green tea has the ability to inhibit the development of these cancers. Administration of green tea extract did indeed reduce the incidence of cancer to less than 50%. In addition, research at the National Cancer Institute (Tsukiji, Tokyo) has demonstrated that administration of catechin (the main component of green tea tannin) to mice previously given chemicals that induce duodinal cancer can also significantly lower the incidence of cancer. Green tea and its component catechin have, therefore, been shown to reduce the growth as well as the actual generation of cancer.

From our prevlous epldemiologlcal research we can estlmate that the inhabitants of the midwestern region of Shizuoka Prefecture, where green tea is the staple product and the main beverage, consume as much as 1.0 1.sg of crude green tea catechins daily in their green tea. This strongly suggests that green tea catechin plays a role in their low SMR (Standardized Mortality Ratio) for stomach cancer.

We do not yet fully understand the mechanism underlying the generation of cancer, but it involves at least the following two stages. This is called the "two-stage theory of cancer development., A substance capable of causing mutations (initiator) first damages DNA in the cell and renders it subject to cancer (initiation). This condition then remains unchanged for some time until another substance, which activates cancer (promoter),leads to the actual growth of a malignancy (promotion). It is clear from recent research that extract of green tea and catechin can markedly inhibit both stages of development.

Even though these results have been gained from animal studies or pure laboratory tests, we think it highly significant that green tea and its component catechin have the ability to prevent cancer. When taken together with the survey that indicates a striking reduction in the cancer death rate in the tea producing regions where the residents are accustomed to drinking quite strong tea by frequent changes of tea leaves, they support the conclusion that green tea may also be a factor in the prevention of human cancer.

I.Oguni et al., Japanese J. of Nutrition, 47, 31 (1989).

I.Oguni, Metabolzsm and Disease, 29, 453, (1992).

I.Oguni et al.Biol.Chem,52,1879(1988)

I.Oguni and ShuJun Cheng,Annual Report of the Skylark Food Science

Institute,No 3,57(1991)

Y.NAKAMURA etal,PROC.ofInternatiomal Tea-Quality-Human Health

Symposium,pp.227-238(Hangzhou,china,November,1987)

 

Green tea restricts the increase of blood cholesterol

Cholesterol is always indicted as the "bad guyn 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.

Prof. Muramatsu, has demonstrated in experiments with rats that green tea catechin restricts the excessive buildup of blood cholesterol. When rats were fed a diet high in fat, the amount of bad cholesterol in the blood increased rapidly. But the addition of only 1% catechin to the food checked the increase of bad cholesterol (LDL) with only minimal effect on the amount of good cholesterol (HDL). In another series of experiments, rats fed normal food with catechin exhibited no decrease in blood cholesterol and remained unaffected by the supplement. We can see from these results that green tea catechin acts to limit the excessive rise in blood cholesterol. Recently Dr. Goto reported similar results for human blood cholesterol.

K. Muramatsu and Y. Hara, J. Nutr. Sci. Vitaminol, 32, 613 (1986).

K. Goto, S. Kanaya and Y. Hara, Proc. of the International Symp. on Tea Science, 314 (Shizuoka, Japan;August,1991)

 

Green tea controls high blood pressure

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 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.Green tea controls high blood pressure

Y. Hara, T. Matsuzaki and T. Suzuki, Nippon Nogeikagaku Kaishi, 61,803(1987). 49~

 

Green tea lowers the blood sugar level

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.

The sugars and carbohydrate in our food are digested mainly in the duodenum, converted there to glucose and then absorbed into the blood. The agent that regulates the intake of blood sugar into the tissues is insulin, a chemical secreted from Langerhans islets on the pancreas. Diabetes is a disease characterized by insufficient secretion or improper functioning of insulin, which hinders the proper absorption of glucose into the tissues and leads to a high concentration of blood sugar that must eventually be excreted into the urine. If this high concentration of blood sugar should continue for a long period, it will affect the vascular system and cause a number of quite serious diseases including atherosclerosis and retinal hemorrhages. Dr. Hara gave dried green tea catechin in edible form to mice that were subject to hereditary diabetes and verified a lowering of their blood sugar. In parallel experiments, Dr. Shimizu gave an extract of green tea to mice and demonstrated that it had the ability to lower blood sugar. It has also been shown that the polysaccharides in green tea possess the same ability. Although these results come from animal tests, the evidence that green tea catechin and polysaccharides can lower blood sugar In mice may also, in light of Dr. Minowada's old report, apply to humans.

(#10) H. Asai, Y. Kuno, H. Ogawa, Y. Hara and K. Nakamura, Kiso to Rinsshyo, 21, 163 (1987).

 

Green tea suppresses aging

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 consequentdestruction of cell membranes, damageto 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. Lipid peroxide is thought to be a harmful substance which can trigger the diseases such as cancer, cardio-vascular disease and diabetes. Since lipid peroxide is more easily generated and less easily purged as age advances, it tends to accumulate in the body. Lipofuscin, called the *aging pigment,, also accumulates in the body in proportion to age and is considered to be an index of aging. But lipofuscin is itself created by lipid peroxide, which suggests a connection between aging and lipid peroxide. One way to slow aging may, therefore, be to prevent the production and accumulation of active oxygen and lipid peroxide in the body. It has been shown, for example, that the higher the concentration of the powerful antioxidants vitamins E and C in the bodies of animals, the longer they live. This suggests that active consumption of agents that are effective antioxidants will restrain the aging process. We already know that green tea is rich in those vitamins that possess this antioxidizing capability. In addition, Prof. Okuda has recently demonstrated that catechin in green tea is a far stronger antioxidant than vitamin E (about 20 times stronger in fact). These results come from laboratory tests only, and we must wait for further research to confirm a direct cause and effect relationship between the antioxidizing function of green tea and the retardation of aging. But the very fact that green tea contains a powerful antioxidant is a strong foundation for believing it can help control aging.

T.OKUDAet al.,Chem.Pharm.Bull.,31,1625(1983).

 

Green tea deters food poisoning

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.

Dr. Hara has shown in his research that catechin is a powerful sterilizing agent for many types of bacteria that cause food poisoning (Table 5). He checked the Minimum Inhibitory Concentration (MIC, ppm) of green tea catechin necessary to stop the growth of various types of food poisoning bacteria and found that (a) Staphylococcus aureus, (b) Vibrio parahaemolyticus, (c) Clostridium peifringens, (d)Bacillus cereus, (e) Plesiomonas shigelloides, (f) Aeromonas sobria and (g)Clostridium botulinum cannot grow in the 1/10 1/2 of 0.1% of catechin in the green tea normally drunk by the Japanese people. But even fairly high concentrations of catechin had no negative effect on the bifidtcs bacillus, which is necessary ~ for proper functioning of the intestinal tract. In addition to this evidence, Prof. Shimamura has reported that green tea is a very strong sterilant of cholera vibrio and has a strong antitoxic effect on toxins produced by bacteria other than cholera.

These results indicate the antibacterial function of green tea catechin and suggest that it may be effective in preventing food poisoning. Every year throughout the world there are countless incidents of food poisoning.

Y. Hara and T. Ishigami, Nippon Shokuhin Kogyo Gakkaishi, 36, 996 (1989).

T. Shimamura et al.. Jpn. f.Bacteriol., 44, 669 (1989).

 

Green tea stops cavlties

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. To prevent cavities it is necessary, then, to keep plaque off the teeth by hrushing an important tool in good dental hygiene. But according to experiments by Dr. Hattori(#15) green tea catechin can suppress the process (glucosyl transferase) by which cariogenic bacteria create glucan (Table 6).Other experiments by Dr. Sakanaka(#16) have verified that green tea catechin can destroy cariogenic bacteria (Table 7). That is, it is antibacterial. Clearly, then, green tea catechin not only suppresses the formation of plaque by cariogenic bacteria but also kills the bacteria themselves.

It has been known for some time that small amounts of fluorine can strengthen teeth and help prevent cavities. For this reason, many cities add fluorine to their drinking water. Green tea, however, contains natural fluorine and is thought to help prevent cavities. That may explain those reports that show a reduction in cavities among grade school children who drank green tea after lunch.

Halitosis or bad breath embarrasses many people. It is caused by a number of bacteria that flourish in the mouth. Green tea can also kill other oral bacteria besides those causing cartes. It has, therefore, some ability to prevent bad breath by destroying the cause of bad breath. Why not enjoy gleaming white teeth and a fresh breath by drinking green tea?

M. Hattori et al., Chem. Pharm.. Bull., 38, 717 (1990).

S. Sakanaka et al.. Agric. Biol. Chem., 53, 2307 (1989).

 

Green tea fights virus

Dr. Okada 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. I addition, Prof. Shimamura has determined that green tea catechin and theaflavin (an oxidized form of catechin) present in black tea have a stron effect on the influenza virus. Green tea catechin and black tea theaflavi 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. It is also hoped that the antiviral capability of green tea catechin may have some beneficial effect on the AIDS (Acquired Immune Deficiency Syndrome) virus, which is now the world's most feared infectious disease. Dr. Nakane and Dr. Ono at the Aichi Cancer Institute have verified the fact that green tea catechin can inhibit the activity of the AIDS virus in laboratory test. Although this research is just in its nascent stage, it provides a slight ray of hope that a treatment may someday be found to combat the now unstoppable AIDS virus. Future research advances in this field are expected.

F. Okada, Chagyo Kenkyu Hokoku, 48, 52 (1978).

T. Shimamura et al., Lett. APPI. Microbiol., 11, 38 (1990).

H. Nakane and K. Ono, Biochemistry, 29, 2041 (1990).