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All living things inherit from their ancestors the genetic code that is on 4 kinds of DNA. DNA is an organic compound, which is similar to Inosinic acid, a "umami" component in bonito juice. A part of DNA composition can be changed when physical factors such as various chemicals, light, and ultraviolet are applied. When it is changed, the genetic code is changed, which is called mutation. Mutation effects living things greatly and living things are prepared themselves with anti-mutangenic matter. Changes and restoration of DNA are constantly occurring, and when the damage is large, it becomes difficult to be restored. Damages of DNA in cells can be a trigger to cause cancer and various diseases, one of which is senescence. DNA damage in germ cells affects descendant, causing hereditary disease. A few kinds of cancer diseases are hereditary, one of which is hereditary colon cancer. Therefore, anti-mutangenic effect is very significant for humans. The discovery by Dr. Tsuneo Kada 20 years ago that tea leaves extract and EGCG in catechins have anti-mutangenic effect, promoted the research of mutation, which made Japan a leader in the fields. Many researches on anti-mutangenic effect of green tea components are reported in 80's. You can refer to "Tea Science"131-144, and "Mutation Research, vol.436"69-97 for more details. Green tea catechins have three ways to control mutaion. Toripu‐P‐2 and Jinitropiren react directly to suppress the reaction of DNA and mutant. Green tea catechins derive detoxification, which promotes anti-tumor effect. In case of mutation by ultra-violet, catechins activate restoration process of living things against DNA damages, which promotes anti-tumor effect. When N-nitroamin is generated, green tea catechins react with nutric acids to control reactions with second rated amino acids. Vitamin C, which is contained in green tea, has similar effect and it is also an important stuff to control generation of carcinogen such as Nitrosoamin. Green tea catechins are also known that they reduce mutation by controlling generation of 8-OhdG that is produced by oxidation of DNA because they have strong effect on anti-oxidation and free radical. Timing of drinking tea is important as well as amount if those effects are to be maximized. People in Shizuoka prefecture drink tea before and during meals as well as after meals, which is reported to be very effective (Fig.1). Fig. 2 shows the differences of effects of different kinds of teas.

(Yoshiyuki Nakamura)