Considerable research is being carried out on the role of tea
drinking in preventing cancer. Out of twenty-five papers related to
health presented at the best results, with Lung Ching preferred.
Stomach cancer, the number one cause of death in Japan, is at its
lowest rate in Shizuoka prefecture along the coast southwest of
Tokyo. One explanation is that Shizuoka is a tea-growing district
and its inhabitants drink large amounts of green tea. This is the
conclusion of Professor I. Oguni of Shizuoka University, who did a
twelve-year study using government demographic figures.
The study polled people in cities with high and low mortality rates from
gastric cancer. In the low mortality areas, it found that people
drank tea often and drank it strong. In the high mortality spots
they favored weak tea and drank it infrequently, according to
research presented by Oguni and others from Hamamatsu College of
Shizuoka University and Terumo Corporation, at the Hang Zhou
Symposium.
Similar findings were reported from a survey in China's Sichuan
province in 1986 and another in 1986-1989 in Jiangsu province. The
incidence of stomach cancer was found to be remarkably lower in
Sichuan areas of heavy tea drinking. Jucha county in Jiangsu, where
mush tea is drunk, was found to have a lower incidence of liver
cancer than Qidong county, where not so much tea is used.
Tea
has some effect against cancer because it inhibits the formation or
action of cancer-causing substances. Tea may block the action of
nitrosamines which can cause cancer, said Dr. Han Chi, an associate
professor at the Institute of Nutrition and Food Hygiene under the
Chinese Academy of Preventative Medicine. In a test of 145 types of
tea, she and her colleagues rated green tea highest, with a blocking
rate of 90%. Brick, Jasmine, oolong, and black tea followed in that
order. They found that one gram of tea had some effect, and that
three to five grams (three grams is one teaspoon) completely blacked
the synthesis of nitrosamines in the human body. But it is too early
to draw any conclusions, Dr Han told the Beijing meeting.
Other research at Hamamatsu College found that green tea inhibits
the action of MNNG (N-methyl-N1-nitro-N-nitrosoguanidine), a
synthetic carcinogen. This substance decreased by 84 percent in the
blood of mice drinking green tea and 82% with black tea. On mice fed
Japanese green tea, induced malignant tumors did not develop as
rapidly as in those not on tea, according to Oguni and other
researchers at Shizuoka University's School of Pharmaceutical
Science and the Hamamatsu College Department of Food Nutrition.
Green tea also inhibits the action of aflatoxin, a powerful
carcinogen produced by mold in stored crops such as grains and
peanuts. This ability of tea to counteract this chemical has been
demonstrated in several Chinese studies.
