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"Better to be deprived of food for three days, than tea for one." (Ancient Chinese Proverb)
Is any other food or drink reported to have as many health benefits as green tea? The Chinese have known about the medicinal benefits of green tea since ancient times, using it to treat everything from headaches to depression. In her book Green Tea: The Natural Secret for a Healthier Life, Nadine Taylor states that green tea has been used as a medicine in China for at least 4,000 years.
Today, scientific research in both Asia and the west is providing hard evidence for the health benefits long associated with drinking green tea. For example, in 1994 the Journal of the National Cancer Institute published the results of an epidemiological study indicating that drinking green tea reduced the risk of esophageal cancer in Chinese men and women by nearly sixty percent. University of Purdue researchers recently concluded that a compound in green tea inhibits the growth of cancer cells. There is also research indicating that drinking green tea lowers total cholesterol levels, as well as improving the ratio of good (HDL) cholesterol to bad (LDL) cholesterol.
To sum up, here are just a few medical conditions in which drinking green tea is reputed to be helpful:
* cancer
* rheumatoid arthritis
* high cholesterol levels
* cariovascular disease
* infection
* impaired immune function
What makes green tea so special?
The secret of green tea lies in the fact it is rich in catechin polyphenols, particularly epigallocatechin gallate (EGCG). EGCG is a powerful anti-oxidant: besides inhibiting the growth of cancer cells, it kills cancer cells without harming healthy tissue. It has also been effective in lowering LDL cholesterol levels, and inhibiting the abnormal formation of blood clots. The latter takes on added importance when you consider that thrombosis (the formation of abnormal blood clots) is the leading cause of heart attacks and stroke.
Links are being made between the effects of drinking green tea and the "French Paradox." For years, researchers were puzzled by the fact that, despite consuming a diet rich in fat, the French have a lower incidence of heart disease than Americans. The answer was found to lie in red wine, which contains resveratrol, a polyphenol that limits the negative effects of smoking and a fatty diet. In a 1997 study, researchers from the University of Kansas determined that EGCG is twice as powerful as resveratrol, which may explain why the rate of heart disease among Japanese men is quite low, even though approximately seventy-five percent are smokers.
Why don't other Chinese teas have similar health-giving properties? Green, oolong, and black teas all come from the leaves of the Camellia sinensis plant. What sets green tea apart is the way it is processed. Green tea leaves are steamed, which prevents the EGCG compound from being oxidized. By contrast, black and oolong tea leaves are made from fermented leaves, which results in the EGCG being converted into other compounds that are not nearly as effective in preventing and fighting various diseases.
Other Benefits
New evidence is emerging that green tea can even help dieters. In November, 1999, the American Journal of Clinical Nutrition published the results of a study at the University of Geneva in Switzerland. Researchers found that men who were given a combination of caffeine and green tea extract burned more calories than those given only caffeine or a placebo.
Green tea can even help prevent tooth decay! Just as its bacteria-destroying abilities can help prevent food poisoning, it can also kill the bacteria that causes dental plaque. Meanwhile, skin preparations containing green tea - from deodorants to creams - are starting to appear on the market.
Harmful Effects?
To date, the only negative side effect reported from drinking green tea is insomnia due to the fact that it contains caffeine. However, green tea contains less caffeine than coffee: there are approximately thirty to sixty mg. of caffeine in six - eight ounces of tea, compared to over one-hundred mg. in eight ounces of coffee.
“宁可三日无米，不可一顿无茶”（中国古谚语）
还有其它食物或者饮料能像绿茶一样有益于我们的健康吗？中国人自古以来就懂得利用绿茶的医用价值，并用于治疗头痛和意志消沉等。Nadine Taylor在她《绿茶：健康的天然奥秘》一书中说道，中国早在4000年前就已将绿茶入药。
长久以来，人们都将饮用绿茶与健康联系起来，如今亚洲和西方的科学研究正为此提供了有力的证据。例如，1914年国家癌症研究所发表了一项关于流行病学的研究，结果表明饮用绿茶使中国男性和女性中食道癌的发病率降低将近60％。最近，普渡大学的学者研究发现，绿茶中的一种化合物能够抑制癌症细胞的生长。同样有研究表明，饮用绿茶能降低总胆固醇水平和提高有益胆固醇（高密度脂蛋白）与有害胆固醇（低密度脂蛋白）的比率。
总而言之，饮用绿茶是对很多疾病都有益处，这里仅做一些列举：
·癌症
·风湿性关节炎
·高胆固醇
·心血管疾病
·传染病
·免疫功能受损
什么使绿茶如此特别？
绿茶的秘密在于它富含儿茶素，特别是没食子儿茶素没食子酸酯(EGCG)。EGCG是一种强抗氧化剂：不仅能抑制癌细胞生长，杀灭癌细胞，同时也不损害健康的组织。除此之外还能有效地降低LDL胆固醇水平和抑制血块形成异常。而血栓症（异常血块的形成）正是导致心脏病和中风的主要原因，考虑到这点，后者就显得尤为重要。
人们将饮用绿茶的功效与“法兰西悖论”联系起来。多年以来，研究人员都无法解释这个事实，尽管法国人的日常饮食富含脂肪，但是心脏病的发病率却比美国人低。发现答案原来是红酒中含有多酚物质白藜芦醇，它能够限制吸烟和脂肪所带来的副作用。在1997年的一项研究中，堪萨斯大学的研究员测定出EGCG的功效是白藜芦醇的两倍，这就解释了为什么日本人中将近75％都是吸烟者，而心脏病的发病率却十分低。
为什么其它中国茶没有类似的保健功能？绿茶、乌龙茶和红茶均取自山茶花的叶子，是绿茶的加工方式使它显得与众不同。绿茶的茶叶通过蒸煮防止了EGCG化合物被氧化。相比之下，红茶和乌龙茶的茶叶都是发酵而成的，这会使EGCG转化为其它化合物，预防和治疗各种疾病的效果都远不如前者�！�
其它益处
新的证据表明绿茶甚至能帮助节食者。1999年11月，美国临床营养学报刊登了一项瑞士日内瓦城大学的研究结果。研究员发现，结合咖啡因和绿茶提取物使用的人比单独使用咖啡因或安慰剂的人能燃烧更多的卡路里。
绿茶甚至能帮助预防蛀牙！正如它的杀菌能力可以防止食物中毒，它也能杀灭引起牙菌斑的细菌。同时，从除臭剂到乳霜——各种绿茶配方的护肤品正开始在市场上出现。
不良影响
关于饮用绿茶的不良影响，到目前为止唯一报导的就是失眠，因为绿茶中含有咖啡因。不过，绿茶中的咖啡因含量要比咖啡低：6到8盎司茶里大约含有30到60毫克咖啡因，相比之下，8盎司咖啡里就含有超过100毫克咖啡因。
