茶叶与防癌

饮茶与人类肿瘤发生的关系引起了国内外学者的普遍兴趣，许多学者从肿瘤的起动、促发和增殖阶段对茶叶进行了抗突变性试验研究。结果表明所选用的样品包括绿茶、乌龙茶、红茶、花茶以及所提供的茶叶组分茶多酚，儿茶素等对一些广谱的化学致癌物均有明显的抑制作用，而且对一些未明确的化合物的致突变物也有抑制作用。抗肿瘤作用试验研究表明，茶叶及其组分能抑制多种化学致癌物对实验动物（大鼠、小鼠）的致癌作用，包括食道、胃、肠、肺、肝和皮肤等部位，同时也能抑制小鼠体内移植性肿瘤的生长和恶性肿瘤的转移和浸润。流行病学研究方面，各项癌症发生与饮茶之间相关性的结果并不一致，东西方一些流行病学家持不同看法，其原因主要是由于影响人类癌症发生的因素很多，如果对混合因素控制不当，则很难得出正确的结果。为此需开展一些有严格控制的流行病学的研究（特别是前瞻性研究和人群干预试验）来阐明饮茶究竟对人类癌症有无防治作用。

Tea and cancer prevention

The relationship between tea drinking and human cancer has attracted much interest in scientific community, The antimutagenicity of tea has been studied based on the multi-stage carcinogenesis theory,i.e. initiation, promotion and progression, The results demonstrate that water extracts of various teas(green,oolong,black,jasmine) as well as tea polyphenols and catechins were significantly effective in inhibiting the mutagenicity of a wide spectrum of mutagens, including those not well defined chemical mixtures, Animal studies indicate that tea and its components significantly inhibited the carcinogenicity of various chemical carcinogens in rats and mice. The cancer sites included the esopagus, stomach, intestine,lung, liver,skin,etc. It was also shown that tea inhibited the growth of transplantable tumors and tumor metastasis in mice. However, the results of epidemiological studies on tea and human cancer were inconsistent. Different views exist between scientists in the east and west. The main reason may be related to the complex etiological factors in human cancer occurrence and uncontrolled confounding factors. Therefore, well-controlled epidemiological studies(especially prospective and intervention studies) are needed to clarify the preventive effects of tea drinking on human cancer.