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在发达国家,结直肠癌是最常见的癌症之一。世界各地该病发生率高低不一(相差20倍),这提示其发生可能与环境特别是饮食因素密切相关。1969年Burkitt认为非洲人之所以结肠癌危险低是因其食物中含有较多不吸收性纤维的缘故。其后有13项病例对照研究表明纤维摄入与结肠癌危险低相关。但也观察到一些相反的倾向。迄今一直未能阐明蔬菜和水果高摄入者癌危险低是否归因于特殊种类或单独哪一种营养素,换言之,尚无证据表明癌危险降低是由于纤维本身所致。 高度增殖是结直肠癌发生的一种重要早期改变。
In developed countries, colorectal cancer is one of the most common cancers. The incidence of this disease varies from place to place around the world (a difference of 20 times), which suggests that its occurrence may be closely related to the environment, especially dietary factors. In 1969 Burkitt thought that Africans had a low risk of colon cancer because their food contained more non-absorbable fibers. Thirteen subsequent case-control studies showed that fiber intake was associated with a low risk of colon cancer. However, some opposite tendencies were also observed. It has so far been impossible to elucidate whether the low cancer risk of high intakes of vegetables and fruits is attributed to a particular species or to which nutrients alone. In other words, there is no evidence that the reduction in cancer risk is due to the fibers themselves. High proliferation is an important early change in colorectal cancer.