结直肠癌常被看作西方发达国家的一种疾病。美国和加拿大发病率最高,亚洲、非洲和南美洲发病率最低。世界范围发病率的差异,加之低发区来到高发区的移民有患结直肠癌的高度危险性,这些强烈提示环境因素起主要病因作用。直到最近,结直肠癌的病因学说几乎总是集中在饮食,尤其是高脂肪和/或低纤维饮食上。经研究证实,这两种因素影响胆汁分泌、结肠微生物群和酶的活性,因而影响了粪便中致癌剂的浓度。 Colorectal cancer is often seen as a disease in Western developed countries. The United States and Canada have the highest incidence rates, with the lowest incidence rates in Asia, Africa, and South America. The worldwide incidence of morbidity, combined with the high risk of developing colorectal cancer among immigrants in low-incidence areas, strongly suggests that environmental factors play a major role. Until recently, the etiology of colorectal cancer almost always focused on diet, especially on high-fat and/or low-fiber diets. Studies have confirmed that these two factors affect the activity of bile secretion, colon microbiota and enzymes, and thus affect the concentration of carcinogens in the feces.