Vogel V G, McPherson R S
Department of Medical Oncology, University of Texas M.D. Anderson Cancer Center, Houston.
Hematol Oncol Clin North Am. 1989 Mar;3(1):35-63.
Epidemiologic studies of the relationship of diet to cancer etiology are hampered by methodologic difficulties which can be overcome by careful trial design. The use of appropriate dietary assessment instruments is necessary to minimize bias and improve accuracy of diet assessment. Population studies implicate dietary fat intake in the etiology of colorectal carcinogenesis, and the incidence of colorectal malignancies around the world is positively correlated with meat and fat consumption and total calorie intake. Retrospective studies of fat intake yield equivocal results, whereas prospective studies have failed to show a relationship between fat intake and colon cancer risk. An inverse relationship exists between fiber consumption and colorectal cancer incidence and mortality rates. The positive observational studies are supported by laboratory studies of experimental carcinogenesis which show a greater number of tumors in animals fed high-fat or high-calorie diets. Increased fiber intake appears to offer some protection against colorectal cancer. Plausible mechanisms have been proposed in animals for the role of fat and fiber in colorectal carcinogenesis; the mechanisms in human populations await further description. The interrelationships between fat consumption and consumption of dietary fiber and micronutrients have made it difficult to assess the roles of these substances in the etiology of colorectal cancer. Calcium offers protection in animal systems, and the data in humans are suggestive but not yet conclusive. Data on the role of alcohol in colorectal carcinogenesis remain inconclusive. Little evidence exists for a protective effect of retinoids and carotenoids; the evidence for selenium and vitamin C is limited and evolving.
饮食与癌症病因关系的流行病学研究因方法学上的困难而受阻，不过通过精心的试验设计这些困难是可以克服的。使用合适的饮食评估工具对于尽量减少偏差和提高饮食评估的准确性是必要的。人群研究表明饮食中脂肪摄入与结直肠癌发生病因有关，并且世界各地结直肠恶性肿瘤的发病率与肉类、脂肪消费及总热量摄入呈正相关。对脂肪摄入的回顾性研究结果不明确，而前瞻性研究未能显示脂肪摄入与结肠癌风险之间存在关联。纤维摄入量与结直肠癌发病率及死亡率之间存在负相关关系。积极的观察性研究得到了实验性致癌作用实验室研究的支持，这些研究表明喂食高脂肪或高热量饮食的动物体内肿瘤数量更多。增加纤维摄入量似乎能为预防结直肠癌提供一定保护。在动物身上已经提出了脂肪和纤维在结直肠癌发生过程中作用的合理机制；人类群体中的机制有待进一步描述。脂肪消费与膳食纤维及微量营养素消费之间的相互关系使得难以评估这些物质在结直肠癌病因中的作用。钙在动物系统中具有保护作用，人类的数据具有一定启发性但尚未定论。关于酒精在结直肠癌发生过程中作用的数据仍然不明确。类视黄醇和类胡萝卜素具有保护作用的证据很少；关于硒和维生素C的证据有限且仍在不断发展。
