ABSTRACT
This chapter focuses on the interpretation of carcinogenicity of so-called ordinary or sporadic colorectal tumors in humans and in chemically induced lesions in rodent models in relation to dietary factors, alcohol consumption, and smoking. Extensive human and experimental data over the twentieth century strongly suggest that dietary factors are relevant to the etiology of both colorectal cancer and its major precursor lesion, colorectal adenomas. There are two major dietary hypotheses, which, put in a simplified form, may be called the “meat/protein/fat/energy/fried/grilled food risk” and the “vegetable/fruit/cereal/fiber/starch/phytochemical food protection” hypotheses. Since 1957 over 90 epidemiological studies have examined the relationship between alcohol consumption and colorectal tumor risk. These studies indicate with moderate consistency that long-continued alcohol consumption presents about a twofold risk for both colorectal adenomas and colorectal cancer. The scientific basis for a causal link between colorectal tumors and smoking is recent and was first provided by a study of colorectal adenomas from Norway in 1987.
