Prospects for the prevention of colorectal cancer

Cancer research has been productive in developing new knowledge on the role of diet in cancer. It is clear from epidemiologic observations that diet is the principal factor in the cause of colorectal cancer in most people. Therefore, a significant reduction in incidence is possible in countries where the disease is common. The ingestion of excessive amounts of fat appears to be the major factor that promotes cancer development. Animal studies confirm this and have recently shown that the sources of fat vary in the degree of their promotional effect. Fiber is generally considered to inhibit cancer but it is now clear that only some types of fiber are effective. These include whole grain cereals, and fruit and vegetables containing large amounts of uronic acid. In addition to fiber, a number of micronutrients, chemicals, and drugs have been found to be effective inhibitors. It is clear that the basic information concerning dietary changes that can reduce colorectal cancer incidence in this country has been uncovered. Additional information is needed about specific details of dietary guidelines. These include identification of the best mixture of sources of fat and how to incorporate such a mixture in the diet. Substances in foods need to be identified that, when included in the diet, help to lower cancer risk. People at high risk may require an additional supplement of inhibitors. New epidemiologic studies and human intervention trials should provide the necessary information to design dietary guidelines that are more specific than current ones.