Towards the dietary prevention of cancer: contributions of epidemiology.

There may be a considerable potential for the prevention of cancer through dietary modifications or chemo-prevention strategies. The epidemiological methods which have been used in the study of the relation between diet and cancer are briefly reviewed and the scientific basis for major hypotheses linking diet to cancer are summarized. Clinical trials, now being considered to assess the potential for the prevention of cancer by dietary supplementation or modification, do not have many of the uncertainities of other methods, yet there are many potential difficulties in both the conduct and interpretation of such trials. These limitations are discussed as well as the problem in making general dietary recommendations for the prevention of cancer based on current knowledge. A more complete understanding of the effect of diet on cancer risk will likely emerge only through a more integrated and interdisciplinary approach in future studies.