[Primary prevention of colorectal cancer].

Results from case-control studies and prospective studies suggest that diet is involved in the causation of large bowel cancer either as initiator, promoter or inhibitor of carcinogenesis. Available data are not sufficient to serve as a basis for firm specific dietary advice. In the present situation it is attractive to investigate available hypotheses within the frame work of intervention trials. The adenoma appears to be one of the most appropriate end point of intervention studies. Several arguments indicate that the adenoma-carcinoma sequence is a multistep process. Colorectal cancer could possibly be prevented by intervening in the development of a small adenoma or in the growth into a large adenoma. Four intervention trials have been published so far. One of them suggest a protective effect of antioxidants vitamins on adenoma recurrence and three of them conclude to the absence of effect of these vitamins. A protective effect of lactulose on adenoma recurrence has also been suggested. Three studies are currently evaluating the effect of calcium supplementation on adenoma recurrence or growth of calcium supplementation, three studies the effect of fibre supplements, two studies the effect of antioxidants (one of them with calcium) and two studies the effect of diet intervention. The results of these studies will be available within three years.