To elucidate the influence of diet on colorectal carcinogenesis, 1225 subjects with cancer of the colon, 728 with cancer of the rectum and 4154 controls, hospitalized with acute non-neoplastic diseases, were interviewed between 1992 and 1996 in six Italian areas.The validated food frequency questionnaire included 79 questions on food items and recipes which were grouped into 16 food groups. After allowing for nondietary confounding factors and total energy intake, a significant trend towards an increasing risk of colorectal cancer with increasing intake was found for bread and cereal dishes (odds ratio for increase of one daily serving 1.11), cakes and desserts (odds ratio 1.02) and refined sugar (odds ratio 1.11). The intake of fish (odds ratio 0.53), raw and cooked vegetables (odds ratios 0.79 and 0.65, respectively) and fruit (odds ratio 0.93) showed an inverse association with risk. Wholemeal bread was consumed by only 12.5% of cases and 13.9% of controls and, at variance with refined bread, did not show a significant direct association with colorectal cancer risk (odds ratio 0.88). In view of these findings, current hypotheses on the carcinogenic effects of refined starchy foods and refined sugar should be revised to take into account the digestive physiology of carbohydrates and the possible relationship between insulin and colon cancer. The beneficial influence of most vegetables is confirmed, and a possible difference between refined and wholemeal bread is suggested
