Colorectal adenomas and diet: a case-control study. Colorectal Adenoma Study Group.

It has been postulated that high intakes of animal fat and protein and low intakes of fiber, calcium, and antioxidants increase the risk of colorectal cancer. Whether specific types of protein such as that from red meat are important, and whether vegetables might be key protective factors will also be considered in this study. Dietary intake over the past year was studied according to the diet history method by means of a case-control study in 184 cases and matched controls. After adjustment for energy, relative weight, and social class, no associations were found for fat or protein in comparison with either control group. Unexpectedly, carbohydrate intake was inversely related with adenoma risk, the RR being 0.29 (0.10-0.81) for quintile 5 versus 1 in comparison with hospital controls. None of the antioxidants showed a significant protective effect except beta-carotene intake in comparison with hospital controls, the RR being 0.24 (0.11-0.50) for the highest versus the lowest quintile. There was, however, a statistically significant positive association between adenomas and meat consumption with the RR for the highest versus the lowest quintile. There was, however, a statistically significant positive association between adenomas and meat consumption with the RR for the highest versus the lowest quintile of intake being 3.6 (1.7-7.5) in comparison with hospital controls and 4.4 (1.6-12.1) in comparison with population controls. Our data support the protective role for carbohydrate intake and of beta-carotene intake in the etiology of colorectal adenomas and show a strong increased risk for developing adenomas in those with high meat intake.