A NEW DIETARY MODEL TO STUDY COLORECTAL CARCINOGENESIS - EXPERIMENTAL-DESIGN, FOOD PREPARATION, AND EXPERIMENTAL FINDINGS

Experimental dietary studies of human colorectal carcinogenesis are us ually based on the AIN-76A diet, which is dissimilar to human food in source, preparation, and content. The aims of this study were to exami ne the feasibility of preparing and feeding rats the diet of a specifi c human population at risk for colorectal neoplasia and to determine w hether changes in the colonic morphology and metabolic contents would differ from those resulting from a standard rat diet. The mean daily f ood intake composition of a previously evaluated adenoma patient case- control study was used for the ''human adenoma'' (HA) experimental die t. Foods were prepared as for usual human consumption and processed by dehydration to the physical characteristics of an animal diet. Sixty- four female Sprague-Dawley rats were randomized and fed ad libitum the HA or the AIN-76A diet. Every eight weeks, eight rats from each group were sacrificed, and the colons and contents were examined. Analysis of the prepared food showed no significant deleterious changes; food i ntake and weight gain were similar in both groups. Compared with the c ontrols, the colonic contents of rats fed the HA diet contained signif icantly less calcium, concentrations of neutral sterols, total lipids and cholic and deoxycholic acids were increased, and there were no col onic histological changes other than significant epithelial hyperproli feration. This initial study demonstrated that the HA diet can be succ essfully processed for feeding to experimental animals and is acceptab le and adequate for growth but induces significant metabolic and hyper proliferative changes in the rat colon. This dietary model may be usef ul for studies of human food, narrowing the gap between animal experim entation and human nutritional research.