Effect of alterations in the quality and quantity of dietary fat on 1,2-dimethylhydrazine-induced colon tumorigenesis in rats.

The effect of alterations in the quality and quantity of dietary fat on 1,2-dimethylhydrazine-induced colon cancer in rats was studied. Weanling Sprague-Dawley rats were fed semipurified diets containing 24% beef fat, 24% corn oil, 24% Crisco, or the three fats in equal parts to make a total of 5% fat with other macronutrients and micronutrients adjusted to balance the ratios of nutrient to calorie. After 4 weeks of dietary treatment, all rats, except vehicle-treated animals, received 1,2-dimethylhydrazine (15 mg/kg) by gavage, once a week for 5 weeks. The animals were fed the experimental diets until intestinal tumors developed, and surviving animals were sacrificed at 60 weeks. There was no effect of any of the high-fat diets tested on intestinal tumor incidence, latency, size, or frequency. All groups contained the same proportion of adenomas (less than 3%) as well as adenocarcinomas classified as mucinous. In the group fed 24% Crisco, tumors occurred with greater frequency in the proximal section of the colon than in lower segments, but the distribution was approximately uniform in the other groups. Cumulative probability of death with colon carcinoma was lowest in the 24% Crisco group, but the other high-fat groups did not differ significantly from the 5% mixed fat group nor from one another.