Lack of effect of dietary fat on N-nitrosomethyl urea (NMU)-induced colon tumorigenesis in rats

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Abstract
The effect of alterations in the quality and quantity of dietary fat on N-nitrosomethyl urea (NMU)-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. Macronutrients and micronutrients were adjusted to balance the nutrient to calorie ratios. After 4 weeks of dietary treatment, all rats, except vehicle-treated animals received NMU (1.5 mg) via intrarectal instillation, twice a week for 2 weeks. The animals continued receiving the experimental diets until intestinal tumors developed and surviving animals were sacrificed at 43 weeks. There was no effect of any of the high fat diets tested on intestinal tumor incidence, latency, distribution or size. Cumulative probability of death with colon carcinoma did not differ significantly among the dietary groups.