INTERACTION OF DIETARY FAT WITH A VEGETABLES-FRUIT MIXTURE ON 1,2-DIMETHYLHYDRAZINE-INDUCED COLORECTAL-CANCER IN RATS

The aim of the present investigation was to study the interaction of d ietary fat in combination with a vegetables-fruit mixture on 1,2-dimet hylhydrazine (DMH)-induced colorectal carcinogenesis in rats. For this purpose, 120 weanling male Wistar rats received a semisynthetic diet without (Groups A and C) or with a vegetables-fruit mixture (Groups B and D; vegetables and fruit content 19.5% wt/wt) for 35 weeks. Diets o f Groups A and B contained 20 energy percent (20e%) fat, whereas diets of Groups C and D contained 40e% fat. The vegetables and fruit used, the amount of fat, and its fatty acid composition were chosen accordin g to the mean consumption values of The Netherlands. After the animals were maintained for four weeks on the respective diets, they were giv en 10 weekly injections of DMH at 50 mg/kg body wt sc. After sacrifice , their colons were removed and examined macroscopically and microscop ically for the presence of tumors. Rats fed high-fat diets developed s ignificantly more tumors than rats fed low-fat diets. Furthermore, alt hough not statistically significant, a lower number of colorectal tumo rs was observed in rats fed a low- or a high-fat diet containing the v egetables-fruit mixture than in rats fed diets without the vegetables- fruit mixture. No differences were observed in intestinal tumor incide nces among all groups. The results suggest that the vegetables-fruit m ixture used in this experiment, present in an amount comparable with t he mean consumption in The Netherlands, has no significant inhibitory effect on the development of colorectal tumors induced by DMH in rats maintained on diets low or high in fat.