Modulation of dietary fat‐enhanced colorectal carcinogenesis inN‐methyl‐N‘‐nitro‐N‐nitrosoguanidine‐treated rats by a vegetables‐fruit mixture

The modulation of a vegetables-fruit mixture on N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced colorectal carcinogenesis was studied in rats maintained on a low- or a high-fat diet. For this purpose, 120 rats received a semisynthetic diet without (Groups A and C) or with a vegetables-fruit mixture (19.5% wt/wt, Groups B and D) for 35 weeks. Diets of Group A and B contained 20 (low) energy percent (20e%) fat, whereas diets of Groups C and D contained 40e% (high) fat. Between Weeks 4 and 9 the animals were given weekly intrarectal instillations of 6 mg MNNG/kg body wt. The colorectal adenocarcinoma incidences showed a significant decrease in animals fed high-fat diets with a vegetables-fruit mixture compared with animals fed a high-fat diet alone. Furthermore, without a vegetables-fruit mixture, diets high in fat caused a significant increase in adenocarcinoma incidence compared with diets low in fat. Although not significant, the adenoma incidences tended to be lower in animals fed a vegetables-fruit mixture than in animals maintained on a diet without this mixture. The results demonstrate that a vegetables-fruit mixture has a significant inhibitory potency on the development of colorectal tumors induced by MNNG in rats fed diets high in fat.