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Absence of an inhibitory effect of a vegetables-fruit mixture on the initiation and promotion phases of azoxymethane-induced colorectal carcinogenesis in rats fed low- or high-fat diets
- Rijnkels, J.M., Hollanders, V.M.H., Woutersen, R.A., Koeman, J.H., Alink, G.M.
- Nutrition and cancer 1998 v.30 no.2 pp. 124-129
- carcinogenesis, nutrient intake, food intake, duodenum, rats, dietary fat, experimental diets, adenocarcinoma, body weight, cecum, azoxymethane, jejunum, animal models, adenoma, colorectal neoplasms, vegetables, mixtures, incidence, dietary supplements
- The potential inhibitory effects of a vegetables-fruit mixture on the initiation and promotion phases of azoxymethane-induced colorectal carcinogenesis were examined in rats fed low- or high-fat diets. Rats were fed low-fat diets (20 energy percent, Diets A and B) or high-fat diets (40 energy percent, Diets C and D), supplemented with a vegetables-fruit mixture (19.5% wt/wt, Diets B and D) or unsupplemented (Diets A and C) for 36 weeks. After the animals were maintained on the respective diets for four weeks, they were given three weekly injections of azoxymethane at 15 mg/kg body wt sc. Eight weeks after the start of the study, animals maintained on Diet A were switched to Diet B or C or maintained on the same diet. Animals maintained on Diet B or D were switched to Diet A or C, respectively. Furthermore, animals maintained on Diet C were switched to Diet A or D or maintained on the same diet. Multiplicity of colorectal tumors did not differ between groups fed a vegetables-fruit mixture during the initiation or the promotion phase (Group B leads to A vs. Group A leads to B; Group D leads to C vs. Group C leads to D). However, multiplicity was significantly lower in animals fed low-fat diets than in animals fed high-fat diets in combination with a vegetables-fruit mixture (Group A leads to B/B leads to A vs. Group C leads to D/D leads to C). Furthermore, multiplicity was significantly increased in groups fed a high-fat diet during the promotion phase only in comparison with animals fed a low-fat diet during the whole experiment (Group A leads to C vs. Group A leads to A). No other differences in multiplicity or tumor incidences were observed among the eight experimental groups.