Effect of high fat and nutrient depleted diets on colon tumor formation in mice.

We investigated the effect of high fat and nutrient depleted diets on the formation of colon tumors in female Swiss mice treated with 1,2-dimethylhydrazine (DMH). Mice received the following diets: control diet (laboratory chow, 5.5% fat) or chow with added starch and/or corn oil so as to supply a fat level of 5.5% (diet F6) or 23% (diet F23), while reducing the level of nutrients and dietary fiber per 100 calories to 61% of the level of the control diet. DMH was given as 5 weekly s.c. injections. Diets were given variously from 6 weeks before the first injection until 7 days after the last one (initiation period) or else for the subsequent 22 weeks until sacrifice of the mice (promotion period). A high fat diet (diet F23 vs. F6) tended to increase adenoma formation when fed during the initiation period but this requires further study. Feeding it in the promotion period increased the incidence of adenocarcinomas. A nutrient depleted diet (diet F6 vs. the control diet) caused a decreased incidence of adenocarcinomas.