Amount and type of fat and energy density of diets may influence
tumor incidences. The purpose of this report is to summarize the influence of
corn oil gavage and different nonpurified diets on spontaneous
tumor incidences in 64 diet and 59
corn oil gavage control groups in two-year studies involving approximately 6,100 control Fischer 344 rats of each sex. The maximum mean
body weight attained during the course of the study, survival at 106 weeks of age, and spontaneous
tumor incidences of groups fed different nonpurified diets with or without
corn oil gavage were summarized and evaluated for differences. Male rats fed NIH-07 open-formula diet with or without
corn oil gavage had significantly higher
body weight, lower survival, and higher incidence of pancreatic acinar cell
tumors than rats fed commercial proprietary diets with or without
corn oil gavage. Female rats fed NIH-07 diet with or without
corn oil gavage had significantly higher
body weights and pancreatic
tumor incidences than groups fed commercial diets. Time-related trends could account for other apparent differences in
tumor incidences between the groups fed commercial and NIH-07 diets.
Corn oil gavage significantly increased the
body weight and pancreatic
tumor incidences but decreased the incidence of
leukemia, a lethal
tumor, which resulted in higher survival in male rats.
Corn oil gavage significantly lowered the
body weight and anterior
pituitary tumor incidence in female rats. The pancreatic acinar cell
tumor incidence appears to be due to a combination of fat intake and
body weight.