Effects of high‐fat diet on incidence of spontaneous tumors in Wistar rats

Abstract In a 2.5‐year carcinogenicity study, two groups, both including male and female Wistar rats, were fed two different diets with 4% and 16% fat. In addition to 4% soybean oil, the high‐fat diet contained 12% mono‐ and diglycerides, of which 85% was stearic acid and 13% palmitic acid. There was no difference in food consumption, body weight, weight gain, and longevity between the two groups. A statistically significant increase in the incidence of tumors in the high‐fat group was seen in fibroadenoma of the mammae (female, p = 0.05). No statistically significant difference was seen when the incidence of benign mammary tumors (adenomas and fibroadenomas) was combined, just as the overall incidence of mammary tumors (adenomas, fibroadenomas, and adenocarci‐nomas) was not significantly different between the groups. A statistically significant decrease in the incidence of tumors in the high‐fat group was seen in adenoma of the parathyroid gland (male, p = 0.04) and medullary carcinoma of the adrenal gla...