The safety of ethyl oleate is supported by a 91-day feeding study in rats

Abstract

The purpose of this study was to determine the safety of ethyl oleate (EO) in a 91-day feeding study in Sprague–Dawley rats. EO was mixed into AIN-93G purified diet at levels of 0, 3.3, 6.7, and 10% by weight (the high-dose males and females consumed 5.5 and 6.1 g/kg/day EO, respectively). All diets were calorie- and fat-matched using high oleic safflower oil (HOSO) as the control fat. The study design followed the 1993 FDA draft “Redbook II” guidelines (Toxicological Principles for the Safety Assessment of Direct Food Additives and Color Additives Used in Food). There were 20 male and 20 female rats per group. EO in the diet was well tolerated and there were no toxicologically significant findings in any of the measured parameters (clinical observations, body weight gains, appearance of the feces, ophthalmic examinations, hematology, clinical chemistry, urinalysis, organ weights, histopathology, or male and female reproductive assessments). Mortality was limited to three males during the course of the study whose cause of death was unrelated to test material administration. The terminal body weight of the mid- and high-dose females was approximately 10% lower than that of the control group. This finding does not represent a toxicologically significant effect because rats on the EO diets gained more weight during the course of the study than historical control data on this strain of rats. The lower body weight relative to control rats is directly related to lower food consumption relative to the controls. The lower food consumption relative to controls is fully consistent with a decrease in the palatability of the EO-containing food versus the triglyceride-containing food. This conclusion is based on (1) a decrease in food consumption was noted within the first week (consistent with palatability preferences), (2) there was not a dose–response with regard to food consumption (mid-dose consumed less than high-dose), (3) the lack of cumulative decreases in food consumption which often are observed with toxicity, and (4) anecdotal experiences in our lab show that rats prefer diets containing high triglyceride fat over high EO-fat. Hepatocellular vacuolation typical of fat accumulation was noted for both control and high-dose animals. The incidence and severity of the vacuolation were higher for animals given 10% HOSO (controls) than for the animals given 10% EO. Serum calcium and phosphorous levels in high dose males were slightly, but statistically significantly, lower than in the controls. There was a dose-related increase in fecal fat concentration in both sexes from approximately 9% (control) to 18% in males, and from 4 (control) to 13% in females There were no visually obvious differences with regard to feces quality or quantity at any level of EO in the diet (i.e., color, diarrhea, weight, etc.). The increase in fat most likely represents small amounts of unabsorbed EO at the mid- and high-dose (estimates of EO absorption in this study are >80%). The No Observable Adverse Effect Level was determined to be 10% EO when administered daily in the diet for 91-days (approximately 6 g EO/kg bw/day).