Nutritional Studies of Hardened Fish Oil. I

Abstract

To examine the nutritional and physiological effects of dietary hardened fish oil (HFO), three groups of weanling male rats were fed diets containing 20 % HFO, soybean oil (SO) or hardened soybean oil (HSO) for 5 days and 8 weeks. The effects of these fats on weight gain, serum lipids and fatty acid profiles of the liver, heart and adipose tissue were compared.1) No rats showed abnormal external appearances or heart and liver condition at autopsy. Body weight gain was highest in the SO group and lowest in the HFO group, the HSO group showing intermediate gain. The relative liver weight of the HFO group increased temporarily after 5 days but became comparable to those of the other groups with prolonged feeding. Triglyceride and cholesterol serum levels were higher in the SO group than in the other groups.2) In the livers of rats fed HFO and HSO, trans fatty acids, comprised primarily of monounsaturated acids, were detected, but their amounts decreased after a prolonged period of feeding. Trans isomers of 20 : 1 and 22 : 1, both characteristic of HFO, could hardly be detected in the HFO group. Although percentages of n-6 polyunsaturated fatty acids were very low and remained unchanged in the HFO group, they increased in the HSO group as the time of the feeding period progressed. Essentially the same was noted for heart lipid content.3) In the SO group, detectable amounts of traps acids, absent from the dietary fat, were detected in liver and heart lipids, and also in adipose tissue but to a lesser degree.4) These observations indicate long chain traps monoene fatty acids in HFO to apparently have no particularly unfavorable effects on rats.