Objective:To investigate the effects of different dietary fat and oils(differing in their degree of saturation and unsaturation)on lipid peroxidation in liver and blood of rats.Methods:The study was conducted on SO albino rats that were randomly divided into 5 groups of 10 animals.The groups were fed on dietary butter(Group I),margarine(Croup II),olive oil(Group III),sunflower oil(Group IV)and com oil(Group V)for 7 weeks.After 12 h of diet removal,livers were excised and blood was collected to measure malondialdehyde(MDA)levels in the supernatant of liver homogenate and in blood.Blood superoxide dismutase activity(SOD),glutathione peroxidase activity(GPx),serum vitamin E and total antioxidant capacity(TAC)levels were also measured to determine the effects of fats and oils on lipid peroxidation.Results:The results indicated that no significant differences were observed in SOD activity,vitamin E and TAC levels between the five groups.However,there was significant decrease of GPx activity in groups IV and V when compared with otlier groups.The results indicated that feeding corn oil caused significant increases in liver and blood MDA levels as compared with other oils and fats.There were positive correlations between SOD and GPx,vitamin E and TAC as well as between GPx and TAC(r:0.743;P<0.001)and between blood MDA and liver MDA(r:0.897;P<0.00l).The results showed also negative correlations between blood MDA on one hand and SOD,GPx,vitamin E and TAC on the other hand.Conclusions:The results demonstrated that feeding oils rich in polyunsaturated fatly acids(PUFA)increases lipid peroxidation significantly and may raise the susceptibility of tissues to free radical oxidative damage. Objective: To investigate the effects of different dietary fat and oils (differing in their degree of saturation and unsaturation) on lipid peroxidation in liver and blood of rats. Methods: The study was conducted on SO albino rats that were randomly divided into 5 groups of 10 animals.The groups were fed on dietary butter (Group I), margarine (Croup II), olive oil (Group III), sunflower oil (Group IV) and com oil (Group V) for 7 weeks. After 12 h of diet removal, livers were collected to measure malondialdehyde (MDA) levels in the supernatant of liver homogenate and in blood. Blood superoxide dismutase activity (SOD), glutathione peroxidase activity (GPx), serum vitamin E and total antioxidant capacity (TAC ) levels were also measured to determine the effects of fats and oils on lipid peroxidation. Results: The results indicated that no significant differences were observed in SOD activity, vitamin E and TAC levels between the five groups. However, there was a significant decrease of GPx activity in groups IV and V when compared with otlier groups. The results indicated that significant corn increases in liver and blood MDA levels as compared with other oils and fats. There were positive correlations between SOD and GPx, vitamin E and TAC as well as between GPx and TAC (r: 0.743; P <0.001) and between blood MDA and liver MDA (r: 0.897; P <0.00l). The results showed also negative correlations between blood MDA on one hand and SOD, GPx, vitamin E and TAC on the other hand. Conclusions: The results was that feeding oils rich in polyunsaturated fatly acids (PUFA) increases lipid peroxidation significantly and may raise the susceptibility of tissues to free radical oxidative damage.