Oxidized unsaturated fatty acids may contribute to the pathogenesis of atherosclerosis. In the present study, we examined the effects of heated palm oil mixed with 2% cholesterol diet on serum lipid profile, homocysteine and thiobarbituric acid reactive substances (TBARS) levels in estrogen-deficient rats. Twenty-four female Sprague Dawley rats were ovariectomized and then were divided equally into four groups. The control group was given 2% cholesterol diet only throughout the study period. The three treatment groups received 2% cholesterol diet fortified with fresh, once-heated or five-times-heated palm oil,
respectively. Serum TBARS, lipid profile and homocysteine levels were measured prior to ovariectomy and at the end of four months of the study. Five-times-heated palm oil caused a significant increase in TBARS and total cholesterol (TC) compared to control (F = 22.529, p < 0.05). There was a significant increase in serum homocysteine in the control as well as five-times heated palm oil group compared to fresh and once-heated palm oil groups (F = 4.432, p < 0.05). The findings suggest that repeatedly heated palm oil increase lipid peroxidation and TC. Ovariectomy increases the development of atherosclerosis as seen in this study. Feeding with fresh and once-heated palm oil does not cause any deleterious effect but repeatedly heated oil may be harmful because it causes oxidative damage thereby predisposing to atherosclerosis.