Serum lipid responses to simultaneous alterations in dietary palmitic and oleic acids in the absence and presence of dietary cholesterol in the hamster

Three separate studies, each of 6-week duration, were carried out to assess the effects of simultaneously lowering palmitic acid (PA) and increasing oleic acid (OA) levels in the diets on serum lipid responses in the absence and in the presence of dietary cholesterol in the hamster. Our results show that in the absence of dietary cholesterol, refined, bleached and deodorized palm oil (RBDPO), a new hybrid crude palm oil (HBCPO) and olive oil (OLO) produced similar serum lipid responses in the hamster. In the presence of low level (0.05%,w/w) of dietary cholesterol, RBDPO, HBCPO, OLO and high-oleate sunflowerseed oil (HOSFLO) again produced no difference in serum lipid responses. Since RBDPO and HBCPO are high in PA and OLO and HOSFLO are high in OA, the above results indicate that PA and OA have similar nonhypercholesterolemic effect in cholesterol-free and low cholesterol dietary conditions. However, in the presence of high level (2%,w/w) of dietary cholesterol, OLO and HOSFLO lowered serum total. cholesterol level significantly (P0.05) than RBDPO and HBCPO. High density lipoprotein cholesterol (HDL-C) level was not significantly affected. Serum triacylglycerol (TAG) levels in the RBDPO and HBCPO groups were much higher than that of OLO and HOSFLO groups; hut due to large standard deviations, statistical significance was not achieved. Our results further show that serum TAG levels in all four dietary groups were raised more than two-fold in the presence of low level of dietary cholesterol as compared to that seen in the absence of dietary cholesterol. Moreover, further increase in dietary cholesterol had no positive effect on the serum TAG level. Results from these studies show that PA and OA exhibited nonhypercholesterolemic effect in the absence and presence of low level of dietary cholesterol in the hamster, and PA exhibited hypercholesterolemic effect while OA showed hypocholesterolemic effect in the presence of high level of dietary cholesterol