APPLIED NUTRITIONAL INVESTIGATION Dietary Oils High in Oleic Acid but With Different Unsaponifiable Fraction Contents Have Different Effects in Fatty Acid Composition and Peroxidation in Rabbit LDL Julio J. Ochoa, PhD, Jose ´ L. Quiles, PhD, M. C. Ramı ´rez-Tortosa, PhD; Jose ´ Mataix, PhD, and Jesu ´s R. Huertas, PhD From the Institute of Nutrition and Food Technology, the Department of Physiology, and the Department of Biochemistry and Molecular Biology, University of Granada, Granada, Spain OBJECTIVE: We investigated the influence of different edible oils high in oleic acid but with different unsaponifiable fractions on the fatty acid composition and lipid peroxidation in plasma and low-density lipoprotein (LDL) in rabbits. METHODS: Thirty-two rabbits were randomly assigned to four groups of eight animals. For 8 wk each group was fed a semisynthetic isoenergetic diet that differed by lipid source (Picual virgin olive oil, Picual virgin olive oil that had been subjected to an exhaustive process of washing, Arbequina virgin olive oil, and sunflower oil high in oleic acid). We analyzed the fatty acid profile, thiobarbituric acid reactive substances, -tocopherol, coenzyme Q, and retinol in plasma and the fatty acid profile, hydroperoxides, -tocopherol, and coenzyme Q in LDL. RESULTS: The two varieties of virgin olive oil behaved differently from the high-oleic sunflower oil, and the effect of the different ratios of oleic acid to linoleic acid in the lipid sources on fatty acid composition in plasma and LDL was significant. With regard to oxidative stress, LDL in the group that ingested the lipid sources with the greatest amount of phenolic compounds showed the highest level of antioxidants (-tocopherol and coenzyme Q; P  0.05) and the lowest susceptibility to lipid peroxidation (P  0.05). CONCLUSION: This study provides evidence in vivo of the considerable antioxidant capacity of the phenolic fraction of virgin olive oil in rabbit LDL and the important role that this unsaponifiable fraction can play in the overall antioxidant benefit attributed to these oils. However, these effects depend on the phenolic content of the oil. Nutrition 2002;18:60 – 65. ©Elsevier Science Inc. 2002 KEY WORDS: unsaponifiable fraction, oleic acid, fatty acid composition, lipid peroxidation, low-density lipoproteins, rabbits INTRODUCTION Atherosclerosis is the principal cause of cardiovascular disease in the Western world. Many epidemiologic studies have correlated the state and composition of low-density lipoproteins (LDLs) with the development of atherosclerotic plaque and, hence, with the higher and lower incidences of cardiovascular disease. 1,2 Chemical and physical alterations of LDL as a result of oxidation increase the atherogenic properties of these lipoproteins. 3–5 Nutritional and biochemical studies have suggested that diet can change suscepti- bility to LDL oxidation by the influence the lipid profile of the lipid source ingested exerts on the lipid profile of these particles and by changing their antioxidant content. 3,5 Thus, several studies have shown that enrichment of lipoproteins with oleic acid, present in olive oil, boosts resistance to oxidation more than does enrich- ment with linoleic acid, present in sunflower oil. 3,5,6 These results in part have given rise to a consumer market for the new vegetable oils enriched with this monounsaturated fatty acid, e.g., sunflower oil high in oleic acid. However, although the composition of fatty acids in these new oils is quite similar to that found in virgin olive oil, significant differences exist, especially in the unsaponifiable fraction (also called non-glyceride). Thus, it should be borne in mind that these oils require refining, a process that brings about, among other effects, a significant loss of the antioxidants in the unsaponifiable fraction. 6–8 This has a signifi- cant effect on oxidative stress and has received little attention to date. Virgin olive oil, a monounsaturated fat widely used in the Mediterranean diet, apart from its high oleic acid content, has an unsaponifiable fraction rich in antioxidant compounds, including phenolic compounds. In fact, this is the only dietary oil that contains these compounds, which contribute considerably to the oxidative stability of this oil. 9 In addition, numerous studies have shown the antioxidative capacity of phenolics, which reduce the susceptibility of LDL and erythrocyte membranes to lipid peroxidation. 10 –12 However, most of those studies have been per- formed in vitro and have used individual phenolic compounds. Virgin olive oil has a wide range of variation in saponifiable This study was supported by the Fundacio ´ n para la Promocio ´ n y Desarrollo del Aceite de Oliva y del Olivar, Jae ´n, Spain. Dietary oils were kindly supplied by COOSUR, S.A., Jaen, Spain. Correspondence to: Julio J. Ochoa-Herrera, PhD, Institute of Nutrition and Food Technology, C/Ramon y Cajal, 4, 18071, Granada, Spain. E-mail: aging@goliat.ugr.es Nutrition 18:60 – 65, 2002 0899-9007/02/$22.00 ©Elsevier Science Inc., 2002. Printed in the United States. All rights reserved. PII S0899-9007(01)00732-8