Because of its high degree of resistance to attack by oxygen free radicals, higher levels of oleic acid in an olive oil help keep it fresher for longer, by preventing the formation of peroxidized (rancid) fats. And because your body will absorb any peroxidized fats that you consume and incorporate them into your cells, oleic acid’s superior resistance to free radical attack also protects your cell membranes, proteins, and DNA from being damaged, even as it protects the oil from spoiling.
Also, substituting oleic acid for saturated fatty acids in animal fats improves cholesterol balance,[i][i] and research also suggests that oleic acid may also have more specific health benefits, such as the ability to help regulate healthy blood pressure by altering cellular signaling.[ii][ii],[iii][iii],[iv][iv],[v][v] For these and other reasons, the US FDA has approved the health claim that “Limited and not conclusive scientific evidence suggests that eating about 2 tablespoons (23 grams) of olive oil daily may reduce the risk of coronary heart disease due to the monounsaturated fat in olive oil.”
[i][i] Mensink RP, Zock PL, Kester AD, Katan MB. Effects of dietary fatty acids and carbohydrates on the ratio of serum total to HDL cholesterol and on serum lipids and apolipoproteins: a meta-analysis of 60 controlled trials. Am J Clin Nutr. 2003 May;77(5):1146-55.
[ii][ii] Terés S, Barceló-Coblijn G, Benet M, Alvarez R, Bressani R, Halver JE, Escribá PV. Oleic acid content is responsible for the reduction in blood pressure induced by olive oil. Proc Natl Acad Sci U S A. 2008 Sep 16;105(37):13811-6.
[iii][iii] Alonso A, Martínez-González MA. Olive oil consumption and reduced incidence of hypertension: the SUN study. Lipids. 2004 Dec;39(12):1233-8.
[iv][iv] Estruch R, Martínez-González MA, Corella D, Salas-Salvadó J, Ruiz-Gutiérrez V, Covas MI, Fiol M, Gómez-Gracia E, López-Sabater MC, Vinyoles E, Arós F, Conde M, Lahoz C, Lapetra J, Sáez G, Ros E; PREDIMED Study Investigators. Effects of a Mediterranean-style diet on cardiovascular risk factors: a randomized trial. Ann Intern Med. 2006 Jul 4;145(1):1-11.
[v][v] Ruíz-Gutiérrez V, Muriana FJ, Guerrero A, Cert AM, Villar J. Plasma lipids, erythrocyte membrane lipids and blood pressure of hypertensive women after ingestion of dietary oleic acid from two different sources. J Hypertens. 1996 Dec;14(12):1483-90.