Determination of glycerophospholipids in vegetable edible oils: Proof of concept to discriminate olive oil categories.
Criado-Navarro I, Mena-Bravo A, Calderón-Santiago M, Priego-Capote F.
Food Chem. 2019 Nov 30;299:125136. doi: 10.1016/j.foodchem.2019.125136.

Enzymatic Synthesis of Refined Olive Oil-Based Structured Lipid Containing Omega -3 and -6 Fatty Acids for Potential Application in Infant Formula.
Li R, Sabir JS, Baeshen NA, Akoh CC.
J Food Sci. 2015 Nov;80(11):H2578-84. doi: 10.1111/1750-3841.13075.

Effect of storage on refined olive oil composition: stabilization by addition of chlorophyll pigments and squalene.
Rigane G, Bouaziz M, Sayadi S, Salem RB.
J Oleo Sci. 2013;62(12):981-7.

Effect of virgin and refined olive oil consumption on gut microbiota. Comparison to butter.
Hidalgo M, Prieto I, Abriouel H, Cobo A, Benomar N, Gálvez A, Martínez-Cañamero M.
Food Res Int. 2014 Oct;64:553-559. doi: 10.1016/j.foodres.2014.07.030

Micro-encapsulation of refined olive oil: influence of capsule wall components and the addition of antioxidant additives on the shelf life and chemical alteration.
Calvo P, Castaño AL, Lozano M, González-Gómez D.
J Sci Food Agric. 2012 Oct;92(13):2689-95. doi: 10.1002/jsfa.5689.

Per os administered refined olive oil and marine PUFA-rich oils reach the cornea: possible role on oxidative stress through caveolin-1 modulation.
Dutot M, Liang H, Martin C, Rousseau D, Grynberg A, Warnet JM, Rat P.
Nutr Metab (Lond). 2009 Nov 23;6:48. doi: 10.1186/1743-7075-6-48.

Refined olive oil is produced by a chemical process.

Olive oil is the predominant source of fat in the Mediterranean diet. The healthy properties of this oil have often been attributed to its high content of monounsaturated fatty acids. Recent evidence has shown that the minor components of olive oil, in particular phenols, contribute to the beneficial effects of this source of fat.  

Compared to extra virgin olive oil, there are no phenols in refined olive oil, the presence of squalene is lower and the presence of monounsaturated acids is lower. The more refined the oil is, the lower the presence of substances that are beneficial for health.

This table provides clear evidence of the diversity of health components in the two oils (1).

                   Olive oil :                 refined            virgin

Phenols mg/L

    Hydroxytyrosol                   —                  63.5

    Tyrosol                               —                 24.4

    Vanillic acid                         —                   0.2

    Vanillin                                —                  0.5

    p-Coumaric acid                   —                  0.3

    Ligstroside derivatives           —              208.0

    Oleuropein derivatives           —             327.2

    Luteolin                               —                  3.1

    Apigenin                              —                  0.7

    Methoxyluteolin                    —                  0.6

    Total phenols                        —                629

Other minor compounds

    α-Tocopherol                       229               228

    Squalene                          2754              3671

    β-Sitosterol                       1438              1612

Fatty acids %

 Monounsaturated fatty acids         80.4              81.8

    SFA                                    14.5             14.0

    PUFA                                    5.2               3.9

The results of this study showed that the administration of virgin olive oil significantly reduced the oxidative markers of LDL cholesterol in plasma, while the intake of refined olive oil showed much lower reductions (1).

Refined olive oil studies

References______________________________________

(1) Elevated circulating LDL phenol levels in men who consumed virgin rather than refined olive oil are associated with less oxidation of plasma LDL.  -  De la Torre-Carbot K, Chávez-Servín JL, Jaúregui O, Castellote AI, Lamuela-Raventós RM, Nurmi T, Poulsen HE, Gaddi AV, Kaikkonen J, Zunft HF, Kiesewetter H, Fitó M, Covas MI, López-Sabater MC.  -  J Nutr. 2010 Mar;140(3):501-8. doi: 10.3945/jn.109.112912. Epub 2010 Jan 20.

Visioli F, Caruso D, Grande S, Bosisio R, Villa M, Galli G, Sirtori C, Galli C. Virgin Olive Oil Study (VOLOS): vasoprotective potential of extra virgin olive oil in mildly dyslipidemic patients. Eur J Nutr. 2005;44:121–7

Stoclet JC, Chataigneau T, Ndiaye M, Oak MH, El BJ, Chataigneau M, Schini-Kerth VB. Vascular protection by dietary polyphenols. Eur J Pharmacol. 2004;500:299–313.

Angerosa F, Dalessandro N, Konstantinou P, Digiacinto L. Gc-Ris evaluation of phenolic-compounds in virgin olive oil. J Agric Food Chem. 1995;43:1802–07.

Turner R, Etienne N, Alonso MG, de Pascual-Teresa S, Minihane AM, Weinberg PD, Rimbach G. Antioxidant and anti-atherogenic activities of olive oil phenolics. Int J Vitam Nutr Res. 2005;75:61–70

Per os administered refined olive oil and marine PUFA-rich oils reach the cornea: possible role on oxidative stress through caveolin-1 modulation.  -  Dutot M, Liang H, Martin C, Rousseau D, Grynberg A, Warnet JM, Rat P.  -  Nutr Metab (Lond). 2009 Nov 23;6:48. doi: 10.1186/1743-7075-6-48.