Compendium of the most significant studies with reference to properties, intake, effects.

Abenavoli L, Milanović M, Milić N, Luzza F, Giuffrè AM. Olive oil antioxidants and non-alcoholic fatty liver disease. Expert Rev Gastroenterol Hepatol. 2019 Aug;13(8):739-749. doi: 10.1080/17474124.2019.1634544. 

Abstract. Introduction: Non-alcoholic fatty liver disease (NAFLD) is estimated to affect 25% of adult people worldwide. Nowadays, there is no definite treatment for NAFLD. International guidelines define an approach based on lifestyle changes, included a health alimentary regimen. The Mediterranean diet (MD) represents the gold standard in preventive medicine, probably due to the harmonic combination of many elements with antioxidant and anti-inflammatory properties. Its prescription is also recommended in patients with NAFLD. Olive oil, as part of MD, is associated with benefits on human health especially regarding the cardiovascular system, obesity, diabetes and related metabolic disorders. Areas covered: An overview of the beneficial effects of olive oil in the prevention and treatment of NAFLD is given. Expert opinion: A large body of evidence emphasizes that olive oil, used as primary source of fat in MD, may play a crucial role in the health benefits of NAFLD patients. However, there are still scarce clinical data that evaluate the direct effect of olive oil in human with NAFLD.

Karimi Z, Behnammoghadam M, Rafiei H, Abdi N, Zoladl M, Talebianpoor MS, Arya A, Khastavaneh M. Impact of olive oil and honey on healing of diabetic foot: a randomized controlled trial. Clin Cosmet Investig Dermatol. 2019 May 9;12:347-354. doi: 10.2147/CCID.S198577. 

Abstract. Background: This study aimed 1) to examine the impact of honey on diabetic foot; 2) to examine the effect of olive oil on diabetic foot; and 3) to compare the impact of honey and olive oil in the healing of diabetic foot. Methods: In this randomized controlled trial, 45 patients took part. Patients were randomly assigned to three groups. In the honey group, the wound was dressed using gauzes with honey daily for 1 month. In the olive oil group, the wound was dressed using gauzes with olive oil (4 mL) daily for 1 month. Patients in the control group received usual dressing. Wounds were assessed before and after intervention using the Wagner scoring system and the checklist of diabetic foot healing (where a higher score indicates better wound healing). Results: Demographic characteristics of patients in the three groups were similar. Mean scores of tissue around the wound, wound grade, wound drainage, and wound healing were similar before intervention in all three groups. After intervention, means score of tissue around the wound, wound grade, wound drainage, and wound healing were significantly higher in patients in the honey and olive oil groups compared to patients in the control group. Conclusion: The results of this study reveal that honey is as effective as olive oil in the treatment of diabetic foot. Given the few studies on this topic, further investigation is needed.

Drehmer E , Navarro-Moreno MÁ , Carrera S , Villar VM , Moreno ML . Oxygenic metabolism in nutritional obesity induced by olive oil. The influence of vitamin C. Food Funct. 2019 Jun 19;10(6):3567-3580. doi: 10.1039/c8fo02550a.

Abstract. Obesity is a medical and sociological problem of great importance due to the high percentage of people affected and the important health consequences that it involves. Most cases of obesity are related to an inadequate diet, rich in fats, which could lead to changes in the patient's oxygenic metabolism. That is why this study has been proposed to evaluate how some aspects of oxygenic metabolism are affected in a nutritional experimental model, with a controlled hyperlipidic liquid diet based on olive oil, and the effect of the antioxidant vitamin C on these conditions. Wistar rats were divided into four groups which received a control and hyperlipidic liquid diet for 30 days, with or without a vitamin C supplement (CO, COC, HO and HOC). First of all the body and fat tissue development was measured in the four groups. Our results showed that the excessive intake of nutritional and healthy fat such as olive oil did not prevent the appearance of obesity and the supplementation with vitamin C did not have a protective effect on body and fat development. The study of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) in total liver, liver cytosol, abdominal white fat, brown fat and blood cells showed that vitamin C could have different selectivities and affinities for different enzymes and compartments/tissues of the body. Finally, the effect of vitamin C on various metabolic parameters (glucose, pyruvate, lactate, LDH, ATP, acetoacetate and beta-hydroxybutyrate) provided positive protection against oxidative stress especially under hyperlipidic conditions. All things considered, the present study concludes that vitamin C treatment could protect Wistar rats from the oxidative stress impairment induced by obesity generated by an excessive intake of fats.

Pedan V, Popp M, Rohn S, Nyfeler M, Bongartz A. Characterization of Phenolic Compounds and Their Contribution to Sensory Properties of Olive Oil. Molecules. 2019 May 28;24(11):2041. doi: 10.3390/molecules24112041. 

Abstract. Olive oil is not only known for its pungent, bitter, and fruity taste, but also for its health potential, which is often hypothesized to depend on its phenolic compounds. One hundred extra virgin olive oil samples (monocultivaric as well as blends of varieties) were assessed with regard to their sensory properties and phenolic compound composition. Nineteen phenolic compounds have been determined and correlated with sensory data. In all olive oil samples, oleocanthal and oleacein were the most abundant phenolic compounds, with average amounts of 77.9 mg/kg and 41.8 mg/kg, respectively. The highest correlation coefficient between a sensory descriptor and the phenolic compounds was found for the bitter taste sensation and the total phenolic content with r = 0.72 and in particular, for 3,4-DHPEA-EA, with r = 0.57. Intensity plots were assessed for the three main sensory descriptors fruitiness, bitterness, pungency, and for the quality factor harmony, which is associated with the degree of ripeness aroma of olive oil. Positive correlations for the aroma descriptors freshly cut grass, leaves, and nuts, and the phenolic compounds were especially observed for oleoside 11-methylester and vanillic acid. The present study provides a comprehensive database of phenolic compounds in olive oils from six different varieties and seven countries.

Gonzalo-Gobernado R, Ayuso MI, Sansone L, Bernal-Jiménez JJ, Ramos-Herrero VD, Sánchez-García E, Ramos TL, Abia R, Muriana FJG, Bermúdez B, Montaner J. Neuroprotective Effects of Diets Containing Olive Oil and DHA/EPA in a Mouse Model of Cerebral Ischemia. Nutrients. 2019 May 18;11(5):1109. doi: 10.3390/nu11051109.

Abstract. Stroke is one of the leading causes of death worldwide and while there is increasing evidence that a Mediterranean diet might decrease the risk of a stroke, the effects of dietary fat composition on stroke outcomes have not been fully explored. We hypothesize that the brain damage provoked by a stroke would be different depending on the source of dietary fat. To test this, male C57BL/6J mice were fed for 4 weeks with a standard low-fat diet (LFD), a high-fat diet (HFD) rich in saturated fatty acids (HFD-SFA), an HFD containing monounsaturated fatty acids (MUFAs) from olive oil (HFD-OO), or an HFD containing MUFAs from olive oil plus polyunsaturated fatty acids (PUFAs) docosahexaenoic acid/eicosapentaenoic acid (DHA/EPA) (HFD-OO-ω3). These mice were then subjected to transient middle cerebral artery occlusion (tMCAo). Behavioural tests and histological analyses were performed 24 and/or 48 h after tMCAo in order to elucidate the impact of these diets with different fatty acid profiles on the ischemic lesion and on neurological functions. Mice fed with HFD-OO-ω3 displayed better histological outcomes after cerebral ischemia than mice that received an HFD-SFA or LFD. Furthermore, PUFA- and MUFA-enriched diets improved the motor function and neurological performance of ischemic mice relative to those fed with an LFD or HFD-SFA. These findings support the use of DHA/EPA-omega-3-fatty acid supplementation and olive oil as dietary source of MUFAs in order to reduce the damage and protect the brain when a stroke occurs.

Olive oil (Olea europaea – family Oleaceae)

Description

Olive oil is a plant-derived edible fat obtained exclusively from the mechanical pressing of olives, the fruits of Olea europaea. It is a central component of the Mediterranean diet, valued for both its nutritional profile and culinary versatility. Oil quality is influenced by multiple factors, including olive cultivar, degree of fruit ripeness, environmental conditions, and extraction techniques.

Production relies on mechanical processes that separate the lipid fraction from the olive pulp without the use of chemical solvents. Based on chemical and sensory parameters, olive oil is classified into several categories, including extra virgin olive oil, virgin olive oil, and refined olive oil. Extra virgin olive oil is distinguished by very low free acidity and a well-preserved aromatic profile.

From a nutritional perspective, olive oil consists predominantly of monounsaturated fatty acids, mainly oleic acid, which is associated with favorable effects on blood lipid profiles. It also contains phenolic compounds, tocopherols (vitamin E), and other minor constituents that contribute to oxidative stability and antioxidant activity. Regular consumption in appropriate amounts is consistent with a balanced diet focused on fat quality.

Classification

Raw material and product characteristics

Indicative average nutritional values per 100 g

Average indicative values referring to olive oil. Natural variability may occur depending on cultivar and degree of refining.

Note on nutritional use of the bioactive compounds present

Olive oil provides oleic acid, which contributes to the maintenance of normal blood cholesterol levels when replacing saturated fats. Olive oil polyphenols exhibit antioxidant properties and help protect blood lipids from oxidative stress. Vitamin E supports cellular protection against oxidative damage. Using olive oil raw helps preserve its bioactive compounds, enhancing both nutritional and sensory quality.

Industrial Production Process

The production of olive oil, including extra virgin, virgin, and refined olive oil, involves a series of processes to extract the oil from olives. The quality and type of olive oil depend on various factors such as the extraction method, the type of olives used, and the degree of processing. 

• Olive harvesting. Olives are harvested either by hand or using mechanical means to avoid damaging the fruit.
• Washing. The harvested olives are washed with water to remove impurities and residues of leaves or soil.
• Crushing. The olives, including pits, are crushed to break the cells and facilitate the release of the oil.
• Malaxation. The resulting olive paste is slowly mixed to allow the small droplets of oil to coalesce into a more easily separable oil phase.
• Extraction. The oil is separated from the paste mainly through centrifugation methods. Extra virgin olive oil is extracted cold, without the use of chemical solvents or high temperatures, to preserve its qualities.
• Decanting, filtering, and refining. The extracted oil may be left to decant to remove solid residues, filtered for clarity, and for some types of oil, like refined olive oil, further processed to remove imperfections.
• Bottling. The oil is bottled in containers that protect it from light and heat to preserve its properties.

Considerations

Olive oil is valued for its versatility and cardiovascular health benefits, thanks to its high content of monounsaturated fats which can help reduce bad (LDL) cholesterol and increase good (HDL) cholesterol.

Culinary Use Ideal for medium and high-temperature cooking, such as sautéing and frying, as it has a higher smoke point than extra virgin olive oil. It is also great for dressing salads and preparing sauces.

Health Benefits Contributes to heart health, supports cholesterol management, and has anti-inflammatory properties.

Storage Should be stored in an airtight container in a cool, dry place, away from light and heat to preserve its quality.

• virgin
• extra virgin

Studies

Medical

In cosmetic formulations for body care, the term 'Olea europaea oil unsaponifiables' indicates a non-saponifiable part of olive oil that is included as an emollient agent. The anti-inflammatory and antioxidant characteristics of the olive make this compound particularly effective, due to the presence of vitamins K and E, in counteracting skin dryness and in helping to relax the horny state, creating an anti-ageing effect. It is also useful in sunscreen products to protect the skin from UV radiation as the carotenoids contained in the oil have the ability to create a protective screen.

Olive oil studies

(1) Farnetti S, Malandrino N, Luciani D, Gasbarrini G, Capristo E. Food fried in extra-virgin olive oil improves postprandial insulin response in obese, insulin-resistant women. J Med Food. 2011 Mar;14(3):316-21. doi: 10.1089/jmf.2009.0264. 

Abstract. The benefits of low glycemic load (GL) diets on clinical outcome in several metabolic and cardiovascular diseases have extensively been demonstrated. The GL of a meal can be affected by modulating the bioavailability of carbohydrates or by changing food preparation. We investigated the effect on plasma glucose and insulin response in lean and obese women of adding raw or fried extra-virgin olive oil to a carbohydrate-containing meal. After an overnight fast, 12 obese insulin-resistant women (body mass index [BMI], 32.8 ± 2.2 kg/m(2)) and five lean subjects (BMI, 22.2 ± 1.2 kg/m(2)) were randomly assigned to receive two different meals (designated A and B). Meal A was composed of 60 g of pasta made from wheat flour and 150 g of grilled courgettes with 25 g of uncooked oil. Meal B included 15 g of oil in the 150 g of deep-fried courgettes and 10 g of oil in the 60 g of stir-fried pasta. Both meals included 150 g of apple. Blood samples were collected at baseline and every 30 minutes over a 3-hour post-meal period and were tested for levels of glucose, insulin, C-peptide, and triglycerides. The area under the curve (AUC) values were calculated. In obese women the AUCs for C-peptide were significantly higher after meal A than after meal B at 120 minutes (W [Wilcoxon sign rank test] = 27.5, P = .0020), 150 minutes (W = 26.5, P = .0039), and 180 minutes (W = 26.5, P = .0039). No differences were found in lean subjects. This study demonstrated that in obese, insulin-resistant women, food fried in extra-virgin olive oil significantly reduced both insulin and C-peptide responses after a meal.

 Damasceno NR, Pérez-Heras A, Serra M, Cofán M, Sala-Vila A, Salas-Salvadó J, Ros E. Crossover study of diets enriched with virgin olive oil, walnuts or almonds. Effects on lipids and other cardiovascular risk markers. Nutr Metab Cardiovasc Dis. 2011 Jun;21 Suppl 1:S14-20. doi: 10.1016/j.numecd.2010.12.006.

(2) Mateos R, Pereira-Caro G, Bacon JR, Bongaerts R, Sarriá B, Bravo L, Kroon PA. Anticancer activity of olive oil hydroxytyrosyl acetate in human adenocarcinoma Caco-2 cells. J Agric Food Chem. 2013 Apr 3;61(13):3264-9. doi: 10.1021/jf305158q.

Abstract. The anticancer activity of hydroxytyrosyl acetate (HTy-Ac) has been studied in human colon adenocarcinoma cells. Gene expression of proteins involved in cell cycle (p21, p53, cyclin B1, and cyclin G2) and programmed cell death (BNIP3, BNIP3L, PDCD4, and ATF3), as well as phase I and phase II detoxifying enzymes CYPA1 and UGT1A10, were evaluated by reverse transcription polymerase chain reaction after 24 h of exposure of Caco-2/TC7 cells to 5, 10, and 50 μM of HTy-Ac. The results show that HTy-Ac inhibited cell proliferation and arrested cell cycle by enhancing p21 and CCNG2 and lowering CCNB1 protein expression. HTy-Ac also affected the transcription of genes involved in apoptosis up-regulating of BNIP3, BNIP3L, PDCD4, and ATF3 and activating caspase-3. In addition, HTy-Ac also up-regulated xenobiotic metabolizing enzymes CYP1A1 and UGT1A10, thus enhancing carcinogen detoxification. In conclusion, these results highlight that HTy-Ac has the potential to modulate biomarkers involved in colon cancer.

(3) Martín-Peláez S, Covas MI, Fitó M, Kušar A, Pravst I. Health effects of olive oil polyphenols: recent advances and possibilities for the use of health claims. Mol Nutr Food Res. 2013 May;57(5):760-71. doi: 10.1002/mnfr.201200421.