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.