Olive Oil

Olive oil is a vegetable oil obtained from olives, the fruits of the olive tree (Oleaeuropaea L.; family Oleaceae). Olive oil is obtained by pressing and crushing whole olives and separating the oil by physical or chemical processes. If olive oil is obtained “solely by mechanical or other physical means under conditions, particularly thermal conditions, that do not lead to alterations in the oil, and which have not undergone any treatment other than washing, decantation, centrifugation, and filtration” it is designated as virgin olive oil. This manufacturing technique allows the preservation and transfer of bioactive components, including polyphenols, from olives to olive oil ^[1].

The predominant component of olive oil is triacylglycerol (TGA; 98 – 99%). TGAs are a varied class of glycerol esters that have various fatty acid compositions. Mononuclear oleic acid (up to 83% w/w) is the main fatty acid found in olive oil TGAs. The remaining TGAs in olive oil are composed of palmitic acid, linoleic acid, stearic acid, and palmitoleic acid. Virgin olive oil has an abundance of lipophilic or amphiphilic microconstituents, such as phytosterols, squalene, tocopherols, phenolic compounds, derivatives of terpenic acid, etc. Phenolic compounds occur in the form of: phenolic acids or alcohols, oleuropein derivatives, lignans, and flavonoids. Polyphenol concentrations in olive oil can range from 50 to 1000 mg/kg. As a matter of fact, it depends on the agronomic factors, the ripeness of olives, as well as extraction technology, along with storage or packaging processes ^[2].

Virgin olive oils can be either classified as extra-virgin olive oil (EVOO) or as virgin olive oil. EVOO has ideal taste and odor, no organoleptic defects, and a free acidity level (expressed as oleic acid) of no more than 0.80 g per 100 g. It is the olive oil with the best quality. Virgin olive oil may contain a few minor sensory defects and has a free acidity level of no more than 2.0 g per 100 g ^[1].

Effect on Cardiovascular Diseases

In the 1990s, the Lyon Diet Heart Study, a prevention trial testing the protective effects of a Mediterranean diet (MD), indicated that increasing adherence to this type of diet reduced the risk of cardiovascular diseases. Since then, a large plethora of studies have been conducted to identify the specific diet or nutrient involved in cardiac protection. Due to this, the essential function that olive oil plays in the cardio-protective action of MD have become generally acknowledged. Indeed, olive oil (especially, virgin and extra virgin) has proved positive effects on many factors predisposing to cardiovascular diseases, including blood pressure, lipid profile, and endothelial function. Precisely because EVOO can improve lipid profile and lower blood pressure, which in turn lowers the risk of major cardiovascular events, it has been shown in the PREvención con DIeta MEDiterránea (PREDIMED) study to reduce the risk of cardiovascular disease and mortality in individuals at high cardiovascular risk. The high concentration of two phenolic components, oleuropein and hydroxytyrosol, in olive oil is primarily responsible for its preventive properties against cardiovascular and heart disease. These components have an antioxidant effect and lower platelet aggregation and monocyte adhesion while diminishing cardiotoxicity and coronary occlusion. Although both in vitro and in vivo studies are now being conducted to investigate these compounds, it is still unclear how effective they could be as nutraceuticals in the prevention of cardiovascular diseases ^[3].

The European Food Safety Authority granted approval in 2011 to some statements made by the Commission Regulation regarding the health advantages of bioactive chemicals found in food, such as EVOO phenols and, specifically, oleuropein and hydroxytyrosol, which play important roles for human health. The health benefits include preventing oxidative damage to low-density lipoprotein (LDL), maintaining normal blood levels of high-density lipoprotein (HDL) cholesterol, maintaining normal blood pressure, having anti-inflammatory properties, supporting the health of the upper respiratory tract, maintaining normal gastrointestinal tract function, and bolstering the body’s defenses against external agents. Furthermore, it has been demonstrated that oleuropein, the most prevalent polyphenol in EVOO, significantly increase the synthesis of lipopolysaccharide (LPS)-induced nitric oxide (NO), which is a bactericidal and cytostatic agent whose increased expression boosts macrophages’ functional activity ^[4].

Effect on Diabetes Mellitus

Diabetes mellitus (DM) is considered a challenging public health problem and one of the most common metabolic disorders, affecting millions of patients throughout the world. Studies confirmed that the protective effects were ascribable mostly to olive oil consumption. The strongest indication that olive oil may prevent type 2 diabetes comes from the PREDIMED study. In this follow-up trial, participants who had MD supplemented with EVOO presented a 40% lower incidence of diabetes than the control group, even though they did not have diabetes but were at high cardiovascular risk. Moreover, a multicentric parallel study of the PREDIMED found that taking virgin olive oil supplements with MD reduced body weight and enhanced glucose metabolism, two important parameters closely related to the onset of type 2 diabetes ^[3].

 

Effects on Gut Microbiota

Gut microbiota is a key factor in driving metabolic activities and is involved in the regulation of host immunity. Human metabolic and immunological problems are more likely to develop when the composition of the gut microbiota is altered. High-fat and high-sugar diets have the potential to modify the gut microbiota, which could lead to changes in some medical conditions associated with metabolic syndrome. Phenolic chemicals from olive oil can interact with the gut microbiota population in the intestines, potentially affecting the host’s immunological response, inflammation, and intestinal barrier oxidative state ^[1].

Healthier dietary patterns like the MD, which is rich in dietary fiber, beneficial fatty acids, and polyphenolic compounds, are associated with greater gut microbial diversity, increased abundance of beneficial bacteria, and reduced levels of inflammation and risk of chronic diseases. Notably, Ghosh et al investigated the effect of a MD on gut microbiota in 612 elderly European people over 12 months and found that adherence to the diet caused an increased abundance in several bacteria associated with improved cognition and was inversely associated with pro-inflammatory markers including C-reactive protein and IL-17. According to research on rodents and humans, EVOO consumption has a good impact on intestinal health and gut microbiota. Specifically, in humans, EVOO has prebiotic effects, promoting the growth of beneficial bacteria such as Lactobacillus and Bifidobacterium. In particular, 18 overweight/obese subjects received an MD supplemented with 40 g/day EVOO for three months, which led to noticeably higher levels of lactic acid bacteria than baseline. The ability of EVOO to act as both a prebiotic, stimulating the growth of beneficial bacteria, and an antibacterial, suppressing the growth of pathogenic bacteria, is likely attributable to the array of phenolic compounds EVOO contains. Approximately 90 – 95% of ingested phenolic compounds escape digestion in the small intestine and reach the colon, where they are catabolized into bioactive secondary structures, metabolites of their respective parent phenolic compounds that have been transformed by resident microbiota and can modify the composition of the gut microbiota ^[5].

 

Effect on Cognitive Health

Alzheimer disease (AD) is characterized by progressive memory loss and cognitive decline and, pathologically, by the deposition of Aβ plaques and accumulation of hyperphosphorylated tau proteins. EVOO, particularly the EVOO secoiridoid oleocanthal, was shown in multiple rodent trials to help prevent AD and to slow its progression. Researchers assessing the effect of chronic supplementation of EVOO on tau metabolism and synaptic function in transgenic mice overexpressing human tau found an increase in complexin 1, a presynaptic neuronal protein, and a notable decrease in tau oligomers in mice fed EVOO, resulting in enhanced short-term plasticity and memory. In a previous study, the same authors fed a 6-month EVOO diet to triple transgenic mice that developed amyloid plaques and neurofibrillary tangles and possessed three mutant disease genes linked to AD (PS1M146V, tauP301L, and APPSwe). This led to a significant decrease in Aβ peptides and a decrease in tau neuropathology due to the activation of autophagy mechanisms ^[5].

 

References

1. Isaakidis A, Maghariki J, Carvalho-Barros S, Gomes AM, Correia M. Is There More to Olive Oil than Healthy Lipids? Nutrients. 2023 [Cited 2024 September 13]; 15: 1-44. Available form: https://www.mdpi.com/2072-6643/15/16/3625
2. Gorzynik-Debicka M, Przychodzen P, Cappello F, Kuban-Jankowska A, Marino Gammazza A, Knap N, et al. Potential Health Benefits of Olive Oil and Plant Polyphenols. International Journal of Molecular Sciences. 2018 [Cited 2024 September 13]; 19: 1-13. Available form: https://www.mdpi.com/1422-0067/19/3/686
3. De Santis S, Cariello M, Piccinin E, Sabbà C, Moschetta A. Extra Virgin Olive Oil: Lesson from Nutrigenomics. Nutrients. 2019 [Cited 2024 September 26]; 11: 2085. Available form: https://www.mdpi.com/2072-6643/11/9/2085
4. Romani A, Ieri F, Urciuoli S, Noce A, Marrone G, Nediani C, Bernini R. Health Effects of Phenolic Compounds Found in Extra-Virgin Olive Oil, By-Products, and Leaf of Olea europaea L. Nutrients. 2019 [Cited 2024 September 30]; 11: 1-33. Available form: https://www.mdpi.com/2072-6643/11/8/1776
5. Millman J, Okamoto S, Teruya T, Uema T, Ikematsu S, Shimabukuro M, Masuzaki H. Extra-virgin olive oil and the gut-brain axis: influence on gut microbiota, mucosal immunity, and cardiometabolic and cognitive health. Nutrition Reviews. 2021 [Cited 2024 September 30]; 79: 1362-74. Available form: https://academic.oup.com/nutritionreviews/article/79/12/1362/6133931?login=false