Health

Olive oil is the primary source of fat in the Mediterranean diet which is associated with a low mortality for cardiovascular disease. A large body of knowledge exists providing evidence of the benefits of olive oil consumption on secondary end points for cardiovascular disease. On November 2004, the Federal Drug Administration (FDA) of the USA, permitted a claim on olive oil labels concerning: “the benefits on the risk of coronary heart disease of eating about 2 tablespoons (23 grams) of olive oil daily, due to the monounsaturated fat (MUFA) in olive oil”. Recently, results of large EPIC cohorts have reported an inverse relationship between olive oil consumption and coronary heart disease (CHD) mortality and incidence. An inverse relationship between olive oil consumption and stroke risk in women has been reported in the Three-City Study. The replacement of saturated fatty acids (SFA) by oils enriched in MUFA versus polyunsaturated fatty acids (PUFA) had similar effects on lowering total and low-density lipoproteins (LDL) cholesterol. The PUFA-enriched oil had a slight triglyceride lowering effect, and there was an increase in HDL cholesterol after MUFA consumption in some studies. There is, however, an issue in which MUFA consumption prevails over the PUFA one: the lipoprotein oxidation. Oleate-rich LDL are less susceptible against oxidation than linoleate-rich particles. This is due to the fact that PUFAs are the key substrate for lipid peroxidation whose propagation chain is going on via the double bonds of the fatty acid.

[María-Isabel Covas, Rafael de la Torre, Montserrat Fitó, (2014). Scientific evidence of the benefits of virgin olive oil for human health. Medicina Balear, 29(2), 39-46]

From several studies comparing the resistance of Low-Density Lipoprotein (LDL) to oxidation only in 2 of them did MUFA-rich diets not promote a higher resistance of LDL to oxidation than PUFA-rich ones. Oxidation of the lipid part, or directly of the apolipoprotein (apo) B, of the LDL leads to a change in the lipoprotein conformation by which the LDL is better able to enter into the monocyte/macrophage system of the arterial wall, and develop the atherosclerotic process. Oxidized LDL has been shown to be independently associated with 10-year coronary artery disease (CAD) events in the general population, and improved the reclassification capacity of Framingham-derived CAD risk functions. Phenolic compounds present in VOO have proven to be protective against LDL oxidation. On November 2011, the European Food Safety Authority (EFSA) released a claim concerning the benefits of the daily ingestion of olive oil rich in phenolic compounds, such as the virgin olive oil. The Panel considers that in order to bear the claim, 5 mg of OHTyr and its derivatives (e.g. oleuropein complex and Tyr) in olive oil should be consumed daily. These quantities, if provided by moderate amounts of olive oil, can be easily consumed in the context of a balanced diet.

[María-Isabel Covas, Rafael de la Torre, Montserrat Fitó, (2014). Scientific evidence of the benefits of virgin olive oil for human health. Medicina Balear, 29(2), 39-46]

The beneficial effects of the phenolic constituents in olive oil

There have been many reports on the lower incidence of cancer in animals and humans after consumption of olive oil. It was concluded that olive oil does not have the cancer-promoting potential of other fat types. However, additional studies will be required to confirm this hypothesis. Numerous studies have shown that these phenols are potent inhibitors of LDL oxidation in vitro. The in vivo oxidation of LDL is linked to the formation of atherosclerotic plaques, which are postulated to contribute to the development of coronary heart disease. Olive oil phenols have also been beneficially linked to processes that contributes to the pathogenesis of heart disease and cancer. In particular hydroxy-tyrosol, one of the major phenolic constituents in olive oil, has been reported to alone reduce the risk of coronary heart disease and atherosclerosis. It has also been postulated that hydroxy-tyrosol inhibits arachidonic acid lipoxygenase or inhibits platelet aggregation. It is presumed that hydroxy-tyrosol penetrates in cell membranes and consequently can inhibit the production of leukotriene B4 (LTB4) effectively from endogenous arachidonic acid.

[Tuck KL, Hayball PJ. Major phenolic compounds in olive oil: metabolism and health effects. J. Nutr. Biochem. (2002), 13(11): 636-644, doi: 10.1016/s0955-2863(02)00229-2. PMID: 12550060]

Cardiovascular Disease: There is a large body of evidence that explains the mechanisms underlying the prevention of coronary heart disease by Extra virgin olive oil (EVOO). EVOO is high in monounsaturated fatty acids, which may mediate the prevention and management of cardiovascular disease and associated risk factors through favorable effects on blood cholesterol levels and improvement of insulin sensitivity. A systematic review and meta-analysis of 27 randomized placebo-controlled clinical trials (1089 participants in total) compared olive oil with other high-MUFA oils (e.g. flax-seed oil) and showed better outcomes in low-density lipoprotein (LDL) oxidation, lipoprotein concentration, and LDL particle size with olive oil. People who live in Mediterranean countries have lower rates of mortality from heart disease, with high EVOO consumption thought to be a major contributing factor. The well-known PREDIMED study, a high quality, five-year, randomized controlled study, compared a Mediterranean diet supplemented with four tablespoons or more of EVOO with a reduced-fat diet. This resulted in a 30% reduction in cardiovascular disease and stroke in the Mediterranean diet and EVOO group. Researchers found increases of 10 g/day in EVOO intake (approximately 1/2 tablespoon) were associated with a 10% reduction in the risk of cardiovascular events. The bioactive biophenol-compounds in EVOO have powerful cardio-protective properties, by improving the inner lining of the heart and blood vessels, and helping to lower blood pressure and prevent atherosclerosis.

A systematic review and meta-analysis of randomized controlled trials suggested that specific biophenol compounds in olive oil improve cardiovascular risk factors, specifically oxidized LDL cholesterol and blood pressure. One study of over 840,000 people, found that those who ate the most olive oil were 9% less likely to have heart issues and 11% less likely to die early compared to those who ate the least olive oil. A 2020 Australian study in healthy participants with diverse backgrounds and dietary habits found that consuming four tablespoons of high-biophenol EVOO per day, compared to refined olive oil, can significantly reduce systolic blood pressure, with about 30% reduction. In a meta-analysis including three cohort studies, for each increase of 25 g of olive oil intake, the relative risk of stroke was reduced by 26%. Those that consumed the highest amounts of olive oil had a 41% lower risk of stroke. There is substantial evidence that dietary patterns high in EVOO improve cardiometabolic risk factors and reduce type 2 diabetes risk, likely due to its monounsaturated fat content and high amounts of biophenols. A systematic review and meta-analysis of cohort studies and intervention trials found that 15-20 g per day of EVOO could reduce the risk of type 2 diabetes by 13%. In comparison to a low-fat diet, a diet high in olive oil was also found to help normalize blood glucose in people who already had type 2 diabetes.

[Olive Wellness Institute, Extra Virgin Olive Oil Health and Nutrition Report, p.p. 21, https://olivewellnessinstitute.org/wp-content/uploads/2023/03/OWI-Health-and-Nutrition-Report-Web-version-1.pdf]

[Hatzis CM, Sifaki-Pistolla D, Kafatos AG. History of the Cretan cohort of the Seven Countries Study. Hormones, Athens, (2015), Apr-Jun, 14(2):326-9. doi: 10.14310/horm.2002.1587. PMID: 26158658]

Diabetes: There is substantial evidence that dietary patterns high in EVOO improve cardiometabolic risk factors and reduce type 2 diabetes risk, likely due to its monounsaturated fat content and high amounts of biophenols. A systematic review and meta-analysis of cohort studies and intervention trials found that 15-20 g per day of EVOO could reduce the risk of type 2 diabetes by 13%. In comparison to a low-fat diet, a diet high in olive oil was also found to help normalize blood glucose in people who already had type 2 diabetes. Another study of 25 healthy subjects found that 10 g of EVOO (compared to corn oil) improves the postprandial glycaemic control by lowering blood glucose. An unexpected finding was the improvement in the subjects’ lipid profiles, specifically the reduction in post prandial serum LDL cholesterol. In the PREDIMED intervention study, those assigned to a Mediterranean diet supplemented with EVOO had a significantly reduced risk of type 2 diabetes compared with the control reduced fat diet. Outside of the Mediterranean basin, in a large study of more than 140,000 US women followed for 22 years, total olive oil consumption, as well as substituting olive oil for other types of fats, was inversely associated with type 2 diabetes risk after adjustment for other dietary and lifestyle factors. The phenolic compounds present in EVOO may assist with glucose metabolism and improve insulin sensitivity and effectiveness. Reducing the risk of type 2 diabetes may be attributed to the antioxidant properties of EVOO. Oxidative stress appears to be implicated in ß-cell dysfunction, leading to type 2 diabetes. The bioactive components of olive oil are associated with reduced oxidative stress, improved endothelial function, lipid profile, insulin sensitivity, and glycaemic control.

Obesity And Weight Management: The specific contribution of olive oil to weight control was first suggested by results from Mediterranean diet studies, including the SUN study and confirmed in the PREDIMED study. Since then, further studies have found that an olive oil-rich diet can facilitate longer-lasting weight loss compared to a low-fat diet. A 2018 systematic review of randomized controlled trials (with minimum 12 weeks intervention) investigating the effect of olive oil on weight, body mass index and waist measurements in people with cardiovascular disease, found that diets enriched with olive oil reduced weight more than control diets. One explanation for the role of olive oil in weight reduction is due to its positive thermogenic effect on the body. The higher the thermogenesis, the more kilojoules or calories the body can burn, leading to weight reduction. The monounsaturated fats in olive oil increase the oxidation rate, inhibit body fat production (lipogenesis) and stimulate body fat breakdown (lipolysis). The high levels of phenols in EVOO also have an antioxidant effect that helps in decreasing oxidative stress, which is higher in those with obesity. Although high olive oil consumption may significantly increase energy intake, EVOO is generally not associated with higher body mass index or waist circumference measurements. Research suggests no significant differences in body mass index and weight circumference between high and low olive oil intakes. Instead, olive oil may modify the body composition of obese individuals by increasing lean body mass and decreasing the percentage of body fat. A study investigating the association between the prevalence of obesity and the types of dietary fat consumed in 168 countries found that countries with a higher monounsaturated fat consumption were strongly associated with low obesity prevalence. Similar results were reported from a six-year cohort study that monitored 613 participants on a diet with a high content of different types of fatty acids. This study found those that consumed sunflower oil had a higher incidence of weight gain than the group that consumed olive oil.

Οφέλη υγείας και διατροφικές επιδράσεις του ελαιόλαδου

Health benefits and nutritional applications of olive oil

[Frontiers in Pharmacology, (2021), Sec. Ethnopharmacology, Volume 12, https://doi.org/10.3389/fphar.2021.723040]

Due to large variations in EVOO phenol content, quality standards do not require a minimum phenol content to qualify an olive oil as “extra virgin”, nor do standards classify EVOO as low, medium, or high in total phenols. EVOO with a higher phenolic content will typically have a more robust flavor, including some bitterness, compared to EVOO with lower phenolic content. Phenolic content diminishes with time, and particularly when exposed to heat, light and oxygen. EVOO should be stored in a cool dark place and used within one to two months of opening a bottle or container. In a healthy balanced diet, the phenolic compounds in EVOO are not consumed in isolation; they are eaten as part of a complex food matrix and can synergistically function together with other compounds in the oil and the food that is consumed. The healthy fats in EVOO can enhance the availability and absorption of a variety of biophenols in the oil and other foods e.g. salad and vegetables.