143 Virgin Olive Oil Benefits 11.4 Virgin olive oil, oxidative stress, and inflammation Metabolic syndrome is closely related to oxidative stress and inflammation. In healthy individuals, excessive free radical production is counteracted by antioxidants. In pathological conditions, however, there is an imbalance between antioxidants and free radicals favouring the latter, thus triggering cell and tissue damage. Virgin olive oil can contribute to alleviate oxidative stress and inflammation through its richness in antioxidants, such as tocopherol (vitamin E) and phenolic compounds, and its high monounsaturated fatty acid content. It is known that oleic acid decreases gene expression of inflammatory pathways and increases that of anti-inflammatory ones, and that virgin olive oil phenolic compounds decrease arachidonic acid derived inflammatory mediators such as prostaglandins and thromboxanes. Results from the LIPGENE study (a randomised European dietary intervention study with metabolic syndrome individuals) demonstrated that a monounsaturated fatty acid rich diet reduced postprandial inflammatory status and oxidative stress associated with metabolic syndrome development, with a decrease in oxidative stress biomarkers. In the PREDIMED study, a reduction in inflammatory biomarkers, such as C-reactive protein, interleukine-6, adhesion molecules, and cytokines, was observed in individuals following a Mediterranean diet supplemented with extra virgin olive oil. 11.5. Virgin olive oil and HDL profile improvement Reverse cholesterol transport is the process by which the HDL lipoprotein removes cholesterol from the arterial walls (a process known as cholesterol efflux) conveying it to the liver to be excreted. Low levels of HDL lipoprotein are one of the metabolic syndrome components related to an increase in cardiovascular risk. For cardiovascular health maintenance, not only the number of HDL particles, but also their functionality, are key factors for removing cholesterol from cells. Data from PREDIMED and EUROLIVE (a randomised European study concerning the effect of olive oil polyphenols on cardiovascular risk factors) studies have shown that a dietary enrichment with virgin olive oil: improves cholesterol efflux from cells, protect HDLs from oxidation (oxidation of HDL impairs its functionality by reducing its cholesterol efflux capacity), and increases the quantity of cholesterol transported by the HDLs. The latter two features were observed in a direct dose-dependent manner with the phenolic content of the virgin olive oil consumed. In addition, polyphenols from virgin olive oil increase the expression of cholesterol efflux-related genes. Finally, it has been reported that an olive oil-enriched diet increases HDL anti-inflammatory and antioxidant properties thus improving its protective effects regarding vascular endothelial damage. It protects LDL from oxidation, avoiding its accumulation in vascular walls and triggering the atherosclerosis process.
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