Extra-virgin olive oil (EVOO) is the most comprehensively studied single food in nutritional science — with its health benefits attributed to its high oleic acid content (a monounsaturated fatty acid reducing LDL oxidation and promoting anti-inflammatory gene expression), its extraordinarily rich polyphenol content (particularly oleocanthal, which inhibits COX-1 and COX-2 enzymes in a manner similar to ibuprofen at culinary doses, and oleuropein), and its combination of fat-soluble vitamins and antioxidants that make it the dominant contributor to the Mediterranean diet's cardiovascular benefits.
Role
Olive oil's cardiovascular protection is among the most robustly documented food-health relationships in all of nutritional science — with the PREDIMED trial providing the strongest evidence (30% reduction in cardiovascular events with high EVOO consumption) — yet is routinely undermined in practice by the substitution of cheaper, lower-quality olive oils (refined, not extra-virgin, lacking polyphenols) or by concerns about its caloric density that miss the point that its health benefits are derived from fat-soluble polyphenols rather than its caloric content. The person who avoids olive oil for caloric reasons while using inflammatory refined seed oils is making one of the most consequential food substitutions available in the wrong direction.