Why it matters

In 2005 a scientist tasting fresh-pressed oil in Sicily noticed a sting at the back of his throat that he knew from studying liquid ibuprofen. His team traced it to a compound they named oleocanthal. In lab tests it blocked the same COX-1 and COX-2 enzymes that ibuprofen blocks [1][2].

Oleocanthal has relatives, including oleacein, oleuropein and hydroxytyrosol, and together they make up the oil's polyphenols [5]. The European Union allows only one health claim for them on a label: they "contribute to the protection of blood lipids from oxidative stress." Even that claim is allowed only when an oil contains at least 5 mg of hydroxytyrosol and its derivatives per 20 g, about 250 mg/kg, and the label has to say the effect comes with 20 g a day [3][4][5].

By international definition, virgin olive oil comes from the fruit "solely by mechanical or other physical means," with no treatment beyond washing, decanting, centrifuging and filtering [6]. It doesn't improve with age. Oxygen, warmth and light slowly turn it rancid, and its antioxidants run down as they fight that process [7].

Green, early-harvest olives make oil higher in phenols, while riper fruit gives more oil but fewer phenols [8][9][10]. Speed matters too. In a study of 228 batches at industrial mills, oil from olives milled within 24 hours had about 243 mg/kg of phenols, while oil from olives left for a week or more had 144 mg/kg, a 41% drop. The fruity, bitter and pungent notes faded along with them [11].

In 2010 UC Davis bought "extra virgin" oils in California stores and found that 69% of the imported samples failed the IOC/USDA sensory standard, against 10% of the California samples. The faults were rancid, fusty and musty flavours [12][13]. In 2011 the five top-selling imported brands failed at a 73% rate [14]. These were mostly low-grade or old olive oils, not "fake" oils made from something else, and the tests are now more than a decade old [7].

Good extra virgin olive oil is fine for cooking. Depending on grade and freshness, olive oil smokes at somewhere between 347°F and 464°F. Its natural antioxidants hold up under heat, and some of its phenols carry over into the food [7].

A 500 ml bottle holds about 33 tablespoons. A $40 bottle (hypothetical), at the FDA's suggested 2 tablespoons a day [16], works out to about $2.40. The average American latte cost $5.60 in 2025 [17].