🧪 Oleic acid

Oleic acid is a monounsaturated fatty acid with 18 carbon atoms and one double bond, the main fatty acid of olive oil: in genuine olive oil it makes up 55 to 85% of all fatty acids. It melts at about 13 °C, so it is liquid at room temperature; its chemical name is cis-9-octadecenoic acid (C18H34O2).

In genuine olive oil, oleic acid has to make up 55 to 85% of all fatty acids. This range is set in the International Olive Council standard and in EU rules and helps to detect adulteration. According to USDA, 100 grams of olive oil contain about 71 grams of oleic acid, and extra virgin olive oil 67.8 grams. Classic high-linoleic sunflower oil has only 19.5 grams, while high-oleic sunflower oil has 82.6 grams.

Olives are not the only source of oleic acid. According to USDA, almonds contain 31.3 grams per 100 grams, salted butter 20 grams, avocado about 9 and egg 3.4 grams. FDA also mentions it in milk, cheese and meat.

Regulators speak cautiously about health benefits. In the EU it is permitted to state that replacing saturated fats with unsaturated fats helps maintain normal blood cholesterol levels, oleic acid being an unsaturated fat; such a claim may be used only on products in which at least 70% of the fatty acids are unsaturated. In 2018 the US Food and Drug Administration (FDA) allowed a qualified claim: about 20 grams a day of oils with at least 70% oleic acid, used in place of saturated fats, may reduce the risk of coronary heart disease, although the evidence is not conclusive.

Why it matters to you. The figure “acidity 0.8%” on extra virgin olive oil is not the oleic acid content but the share of free fatty acids, merely expressed as oleic acid. Oleic acid itself is bound in the fats of the oil and makes up 55–85% of the fatty acids.