Olive Oil

Olive Oil

Olive oil (in Hebrew “שמן זית”) is the most researched fat in human nutrition, and it sits at the base of the strongest nutritional evidence that exists for any dietary pattern — the Mediterranean diet. It is extracted from the fruit of the olive tree (Olea europaea) by mechanical pressing, and unlike most vegetable oils, which are extracted with chemical solvents and refined, virgin olive oil is essentially fruit juice — which is where its active compounds come from.

100 grams of olive oil provides 884 calories and 100 grams of fat, of which about 73% is oleic acid (monounsaturated), about 14% saturated fat and about 11% polyunsaturated. But the fat composition is not the whole story: about 1-2% of the oil consists of minor components — polyphenols, vitamin E and squalene — and these are what distinguish the different grades.

The difference between grades — why it matters

This is the most important practical difference, and it is often misunderstood:

• Extra virgin (Extra Virgin, EVOO): produced by mechanical cold pressing only, with acidity below 0.8% and no sensory defects. Almost all the polyphenols are concentrated here — 150-400 mg per kg and even more.
• Virgin: the same process, acidity up to 2%, lower sensory quality.
• Refined / “light” / “regular”: has undergone chemical or thermal refining that removes defects — and along with them almost all the polyphenols and most of the vitamin E. In terms of fatty acids it is similar, but the active components behind the research are gone.

Almost all the research on the benefits of olive oil was done on extra virgin. The label “light” refers to taste and color only — not to calories.

Research-based health benefits

• The PREDIMED study — the strongest evidence: this is one of the most important studies in modern nutrition — a randomized controlled trial in about 7,400 participants at high cardiovascular risk. The group assigned to a Mediterranean diet enriched with extra virgin olive oil (about 50 ml per day) showed about a 30% reduction in major cardiovascular events compared with the control group, which was advised to follow a low-fat diet. The study was republished in 2018 after correcting methodological flaws in the randomization at some centers, and the conclusions held. It is one of the few cases where a randomized trial — not just an observational study — supports a dietary recommendation.

• Hydroxytyrosol and LDL protection: the European Food Safety Authority (EFSA) approved a unique health claim: olive oil polyphenols protect LDL particles from oxidative damage. LDL oxidation is a key step in the formation of atherosclerotic plaque — an oxidized LDL particle is the one engulfed by macrophages, forming foam cells in the artery wall. The claim requires an intake of at least 5 mg of hydroxytyrosol and its derivatives per day, an amount found in about 20 grams (about two tablespoons) of high-quality extra virgin olive oil.

• Oleocanthal — natural ibuprofen: the peppery, burning sensation in the throat when tasting fresh extra virgin olive oil comes from oleocanthal. This compound inhibits the COX-1 and COX-2 enzymes — the same mechanism by which ibuprofen works, though at much lower strength. The burn in the throat is a genuine sensory indicator of high polyphenol content.

• Oleic acid and lipid profile: replacing saturated fat with oleic acid lowers LDL without harming HDL. Unlike polyunsaturated fats, oleic acid is relatively stable against oxidation thanks to its single double bond.

• Effect on blood pressure and endothelial function: studies show improved endothelium-dependent vasodilation and a moderate drop in systolic blood pressure with regular intake of high-polyphenol olive oil.

• Microbiome and inflammation: olive oil polyphenols largely reach the large intestine and serve as a substrate for gut bacteria, alongside a documented effect on inflammatory markers such as CRP and IL-6.

Downsides and health considerations

• Calorie density: a tablespoon of olive oil provides about 119 calories. It is the most calorie-dense food in the kitchen per gram, and it is very easy to pour twice as much as planned. “Healthy” is not a synonym for “unlimited” — in the PREDIMED study the daily amount was defined.

• Fraud and misrepresentation: olive oil is one of the most counterfeited products in the world. Tests carried out in various markets have found that a considerable share of oils labeled “extra virgin” do not meet the standard — usually because they were blended with refined oil or other cheap oils, or because aging downgraded them. Helpful signs: a dark glass bottle, a stated harvest date (not just an expiry date), a specific geographic origin, and a price that is not suspiciously low.

• Smoke point and heat sensitivity: the smoke point of extra virgin is about 190-210°C (374-410°F) — enough for home cooking, the oven and light frying, but lower than that of avocado oil or refined canola. More importantly: even below the smoke point, prolonged heating gradually breaks down the polyphenols. The practical rule — use good extra virgin cold, and save a simpler oil for deep frying.

• Sensitivity to light, heat and oxygen: olive oil oxidizes when exposed to light and air. Storing it in a clear bottle on the counter next to the stove is the most effective way to ruin it. Store it in a cool, dark place and use it within a few months of opening.

• Olive oil does not improve with age: unlike wine. Fresh oil from the latest harvest is always better; after about one to two years the polyphenol content drops significantly.

Nutrition facts (per tablespoon, 15 ml)

Choosing and practical use

What to look for on the label: “Extra Virgin,” a harvest date, a defined geographic origin (not “a blend of olive oils from the European Union”), and a dark glass bottle or tin.

A sensory test: high-quality extra virgin olive oil should be slightly bitter and burn in the throat. These are not defects — they are the sensory signature of polyphenols. A “smooth” oil without character is usually low in polyphenols.

Smart division of use: keep two oils — a high-quality (and more expensive) extra virgin for cold use: salads, drizzling on a finished dish, bread, hummus; and a simpler olive oil for cooking and frying. That way you don’t waste polyphenols on heat and don’t give them up on the plate.

A combination that improves absorption: olive oil significantly improves the absorption of carotenoids from vegetables — lycopene from tomatoes, beta-carotene from carrots and lutein from leafy greens. A vegetable salad without fat is a salad whose absorption of some of its components is impaired.

Summary

Extra virgin olive oil is one of the few foods whose recommendation is supported by a randomized controlled trial and not just by observation. Its value lies not only in oleic acid — which is also found in other oils — but in its polyphenols, which exist almost exclusively in the extra virgin grade and are destroyed by refining, heat and poor storage. Two tablespoons a day, cold, from a reliable source, is the best-supported use.