Is Olive Oil Good for You? What the Trials Show

Olive oil has better human-trial evidence than any other fat in the kitchen — good enough that Great Britain authorises a health claim for its polyphenols, the only authorised wording that names the oil itself. It is also pure fat, about 120 kcal in a tablespoon, and every benefit in the trials came from oil eaten as food within a diet, not swallowed neat as a shot. This page reports the record in full — the trials, the claims a bottle may lawfully carry, and the drinking question, answered honestly.

Everything below is the published literature, cited as it comes; the rest of the evidence section reads the neighbouring shelves the same way.

Plate I · IllustrationRecord

What is olive oil, nutritionally?

Fat, and effectively nothing else. The standard reference analysis (USDA FoodData Central) puts olive oil at 100 g of fat and 884 kcal per 100 g, which makes a level tablespoon of about 14 g roughly 120 kcal. The fatty-acid split is what sets it apart from most other everyday oils: about 73% monounsaturated — overwhelmingly oleic acid — against 13.8% saturated and 10.5% polyunsaturated. It carries meaningful vitamin E (14.4 mg per 100 g) and, in extra virgin oils, a phenolic fraction — hydroxytyrosol, tyrosol, oleocanthal, oleacein and their relatives — that varies enormously between oils and is largely stripped by refining.

The fat is what the big diet trials feed; the phenolic fraction is what the sharpest trial isolates — and what the polyphenols evidence page examines compound by compound.

What did EUROLIVE prove about the polyphenols?

That they do something measurable in humans, and that the effect follows the dose. EUROLIVE (Covas and colleagues, Annals of Internal Medicine, 2006) is the trial to know, because its design does what no diet trial can: it isolates one constituent. Two hundred healthy men at six centres in five countries took 25 ml of olive oil a day, three weeks per oil, from three oils alike in every respect except phenolic content — low (2.7 mg/kg), medium (164 mg/kg) and high (366 mg/kg). The design was crossover: every man consumed all three in randomised order with washouts between, so each served as his own control and differences between people cancelled out.

The result was a straight line. HDL cholesterol rose linearly with the phenolic dose, and oxidative-stress markers fell linearly as it climbed — oxidised LDL moving from a small rise on the low-phenolic oil to a clear fall on the high. Since fat and calories were identical across the arms, the difference belongs to the phenolics. The authors’ conclusion, verbatim: “Olive oil is more than a monounsaturated fat.” Its limits: three-week periods, self-reported background diet, and blood markers rather than heart attacks. It is the core human evidence behind the GB claim that names olive oil, below.

Fig. I · EUROLIVE, drawn to its doseDiagram

Covas and colleagues · Annals of Internal Medicine, 2006

Randomised crossover trial. 200 healthy men at six centres in five countries took 25 ml of olive oil a day, three weeks per oil, from three oils alike in every respect except phenolic content.

Every man consumed all three in randomised order, with washouts between — each served as his own control, and differences between people cancelled out.

Phenolic content of the three oils · mg/kg · linear axis from 0

2.7Low164Medium366High

The axis is drawn to scale: 2.7 sits almost at the origin, 164 a little under halfway to 366. The spacing is the trial’s, not a design choice.

The result was a straight line

HDL cholesterol

Rose linearly with the phenolic dose.

Oxidised LDL

Fell linearly as the dose climbed — from a small rise on the low-phenolic oil to a clear fall on the high.

Fat and calories were identical across the arms, so the difference belongs to the phenolics.

The authors’ conclusion, verbatim

“Olive oil is more than a monounsaturated fat.”

Its limits: three-week periods, self-reported background diet, and blood markers rather than heart attacks.

What happened to PREDIMED — and does it still count?

PREDIMED is the most famous olive-oil trial and one of nutrition science’s best stories about correction: a landmark, a real methods defect, a transparent repair — all three worth telling.

The landmark first. The trial assigned 7,447 Spanish adults aged 55 to 80 at high cardiovascular risk — but with no cardiovascular disease — to one of three diets: a Mediterranean diet supplemented with free extra-virgin olive oil (about a litre a week supplied to households), the same diet with mixed nuts, or a control diet of advice to reduce dietary fat. After a median of 4.8 years the trial was stopped early: major cardiovascular events — heart attack, stroke, cardiovascular death — were markedly less frequent in both Mediterranean arms. The 2013 report in the New England Journal of Medicine became one of the most cited papers in nutrition.

Then the defect. A statistical screen of baseline tables across thousands of published trials flagged PREDIMED’s as improbable, and the investigators went looking. What they found and disclosed: at some sites, household members had been enrolled and simply given their relative’s diet without randomisation; one of eleven sites had assigned an entire clinic at a time; another appeared to have used its randomisation tables inconsistently. About 1,588 of the 7,447 participants were affected.

Then the repair. On 13 June 2018 the journal retracted the 2013 paper — and published, the same day, a full re-analysis that does not rely on the assumption that everyone was randomised. The republished estimates are materially the same: a hazard ratio of 0.69 (95% CI 0.53 to 0.91) for the olive-oil arm against the low-fat-advice control, robust to excluding every affected participant. The language, though, was honestly softened — the incidence of events “was lower among those assigned” to the Mediterranean diets, not “the diet prevented”. That is a correction done well, and the trial still counts — for what it tests: a whole diet plus quarterly counselling against fairly weak advice. Even repaired, it cannot isolate the oil from the pattern it sat in.

What do the other diet trials show?

CORDIOPREV (Delgado-Lista and colleagues, The Lancet, 2022) asked the harder question: not who stays well, but what to feed people who are already ill. At a single centre in Córdoba, 1,002 patients with established coronary heart disease were randomised to a Mediterranean diet built around olive oil or to a low-fat diet, both delivered by a team of dietitians, for seven years. The Mediterranean arm had fewer major cardiovascular events — 87 against 111, a rate of 28.1 versus 37.7 per 1,000 person-years, with adjusted hazard ratios between 0.72 and 0.75. Two things belong beside that result: the effect was clear in men, with no difference found among the trial’s 175 women — too few to settle it — and the funders included two olive-oil-sector foundations alongside Spanish public money and the EU, a fact to weigh rather than a verdict.

The deflationary anchor is Cochrane’s 2019 review (Rees and colleagues): 30 randomised trials, 12,461 participants, and a conclusion of “still some uncertainty”, with the quality of evidence for modest benefits graded low or moderate. Read through Cochrane’s stricter lens, PREDIMED’s most robust surviving endpoint is stroke — hazard ratio 0.60, a drop from 24 to 14 strokes per 1,000, graded moderate quality — while its mortality effects rate only low-quality evidence of little or no difference. The structural point matters more than any number: a diet trial bundles food, counselling, enthusiasm and everything the new foods displace into one intervention — it can show a pattern works without saying which component did the work. EUROLIVE isolates a constituent for three weeks; PREDIMED follows hard outcomes for years; no trial yet does both.

Which olive oil health claims are authorised in the UK?

Four, by two different routes — and the difference between the routes is the whole point. The Great Britain nutrition and health claims register, the authoritative list for England, Scotland and Wales, authorises this wording: “Olive oil polyphenols contribute to the protection of blood lipids from oxidative stress.” The conditions are precise. The claim may be used only for olive oil containing at least 5 mg of hydroxytyrosol and its derivatives (the register’s examples: the oleuropein complex and tyrosol) per 20 g of oil — 250 mg/kg — and the consumer must be told that the benefit is obtained at a daily intake of 20 g. The scientific basis is EFSA’s 2011 opinion, and the human trial at its core is EUROLIVE.

The threshold has teeth. Refined olive oils lose most of their phenolics in processing, and plenty of ordinary extra virgin sits below 250 mg/kg, so whether any given bottle qualifies is a laboratory question, batch by batch — the territory of high-polyphenol olive oil and of reading an olive oil label properly. And the boundary is policed: in 2025 EFSA assessed an application to extend the family with an HDL-maintenance claim and rejected it — “the evidence provided is insufficient to establish a cause-and-effect relationship” (EFSA Journal 2025;23(5):e9372) — its third refusal of that extension. That is the first route: a claim that names olive oil, and is conditional on a laboratory figure the bottle has to earn.

The second route does not mention olives at all. The register also authorises three wordings about replacing saturated fat — “Replacing saturated fats in the diet with unsaturated fats contributes to the maintenance of normal blood cholesterol levels. Oleic acid is an unsaturated fat”, the same sentence phrased for monounsaturated and polyunsaturated fats generally, and a third that goes further: “Replacing saturated fats with unsaturated fats in the diet has been shown to lower/reduce blood cholesterol. High cholesterol is a risk factor in the development of coronary heart disease.” That third one is an Article 14(1)(a) reduction-of-disease-risk claim — the strongest category in the scheme, and one most foods never reach — and the register restricts it to fats and oils.

Olive oil qualifies for all three automatically. Their condition is that the food be high in unsaturated fatty acids, which the register defines as at least 70% of the fatty acids present, with unsaturated fat providing more than 20% of the food’s energy. Olive oil runs about 83.5% unsaturated, so it clears the bar without needing anything measured. But read what the claim actually says: it is a claim about replacing saturated fat, and it would sit just as lawfully on rapeseed or sunflower oil. It says nothing about olives. The polyphenol claim is the only authorised wording in Great Britain that is about olive oil specifically — which is why it is the one worth testing a bottle against.

And the general claims — the ones a shopper would expect to see — were all refused. “Olive oil consumption helps to maintain the health of the cardiovascular system” appears on the register three times, non-authorised each time. So does “Olive Oil promotes your heart health”. So does a claim that olive polyphenols contribute to a good HDL level, and one that olive leaf extract reduces the blood-glucose rise after meals. The pattern is consistent: the composition claims stand, the food claims do not.

For contrast: honey has no authorised claim at all — the same register’s eight honey entries are all non-authorised, and the honey evidence page tells that story.

Fig. II · What a bottle may lawfully sayDiagram

Great Britain nutrition and health claims register

The authoritative list for England, Scotland and Wales. An oil reaches an authorised claim by two different routes — by being named, and by its composition.

AuthorisedRoute one — the register names the oil

“Olive oil polyphenols contribute to the protection of blood lipids from oxidative stress.”

Qualifying oil

At least 5 mg of hydroxytyrosol and its derivatives per20 g of oil — 250 mg/kg. The register’s examples: the oleuropein complex and tyrosol.

What the consumer must be told

The benefit is obtained at a daily intake of 20 g of the oil — about a tablespoon and a half.

Scientific basis

EFSA’s 2011 opinion; the human trial at its core is EUROLIVE — Fig. I above.

The threshold has teeth: refined olive oils lose most of their phenolics in processing, plenty of ordinary extra virgin sits below 250 mg/kg, and whether any given bottle qualifies is a laboratory question, batch by batch.

AuthorisedRoute two — the oil qualifies on composition

“Replacing saturated fats in the diet with unsaturated fats contributes to the maintenance of normal blood cholesterol levels. Oleic acid is an unsaturated fat.”

“Replacing saturated fats with unsaturated fats in the diet contributes to the maintenance of normal blood cholesterol levels [MUFA and PUFA are unsaturated fats].”

“Replacing saturated fats with unsaturated fats in the diet has been shown to lower/reduce blood cholesterol. High cholesterol is a risk factor in the development of coronary heart disease.”

Qualifying food

Food high in unsaturated fatty acids: at least 70% of the fatty acids present derived from unsaturated fat, with unsaturated fat providing more than 20% of the food’s energy. Olive oil is about83.5% unsaturated, so it clears the threshold outright.

The third one is stronger

It is an Article 14(1)(a) reduction-of-disease-risk claim — the category most foods never reach — and the register restricts it: “The claim may only be used on fats and oils.”

What it is not

A claim about olive oil. It is a claim about replacing saturated fat, which olive oil happens to qualify to carry — and only where the replacing is actually done.

Rejected · 2025An application to extend the family

An HDL-maintenance claim

EFSA’s assessment: “the evidence provided is insufficient to establish a cause-and-effect relationship” — its third refusal of that extension.

For comparison, on the same register

Honey has no authorised claim at all — its eight entries are all non-authorised.

One claim names the oil. Three more are open to it for what it is made of. Every claim about olive oil as a food — heart health, cardiovascular health — was refused.

How much olive oil a day?

Every quantity in the evidence above lands in a narrow band, which is the most useful thing this page can tell you.

The regulator’s figure is 20 g a day — about a tablespoon and a half — the intake at which the polyphenol claim’s benefit is stated to be obtained. EUROLIVE administered 25 ml daily. The largest cohort study drew its top category at more than 7 g a day, half a tablespoon. MICOIL used 50 ml, the outlier and a pilot. PREDIMED supplied households with about a litre a week, which works out near 20 g a day per person if one person drinks it all and much less if a family shares it.

So: half a tablespoon a day is where the cohort evidence starts, and a tablespoon and a half is the regulator’s figure. Nothing in the record supports going higher, and the reason is arithmetic rather than caution — at 884 kcal per 100 g, 50 ml is roughly 400 kcal, and a benefit measured in oil that replaced other fats does not survive being added on top of them.

Fig. III · Every dose, on one axisDiagram

Five sections of this page name a quantity, in three different units. Converted to grams a day, they land closer together than they read.

>7 gCohort study — the top intake category

More than half a tablespoon a day. Stated in the abstract as “>0.5 tablespoon/day or >7 g/d”, and the lowest figure on this axis — about 62 kcal.

10 gThe substitution, not an intake

The weight of margarine, butter, mayonnaise or dairy fat that the same cohort swapped for the equivalent weight of olive oil. What was taken away is half the reading.

20 gThe GB register’s conditionRegulator

About a tablespoon and a half, roughly 175 kcal. The intake at which the polyphenol claim’s benefit is stated to be obtained, and the only figure here fixed in law rather than chosen by a trial.

25 ml ≈ 23 gEUROLIVE — three weeks

The trial that isolated the phenolics, at a dose a shot delivers — about 200 kcal.

50 ml ≈ 46 gMICOIL — twelve months

The outlier, and a pilot with no placebo arm. Roughly 400 kcal a day, which is the reason this end of the axis is not a target.

≈1 litre / weekPREDIMED — supplied to householdsNo bar drawn

Not a personal daily dose: it divides by however many people were in the house, so no bar is drawn. Near 20 g a day if one person has all of it, and much less if a family shares it.

025 g/day50

For scaleOlive oil is 884 kcal per 100 g — a level tablespoon, about 14 g, is roughly 120 kcal. In every study here that energy arrived inside a diet, in place of other fats.

What does the largest cohort study show — and what does it not?

The biggest observational study on this question is Guasch-Ferré and colleagues, published in the Journal of the American College of Cardiology in 2022. It followed 60,582 women in the Nurses’ Health Study and 31,801 men in the Health Professionals Follow-up Study, all free of cardiovascular disease and cancer at entry, from 1990 to 2018 — 28 years, 36,856 deaths, with diet assessed by questionnaire every four years.

Against people who never or rarely used olive oil, those in the highest category — more than 7 g a day — had a pooled hazard ratio for all-cause mortality of 0.81 (95% CI 0.78 to 0.84). Cause by cause: cardiovascular mortality 0.81 (0.75 to 0.87), cancer 0.83 (0.78 to 0.89), neurodegenerative disease 0.71 (0.64 to 0.78), respiratory disease 0.82 (0.72 to 0.93).

Then the two findings that matter more than any of those numbers.

What it was replacing decided the result. In the substitution analysis, swapping 10 g a day of margarine, butter, mayonnaise or dairy fat for the same amount of olive oil was associated with 8% to 34% lower mortality. That is the effect: a substitution, not an addition.

And against other vegetable oils, the association disappeared. In the authors’ words, no significant associations were observed when olive oil was compared with other vegetable oils combined. A cohort this large, finding nothing, is a real result — and it lands in exactly the same place the register does. Great Britain’s authorised claims about unsaturated fat are claims about replacing saturated fat, which any high-unsaturated oil may carry; the only authorised wording that names olive oil specifically is the polyphenol one. The regulator and the largest cohort study, working from different evidence, drew the same line: most of what olive oil does, in the numbers we have, it does by not being butter.

This is observational, with everything that implies — people who cook with olive oil differ from people who do not, in income, in diet, in much else, and no adjustment removes all of it. It cannot establish cause. What it can do is agree or disagree with the trials, and on the substitution point it agrees.

Is drinking olive oil good for you?

The question the trials can answer is narrower than the question as asked. In every trial on this page, the oil was consumed as food within a diet: EUROLIVE administered 25 ml a day, MICOIL assigned 50 ml a day, PREDIMED supplied households with a litre a week. So the quantity a morning “shot” delivers — 20 to 25 ml — is a genuinely trial-tested daily amount. What has never been tested, in anything cited here, is the shot as such: neat oil on an empty stomach against the same oil in meals, or a shot added to an unchanged diet against no shot at all. The comparison the ritual implies has not been run.

What a shot certainly is, is energy. A tablespoon-sized shot is about 14 g of fat and roughly 120 kcal; EUROLIVE’s 25 ml comes to about 200 kcal. In the trials, that energy arrived inside a whole diet, taking the place of other fats and foods; poured on top of an unchanged diet, the calories are the only guaranteed effect. And what happens if you drink it every day? At trial doses the answer is above: three weeks shifted blood-lipid markers with the phenolic dose; years inside a counselled Mediterranean pattern meant fewer major events in high-risk adults. The GB claim’s own figure — 20 g a day, about a tablespoon and a half — attaches to qualifying oil in any dish at any hour. What heat does or does not do to it in the pan is a separate question, answered at cooking with extra virgin olive oil.

Does olive oil help memory and cognition?

One randomised pilot says perhaps — and a pilot is an invitation, not an answer. MICOIL (Tsolaki and colleagues, Journal of Alzheimer’s Disease, 2020) randomised adults with mild cognitive impairment to three arms — a Greek high-phenolic early-harvest extra virgin olive oil at 50 ml a day, a moderate-phenolic oil at the same dose, or Mediterranean-diet advice alone — for twelve months, with cognitive testing at both ends. Both oil groups outperformed the advice-only group on ADAS-cog and MMSE scores, the high-phenolic arm did best across almost all cognitive domains, and the advice-only group scored worse than or level with its own baseline.

The caveats are the usual ones for a pilot, and they are load-bearing: a small single trial, and no placebo arm — the comparison group took no oil at all, so participants knew where they stood. Findings like this are hypothesis-generating: they specify the larger, blinded trial someone should now run rather than delivering a result to rely on. The constituents that make an oil “high-phenolic” — and why early-harvest oils carry more of them — are laid out on the polyphenols page.

Who should be careful with olive oil?

Nobody has to avoid it the way infants must avoid honey; the cautions here are quieter, and there are two. The first is arithmetic: at 884 kcal per 100 g, no food in the kitchen is more energy-dense, and the trial benefits belong to oil that replaced part of a diet, not oil added to all of one. The second is context: the strongest results above were achieved under supervision — CORDIOPREV’s patients had coronary disease and rebuilt their diets with a hospital team of dietitians over seven years. Anyone managing a heart condition, diabetes or medication who wants to redesign their eating around these trials has a plan worth taking to their GP or a dietitian first.

So — is olive oil good for you?

Read as a whole, the record says this: olive oil is a pure fat with an unusually good trial history. Its phenolic fraction shifted blood-lipid markers dose-dependently in the one trial built to isolate it, and that finding survived Europe’s food regulator to become the only authorised wording in Great Britain that names olive oil at all — 5 mg per 20 g, 20 g a day, exactly worded. Three further claims are open to the oil, but only for being high in unsaturated fat, which is a fact about its fatty acids and not about olives; every general claim about olive oil as a food was refused. The whole-diet trials, one of them corrected in public and the better for it, consistently favour Mediterranean eating with olive oil at its centre, at low-to-moderate certainty, without being able to credit the oil alone. The largest cohort study, following 92,000 people for 28 years, found lower mortality at more than half a tablespoon a day — but only where the oil replaced butter, margarine, mayonnaise or dairy fat, and not when it was set against other vegetable oils. The drinking ritual borrows the trials’ doses while discarding the way they were consumed. The rest of the category — the compounds, the oils that carry them, the labels that show it — starts at the olive oil hub.