You’re standing in the supermarket, in front of the olive oil shelf. Ten bottles, ten promises. “Extra virgin.” “First press.” “Cold-extracted.” A bottle with a little Italian village on the label costs four euros; the one beside it, fifteen. And you think: does it actually make any difference? Is this health, or am I paying for a story?

It’s a fair question. And the answer is more nuanced than either the marketing or the sceptics would have you believe. Let’s tease it apart, calmly.

The study that was too convincing to finish

In Spain, one of the most famous nutrition studies ever ran its course: the PREDIMED study. And it’s a fascinating one.

More than 7,400 people at raised risk of cardiovascular disease were split into three groups. One group followed a Mediterranean diet with extra olive oil — free bottles, every week. The second followed that same diet with extra nuts. The third was given the standard “low-fat eating” advice. The study was planned to run for six years.

But after an average of 4.8 years, it was stopped early. Not because it was failing — precisely because it was working so clearly. The two Mediterranean groups had roughly 30% fewer heart attacks, strokes and deaths from cardiovascular disease than the control group. It would have been unethical to keep the control group on “the lesser diet” any longer.

Here comes the honesty that belongs with it. PREDIMED had to be retracted and re-published in 2018, because at some study sites people had not been allocated individually, but per household or per clinic — sometimes, in effect, per village. After a thorough re-analysis, the conclusion still stood: the Mediterranean diet with olive oil helped. But it wasn’t a perfect study, and you deserve to know that.

Olive oil isn’t a thing. It’s a spectrum.

Here lies the heart of the confusion. We say “olive oil” as though it were one product. But between those bottles on the shelf lies a world of difference.

Picture olives as grapes, and oil as wine. A fresh, cold-pressed extra virgin is like a wine that still carries the taste of the grape. A refined oil is like alcohol from which all the flavour has been boiled out: still fat, but the soul is gone.

That difference lives in the polyphenols — tiny plant compounds the olive makes to protect itself. In extra virgin olive oil they’re largely preserved. In refined or “ordinary” olive oil they’re mostly stripped out during processing.

And that’s no detail. A follow-up analysis within PREDIMED showed that it was specifically the extra virgin variety that was linked to less cardiovascular disease; ordinary olive oil, without those polyphenols, didn’t show the benefit. A large American observational study of more than 92,000 people, followed over 28 years, found that those who ate the most olive oil (just over half a tablespoon a day) had a 19% lower risk of dying from any cause.

Important: that last study is observational. That means it shows an association, not proof of cause. People who use a lot of olive oil often live more healthily in other ways too. The oil may be a sign of a healthy life, not only its engine. Fair is fair.

The pepper in your throat isn’t a coincidence

Have you ever tasted a sip of fresh extra virgin and felt a tingling, peppery bite at the back of your throat? Almost a little cough?

That’s not a flaw. That’s a compound called oleocanthal. And in 2005, researchers discovered something remarkable: that stinging sensation resembles what ibuprofen does in your throat — and oleocanthal turns out, in the laboratory, to block the same anti-inflammatory enzymes as ibuprofen (the COX enzymes). The discovery began, quite literally, with a scientist recognising the similarity in his own throat.

Lovely story. But let me temper it straight away, because this is where it’s often overblown. The amount is small: about 50 grams of extra virgin a day delivers some 10 mg of oleocanthal — comparable to a tenth of a light dose of ibuprofen. And some scientists question whether that effect carries through in your body as strongly as it does in a test tube. So olive oil is not a painkiller. But that peppery bite is a sign of a living, polyphenol-rich oil. The taste is, quite literally, a quality signal.

“You mustn’t cook with it” — is that true?

This is perhaps the most stubborn myth of all. You hear it everywhere: olive oil has a low smoke point, so keep it for cold use and fry with something else.

The science here is surprisingly reassuring. The smoke point of extra virgin sits around 190 to 210 °C. Most home cooking — stir-frying, braising, frying an egg — stays comfortably below 200 °C. And, more importantly: the smoke point turns out to be a poor predictor of how safe an oil is when heated. What really counts is oxidative stability: how well an oil holds its structure without forming harmful compounds. And there, extra virgin actually scores well, thanks to its mostly monounsaturated fats and those same protective polyphenols.

One caveat, because it belongs here: part of the strongest “olive oil is the most stable” research was funded by the olive oil industry itself. The direction of the evidence is solid and supported by independent research too, but you’re entitled to know where some claims come from.

So what’s the answer to your question — cold or hot? Both. You can cook with it perfectly well. But heat does break down some of the polyphenols and oleocanthal; research points to around 40% loss with vigorous frying. The practical solution is simple and rather lovely: cook freely with a decent olive oil, and keep a good, peppery extra virgin aside to drizzle over your dish after cooking. Raw over your salad, your soup, your roasted vegetables. That way you get both the flavour and the compounds that cooking would have damaged.

Is there even real olive oil in that bottle?

And then the question that perhaps occupies you most. You’ll have seen the viral headline: “69% of olive oil is fake.” It comes from a 2010 report by the University of California, Davis.

But read the report carefully and that headline doesn’t hold. What they found was that 69% of imported “extra virgin” oil failed the taste test — too old, too oxidised, not the quality “extra virgin” ought to be. But in that same sample, the chemical tests found no adulteration: there was no cheap seed oil mixed in. “Failed the extra-virgin standard” is something very different from “fake.” On top of that, the report was part-funded by Californian olive oil producers — competitors of the imported oil. An interest worth weighing.

Later testing paints a calmer picture. The American food authority, the FDA, tested 88 samples and found no confirmed adulteration. And in 2025, the largest olive oil testing programme to date — 190 samples from the leading brands, together around 85% of the market — found not a single case of adulteration. Honestly stated: that programme was paid for by the industry body itself, the North American Olive Oil Association (NAOOA) — though it was independently designed and led by a Yale biostatistician, with blind testing in recognised laboratories. Only among a handful of tiny brands outside those 190 samples did adulteration still turn up; across the whole, it stayed under 1%.

So the honest conclusion is two-fold. Outright fraud — cutting olive oil with cheap seed oil — is rarer than the shouting headlines suggest. But quality fraud is real: an old, poorly stored or mediocre oil that nonetheless wears the “extra virgin” badge. Not poisoned. Just not what it promises. And it’s precisely that oil that lacks the polyphenols you were after in the first place.

So how do you choose?

Happily, there’s one reliable, official anchor. The European Union permits just one health claim for olive oil polyphenols: that they “contribute to the protection of blood lipids from oxidative stress.” A manufacturer may use that claim only if the oil contains at least 5 mg of hydroxytyrosol and related compounds per 20 grams. See that sentence on a bottle, and it’s a hard, regulated signal of quality.

And beyond that, in plain terms: choose a dark bottle (light breaks down the polyphenols), look for a harvest date and not just a best-before date, and trust your tongue — a good extra virgin is allowed to be bitter and peppery. Store it cool and dark, sealed. Oil that smells of old fat or cardboard is past its prime.

In closing

Olive oil is no miracle cure, and no swindle. It’s something more honest and more human: an ordinary product around which both real science and clever marketing have been built. The benefit doesn’t sit in one bottle, but in the pattern — in a way of eating and living where good oil is a small, daily gesture of care for yourself.

Perhaps that’s the deeper lesson. We so often go looking for that one magical thing that changes everything. Whereas real change is usually hidden in the small choices we repeat a hundred times.

Which small, daily choice are you already making — without even thinking about it any more — that quietly does you good?

Related reading

• Diets: What Really Works?
• Glutamine: Your Gut’s Favourite Food
• What Really Happens During a Hangover

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On withilhama.com I don’t give medical advice. Do you have health questions or a specific condition? Discuss it with your GP or specialist.

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Sources

• Estruch R, et al. Primary Prevention of Cardiovascular Disease with a Mediterranean Diet Supplemented with Extra-Virgin Olive Oil or Nuts (PREDIMED). New England Journal of Medicine (originally 2013, revised and re-published 2018, NEJMoa1800389).
• Guasch-Ferré M, et al. Olive oil intake and risk of cardiovascular disease and mortality in the PREDIMED Study. BMC Medicine. 2014;12:78.
• Guasch-Ferré M, et al. Consumption of Olive Oil and Risk of Total and Cause-Specific Mortality Among U.S. Adults. Journal of the American College of Cardiology (JACC). 2022. (Nurses’ Health Study & Health Professionals Follow-up Study; >92,000 participants, 28 years.)
• Beauchamp GK, Keast RSJ, Morel D, et al. Phytochemistry: ibuprofen-like activity in extra-virgin olive oil. Nature. 2005;437:45–46.
• Lozano-Castellón J, et al. Effect of heating on oleocanthal and polyphenols in extra virgin olive oil. Antioxidants. 2020. (On the decline of oleocanthal with heating.)
• De Alzaa F, Guillaume C, Ravetti L. Evaluation of Chemical and Physical Changes in Different Commercial Oils during Heating. Acta Scientific Nutritional Health. 2018. (Note: olive-oil-industry-affiliated research.)
• UC Davis Olive Center. Evaluation of Extra Virgin Olive Oil Sold in California. 2010/2011. (Sensory standard; no adulteration demonstrated.)
• FDA scientists. Study of economic adulteration of extra virgin olive oil. 2015. (88 samples; no confirmed adulteration, risk assessed as low.)
• Kyriakides TC (Yale School of Public Health), commissioned by the North American Olive Oil Association (NAOOA). 2024 Olive Oil Testing Program. Results published September 2025. (190 samples from leading brands, ~85% of the market; no adulteration demonstrated. Independently designed and led, blind testing in IOC-recognised laboratories. NAOOA = industry body.)