Olive Oil and Health: What Science Actually Says About Health and Longevity
A quick note: this article is not medical advice. It summarises peer-reviewed research. For decisions about your own diet or health, talk to a doctor or registered dietitian.
Some claims about olive oil get repeated so often that we stop asking whether they're true. "It's good for the heart." "People here live to 90 on it." Some of this holds up under real scrutiny. Some of it doesn't. This article tries to separate the two — with studies, not slogans.
What the research actually shows
The most cited trial is PREDIMED, a Spanish clinical trial with more than 7,400 participants, published in the New England Journal of Medicine. People who followed a Mediterranean diet supplemented with extra virgin olive oil had roughly 30% fewer major cardiovascular events (heart attack, stroke, cardiovascular death) than those on a low-fat control diet, over a median of nearly five years.
A Harvard cohort study of more than 92,000 people followed for 28 years, published in the Journal of the American College of Cardiology, found something similar outside a clinical trial setting: the highest olive oil consumers had about a 19% lower risk of death than those who rarely or never consumed it — and replacing butter, margarine, or mayonnaise with olive oil was linked to up to a 34% lower death rate.
More recently, the same Harvard team linked daily olive oil intake (more than 7 g/day, roughly half a tablespoon) to a 28% lower risk of dementia-related death, in a study published in JAMA Network Open in 2024. It's observational — it shows an association, not proof of cause and effect — but it adds to a growing body of evidence pointing the same way.
Not all olive oil counts the same, scientifically
Here's the detail most articles skip: most of these benefits are tied specifically to extra virgin olive oil — not to any bottle labelled "olive oil."
The European Food Safety Authority (EFSA) officially recognises that olive oil polyphenols — compounds like hydroxytyrosol — help protect blood lipids from oxidative stress, provided the oil contains at least 5 mg of these compounds per 20 g (roughly one and a half tablespoons) consumed daily. It's one of the few food-specific health claims formally approved in the EU — and it only applies to high-quality oils, typically lightly processed extra virgin olive oils rich in polyphenols, the kind that comes from olives picked at the right moment and cold-extracted with care.
In other words: quality isn't a marketing detail here. It's literally what determines whether the science applies.
How much — and where the limits are
The studies showing benefits generally use quantities between 20 g and 50 g per day (one to four tablespoons), as part of a balanced diet — not a single spoonful, and not a substitute for other health basics.
Proportion matters: olive oil is still a fat, at around 900 kcal per 100 g. The benefits observed in these studies appear when olive oil replaces less healthy fats — butter, margarine, processed fats — within a Mediterranean-style dietary pattern, not when it's simply added on top of an already fat-heavy diet. The science is about substitution and overall pattern, not miracles.
And in Trás-os-Montes and Alto Douro?
This is one of the oldest olive-growing regions on the Iberian Peninsula, with centuries-old groves and microclimates that favour oils with high polyphenol profiles — exactly the characteristic the science above links to these benefits. It's no coincidence that several producers here invest in early harvest and cold extraction: that's what preserves the compounds the studies are talking about.
If you want to experience that difference for yourself — compare a young, peppery oil with a milder, riper one, see a mill in action, talk directly to the people who make it — the region's producers and olive oil tourism experiences are the place to start. Each producer sets their own availability and terms; tell us what you're looking for through the contact form or at info@azeiteanorte.com, and we'll help point you to the right producer and experience.
Trás-os-Montes olive oil doesn't need explaining. You taste it
Sources
Estruch, R. et al. (2018). "Primary Prevention of Cardiovascular Disease with a Mediterranean Diet Supplemented with Extra-Virgin Olive Oil or Nuts." New England Journal of Medicine, 378, e34.
Guasch-Ferré, M. et al. (2022). "Consumption of Olive Oil and Risk of Total and Cause-Specific Mortality Among U.S. Adults." Journal of the American College of Cardiology, 79(2), 101–112.
Tessier, A-J. et al. (2024). "Consumption of Olive Oil and Diet Quality and Risk of Dementia-Related Death." JAMA Network Open, 7(5).
European Commission (2012). Regulation (EU) No 432/2012 — health claim on olive oil polyphenols, based on the EFSA scientific opinion (2011).
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