Olive Oil Every Day: What the Evidence Shows

Whether countries that consume more olive oil live longer is something we examined in our country comparison – with a sober result: at national level the link is weak. The more interesting question is a different one: what happens to individual people who eat olive oil every day? For that we have large cohort studies spanning decades and one of the best-known nutrition trials ever run. This article summarises what they show – and what follows from it for everyday cooking.

The Harvard cohorts: 92,383 people, 28 years

The key single study appeared in 2022 in the Journal of the American College of Cardiology. A team led by Marta Guasch-Ferré analysed two large US cohorts: 60,582 women from the Nurses' Health Study and 31,801 men from the Health Professionals Follow-up Study, followed from 1990 to 2018. Nearly 37,000 participants died during that period. Every four years they reported what they ate.

Compared with people who never or rarely used olive oil, those consuming more than half a tablespoon a day (over 7 grams) showed the following risks:

Cause of death	Risk (hazard ratio)	Difference
All causes	0.81	19 % lower
Cardiovascular disease	0.81	19 % lower
Cancer	0.83	17 % lower
Neurodegenerative disease	0.71	29 % lower
Respiratory disease	0.82	18 % lower

The threshold is striking: half a tablespoon a day was already enough to fall into the most favourable group. This was not about large quantities, but about regularity.

The decisive point: olive oil replaces something

The same study calculated what happens when 10 grams a day of other fats are replaced by olive oil:

instead of margarine: 13 % lower mortality risk
instead of butter: 14 % lower
instead of mayonnaise: 19 % lower
instead of dairy fat: 13 % lower
instead of other vegetable oils: no significant difference

That is the most important line in the whole paper. The advantage shows up above all against animal and heavily processed fats – not against other good vegetable oils. Spooning olive oil on top of an unchanged diet makes no sense in this logic; it is meant to replace something.

Dementia: the 2024 study

In 2024 a team led by Anne-Julie Tessier (Harvard) examined the same cohorts with a focus on dementia and published the results in JAMA Network Open. Among 92,383 adults over 28 years, 4,571 died of dementia. Those consuming more than 7 grams of olive oil a day had a 28 percent lower risk of dying from dementia than those who never or rarely used it – irrespective of overall diet quality. The finding held after the researchers additionally adjusted for APOE ε4, the main genetic risk factor for Alzheimer's disease.

PREDIMED: the randomised trial

Cohort studies only observe. The Spanish PREDIMED trial, by contrast, assigned: 7,447 people aged 55 to 80 at high cardiovascular risk were randomly allocated to one of three diets – a Mediterranean diet with added extra virgin olive oil, a Mediterranean diet with nuts, or a reduced-fat control diet. After a median of 4.8 years, the risk of heart attack, stroke or cardiovascular death in the olive oil group carried a hazard ratio of 0.69 – around 31 percent lower than in the control group. The trial was published in 2013, retracted because of randomisation problems, and republished with a corrected analysis in the New England Journal of Medicine in 2018; the core finding stood.

Important: participants received around one litre of extra virgin olive oil per week for their household – far more than the 7 grams of the cohort studies. And what was tested was an entire dietary pattern, not olive oil alone.

What these studies do not show

Observation is not causation: people who use olive oil smoke less, move more and eat more vegetables. Studies adjust for such factors, but never completely.
Olive oil is often a marker: it frequently stands for a whole dietary pattern – more vegetables, pulses and fish, fewer ready meals.
No substitute for medicine: none of this work shows that olive oil cures or prevents a disease. It shows differences in statistical risk across large groups.
Other good oils are not worse: against rapeseed, flaxseed or other vegetable oils, the Harvard analysis found no significant advantage.

What may officially be claimed

Health claims are strictly regulated in the EU and Switzerland. For olive oil, essentially two statements are authorised (Regulation (EU) No 432/2012):

Olive oil polyphenols contribute to the protection of blood lipids from oxidative stress – permitted for oils with at least 5 mg of hydroxytyrosol and its derivatives per 20 grams, at a daily intake of 20 grams.
Replacing saturated fats with unsaturated fats helps maintain normal blood cholesterol levels.

Anything beyond that – "olive oil extends life", "protects against dementia" – is neither authorised nor supported by the evidence.

Practical guide: how much, when, which oil

The amount

Amount per day	Equivalent to	Context
7 g	a good half tablespoon	threshold in the Harvard cohorts
20 g	2 tablespoons (Swiss measure: 1 tbsp = 10 g)	reference amount for the EU polyphenol claim
20 g	2 tablespoons of vegetable oil	Swiss dietary recommendation (FSVO) for vegetable oils in total, including at least 1 tbsp of rapeseed oil
approx. 50 g	around 1 litre per week	the amount used in PREDIMED

One tablespoon of olive oil provides around 90 kilocalories. Anyone using two tablespoons a day should cut other fats accordingly. For butter, margarine and similar fats, the FSVO recommends a maximum of 10 grams a day anyway.

Seven rules for everyday use

Replace rather than add: butter on vegetables, cream in a sauce, ready-made dressing on salad – that is where the switch counts most according to the evidence.
Buy extra virgin: only this grade contains meaningful amounts of polyphenols. Refined "olive oil" has almost none.
Check the harvest date: the fresher, the more polyphenols. An oil from the latest harvest beats one that has sat on the shelf for two years.
Dark glass or tin: light degrades polyphenols. Clear bottles under bright shop lighting are a warning sign.
Store it properly: cool, dark, tightly closed, not next to the stove. Details in How to store olive oil.
Cook with it too: thanks to oleic acid and polyphenols, extra virgin olive oil is remarkably heat-stable. Save the best bottle for salads and finishing, where all the aromas survive.
Spread it over the day: a spoon in the salad, a splash over the soup, a thread on bread – that easily adds up to the amounts used in the studies.

How to recognise a polyphenol-rich oil

By bitterness and a peppery catch in the throat. In tasting, both count as marks of quality, not as faults. Early-harvest oils and varieties such as Picual, Cornicabra, Coratina, Moraiolo or Koroneiki deliver particularly high levels; the overview is in Olive varieties in Europe, the background in Polyphenols and antioxidants in olive oil.

And in Switzerland?

Swiss per-capita consumption was around 1.7 kilos a year in 2016 – roughly 4.7 grams a day, and thus below the threshold at which the Harvard cohorts saw a difference. The gap is small: one extra tablespoon a day closes it. Which oils perform well in Swiss shops is covered in our Swiss olive oil test 2026; how much a day makes sense, and what the Swiss authorities say about it, is worked through in How much olive oil per day?; everyday recipes are in Swiss recipes with olive oil.

Frequently asked questions

How much olive oil should you eat daily?

In the Harvard cohorts the difference appeared from a good half tablespoon (7 grams) a day. The EU polyphenol claim refers to 20 grams daily. The Swiss recommendation for vegetable oils in total is 2 tablespoons a day, including at least one tablespoon of rapeseed oil.

Does olive oil extend life?

Not in those terms. Observational studies show a lower mortality risk with regular consumption, especially where olive oil replaces butter, margarine or mayonnaise. That is not proof of causation.

Is olive oil better than rapeseed oil?

In the large US analysis there was no significant difference between olive oil and other vegetable oils. The advantage showed up against animal and processed fats.

Does daily olive oil make you gain weight?

Only if it is eaten on top of everything else. A tablespoon has around 90 kilocalories; as a replacement for butter or a cream sauce, the energy balance hardly changes.

Does it have to be extra virgin?

For the polyphenols, yes. Refined oils contain virtually none – and those are precisely the compounds the only authorised EU claim refers to.

Sources

Note: This article is for general information only and does not replace advice from a doctor or dietitian. If you have health questions, please consult a professional.