Is olive oil good for your heart? What the research shows

Olive oil is the main fat in the traditional Mediterranean diet, and it has built a reputation as one of the healthiest foods in the kitchen. Much of that reputation rests on a single large Spanish trial, plus many studies that followed people’s eating habits over time.

The trial found fewer heart attacks, strokes and heart deaths among people assigned to a Mediterranean diet with extra-virgin olive oil than among people advised to cut fat. Its first report was withdrawn over problems with how participants were assigned, and a reanalysis reached a similar conclusion. Cohort studies point the same way, but they cannot separate olive oil from the diet and lifestyle around it.

What sets olive oil apart from other fats

MedlinePlus describes saturated fat, found in foods such as butter, cheese, red meat and palm and coconut oils, as one of the unhealthy fats, because it raises LDL (bad) cholesterol. It describes monounsaturated and polyunsaturated fats as healthier, noting that these fats tend to be liquid at room temperature. It cites the Dietary Guidelines for Americans, which recommend keeping saturated fat below 10% of daily calories.

Olive oil is rich in oleic acid. As the US Food and Drug Administration (FDA) puts it, oleic acid is a monounsaturated fat that may lower the risk of heart disease when it takes the place of fats higher in saturated fat.

What the PREDIMED olive oil trial found

PREDIMED (Prevention with Mediterranean Diet), reported in the New England Journal of Medicine, enrolled 7,447 people in Spain aged 55 to 80, 57% of them women. All were at high risk of heart disease but did not have it. They were assigned to one of three diets: a Mediterranean diet with free extra-virgin olive oil, a Mediterranean diet with free mixed nuts, or a control diet with advice to reduce dietary fat.

After a median of 4.8 years, 288 people had a major cardiovascular event, meaning a heart attack, stroke or death from heart disease. That happened to 3.8% of the olive oil group, 3.4% of the nuts group and 4.4% of the control group. After adjustment, risk was about 31% lower with the olive oil diet. The authors concluded that major cardiovascular events were lower among those assigned to a Mediterranean diet supplemented with extra-virgin olive oil or nuts than among those given the reduced-fat diet.

The trial has a complicated history. Its first results, published in 2013, were withdrawn after the researchers found protocol deviations: some household members had been enrolled without randomization, and one site had assigned some participants without randomizing them. The 2018 reanalysis used methods that did not assume everyone was randomly assigned, and results were similar after the omission of 1,588 participants whose assignments were in doubt.

What cohort studies show about olive oil

An observational analysis of PREDIMED participants, published in BMC Medicine, looked at how much olive oil people actually used. Those in the top third for extra-virgin olive oil had 39% lower cardiovascular disease risk than those in the bottom third. It found no significant associations for cancer and all-cause mortality, meaning no clear link with cancer or overall death, only with heart outcomes.

A 2014 meta-analysis pooled 32 cohort studies with 841,211 people. Comparing the highest and lowest thirds of intake, monounsaturated fat and olive oil together were linked to 11% lower risk of death from any cause and 17% lower risk of stroke. When the sources were separated, only olive oil seems to be associated with reduced risk; monounsaturated fat from mixed animal and plant sources was not.

What the FDA and health agencies say about olive oil

In 2018 the FDA agreed to allow a qualified health claim for oils with at least 70% oleic acid, including some olive oils. The claim says that supportive but not conclusive evidence suggests about 1.5 tablespoons (20 grams) a day of such oils may reduce the risk of coronary heart disease, when they replace fats and oils higher in saturated fat and do not add to total daily calories.

A qualified claim is a lower bar than a full health claim. It signals that the evidence is suggestive rather than settled. MedlinePlus, for its part, frames the issue as swapping saturated fats for healthier ones rather than adding any single food.

Why the olive oil evidence is hard to interpret

PREDIMED tested a whole Mediterranean diet with supplied olive oil against advice to eat less fat, so it cannot show how much of the benefit came from the oil itself. Its participants were older Spanish adults at high risk, the trial stopped early, and its randomization problems mean the results rest partly on statistical adjustment.

Cohort studies measure olive oil through questionnaires, and people who use a lot of it, especially in Mediterranean countries, may eat differently in other ways too. Oils are also dense in calories, which is why the FDA claim applies only when olive oil replaces other fats rather than adding to them.

What the olive oil research cannot tell us yet

The evidence says little about people at low risk of heart disease, or about olive oil added to diets far from the Mediterranean pattern. It does not settle how much olive oil is best, or whether extra-virgin oil offers more than refined olive oil in a direct comparison.

What the olive oil evidence adds up to

A Mediterranean diet with extra-virgin olive oil lowered heart attacks, strokes and heart deaths compared with a low-fat diet in one large trial, and cohort studies link olive oil with lower risk of heart disease, stroke and death. The benefit appears tied to using olive oil in place of saturated fats, within an overall healthy diet.

Where olive oil fits in any one person’s diet depends on the rest of what they eat and their overall calorie needs.