Extra Virgin Olive Oil for Blood Sugar, Heart and Longevity

Quick answer

Extra virgin olive oil (EVOO) is a core part of the Mediterranean diet. In trials and large cohorts, olive oil is linked to better heart health and, in type 2 diabetes, modestly better blood sugar. Higher-polyphenol oil lowered some oxidative stress markers in one trial. Most of the evidence is about the whole diet, not the oil alone. EVOO is not a treatment for any condition.

Introduction

Extra virgin olive oil is made by pressing olives without chemical refining. It contains monounsaturated fat and plant compounds called polyphenols. This guide covers what the research shows for heart health, blood sugar, mortality and thinking skills, and where the evidence is thin.

What makes EVOO different?

Olive oil is mostly monounsaturated fat. Virgin olive oils also contain more phenolic compounds than refined olive oil (Covas et al., 2006). Polyphenol levels vary a lot between bottles. They depend on the olives, harvest, processing and storage. Most labels do not list them.

Do polyphenols matter?

The EUROLIVE trial tested this directly. 200 healthy men took 25 mL a day of three olive oils for 3 weeks each. The oils had low, medium or high phenolic content but were otherwise similar.

• HDL cholesterol rose slightly with all three oils, a little more with higher phenolic content.
• Markers of oxidative stress, including oxidized LDL, fell as phenolic content rose.

The authors concluded that phenolic content adds benefit beyond the fat itself. The trial was short, used self-reported diet, and measured markers rather than heart attacks or strokes (Covas et al., 2006).

Heart health: the PREDIMED trial

PREDIMED enrolled 7,447 adults in Spain, aged 55 to 80, at high cardiovascular risk. They were assigned to one of three diets:

• A Mediterranean diet with free extra-virgin olive oil
• A Mediterranean diet with free mixed nuts
• A control diet (advice to cut dietary fat)

After a median of 4.8 years, the olive oil group had a lower rate of major cardiovascular events. The hazard ratio was 0.69 (95% CI 0.53 to 0.91) versus control. The original 2013 report was withdrawn after protocol problems with randomization. This 2018 version is the corrected and republished analysis, and the results were similar (Estruch et al., 2018).

This tested a whole Mediterranean diet plus olive oil, not olive oil alone. It does not show that high-polyphenol oil did better than other olive oil.

Blood sugar and type 2 diabetes

Evidence on olive oil and blood sugar is modest.

• In PREDIMED-Reus (418 adults without diabetes), diabetes was diagnosed in 10.1% of the olive oil group and 17.9% of the control group over a median of 4 years. The adjusted hazard ratio was 0.49 (95% CI 0.25 to 0.97). The result held without significant weight change (Salas-Salvadó et al., 2011).
• A 2017 meta-analysis found 16% lower risk of type 2 diabetes in the highest olive oil intake group versus the lowest (RR 0.84, 95% CI 0.77 to 0.92) across four cohort studies. In people who already had type 2 diabetes, olive oil lowered HbA1c by 0.27 percentage points and fasting glucose by 0.44 mmol/L versus control diets. The authors said the findings apply to olive oil as a food, not necessarily to its single components (Schwingshackl et al., 2017).

These effects are small. They come from diets that also changed other foods, so the oil’s share is unclear.

Longevity

In the Nurses’ Health Study and Health Professionals Follow-up Study, 92,383 US adults were followed for up to 28 years. Those who ate the most olive oil (more than about half a tablespoon a day) had a 19% lower risk of death from any cause than those who rarely or never ate it (HR 0.81, 95% CI 0.78 to 0.84). Lower risks were also seen for cardiovascular, cancer, neurodegenerative and respiratory deaths. Replacing margarine, butter, mayonnaise or dairy fat with olive oil was linked to lower risk. Comparing olive oil with other vegetable oils combined showed no significant difference (Guasch-Ferré et al., 2022).

This is observational. People who use more olive oil may differ in other ways, so it does not prove that olive oil extends life.

Brain health

A PREDIMED sub-study followed 447 cognitively healthy older adults for a median of 4.1 years. Those on a Mediterranean diet with olive oil scored better than controls on two of the cognitive tests, with no differences on the others. On the combined global composite, controls declined while the olive oil group stayed near baseline (Valls-Pedret et al., 2015). Follow-up tests were available for only 334 participants. This does not show that olive oil prevents dementia.

Limits of the evidence

• The strongest trials test the Mediterranean diet as a whole, not olive oil alone.
• Cohort studies show association, not cause.
• Polyphenol content is rarely on the label, so you usually cannot know it.
• Olive oil is high in calories. It replaces other fats best when it is a swap, not an addition.

Choosing and using EVOO

• Look for “extra virgin” on the label. Refined olive oils have fewer phenolic compounds.
• Use it in place of butter, margarine or mayonnaise, as the cohort data suggests.
• Use it as part of meals you already eat: on salads, vegetables, grains or fish.

If you take blood sugar or blood pressure medicines, or have a health condition, ask your clinician about changes to your diet.

For related guides, see reversing prediabetes, Mediterranean vs. low-carb eating and foods for blood sugar.

Tracking with Helsa

Helsa lets you log meals by photo or voice, including the oils you cook with. If you also log glucose or weight, you can look back at how your readings change as your habits change. This is a personal record, not proof that one food caused a change.

Key takeaways

• Mediterranean diets with olive oil lowered cardiovascular events and diabetes incidence in PREDIMED.
• In type 2 diabetes, olive oil was linked to small improvements in HbA1c and fasting glucose.
• Higher-polyphenol oil lowered some oxidative stress markers in a short trial.
• Large cohorts link olive oil to lower mortality, but this does not prove cause.
• Swapping olive oil in for butter or margarine is a simple, evidence-backed step.

This article is for information only. It is not medical advice.

References

1. Covas MI et al. The effect of polyphenols in olive oil on heart disease risk factors: a randomized trial. Ann Intern Med. 2006. PubMed
2. Estruch R et al. Primary prevention of cardiovascular disease with a Mediterranean diet supplemented with extra-virgin olive oil or nuts. N Engl J Med. 2018. PubMed
3. Salas-Salvadó J et al. Reduction in the incidence of type 2 diabetes with the Mediterranean diet: results of the PREDIMED-Reus nutrition intervention randomized trial. Diabetes Care. 2011. PubMed
4. Schwingshackl L et al. Olive oil in the prevention and management of type 2 diabetes mellitus: a systematic review and meta-analysis of cohort studies and intervention trials. Nutr Diabetes. 2017. PubMed
5. Guasch-Ferré M et al. Consumption of olive oil and risk of total and cause-specific mortality among U.S. adults. J Am Coll Cardiol. 2022. PubMed
6. Valls-Pedret C et al. Mediterranean diet and age-related cognitive decline: a randomized clinical trial. JAMA Intern Med. 2015. PubMed