Extra virgin olive oil has long been associated with the Mediterranean diet and its potential health benefits. One particularly interesting area of research is whether EVOO may play a role in the relationship between Mediterranean-style eating and breast cancer risk.
Researchers have investigated this question for years, and some studies have produced compelling results.
But as with many areas of nutrition research, the complete picture is more complicated than a single headline.
The PREDIMED Study
One of the most notable studies came from PREDIMED, a large randomized clinical trial conducted in Spain.
Researchers enrolled thousands of adults at high risk for cardiovascular disease and randomly assigned them to different dietary interventions.
For an analysis involving breast cancer, women were assigned to one of three groups:
- A Mediterranean diet supplemented with extra virgin olive oil
- A Mediterranean diet supplemented with mixed nuts
- A control group advised to reduce dietary fat
Participants in the EVOO group were provided with extra virgin olive oil and encouraged to consume it regularly.
Breast cancer incidence was a prespecified secondary outcome of the study.
What Did Researchers Find?
Among the women included in the analysis, researchers observed 35 confirmed cases of invasive breast cancerduring the study period.
Women assigned to the Mediterranean diet supplemented with EVOO experienced a substantially lower rate of breast cancer compared with women in the control group.
The statistical analysis suggested approximately a 68% lower relative risk in the EVOO group.
That's an impressive number—and one of the reasons the study received so much attention.
But it needs context.
Breast cancer was not the primary outcome of PREDIMED, and the number of breast cancer cases was relatively small.
The researchers therefore described the findings as preliminary and called for additional studies with more breast cancer cases and longer follow-up.
What Has Research Found Since Then?
Scientists have continued investigating the relationship between olive oil consumption and breast cancer.
The results have not always been consistent.
Some observational and case-control studies have found an association between higher olive oil consumption and lower breast cancer risk, while other prospective studies have not found a statistically significant relationship.
A more recent study published in 2025 examined olive oil consumption and breast cancer risk and also reviewed the existing scientific literature.
Researchers found some potentially favorable associations, including with certain hormone-receptor-defined breast cancers. However, when they reviewed previous studies, they found that results differed depending on the type of research.
Case-control studies and the PREDIMED randomized trial generally suggested a protective association, while prospective observational studies did not consistently demonstrate one.
In other words, there is promising evidence, but the question isn't settled.
What About the Mediterranean Diet?
Looking beyond olive oil alone, researchers have also examined the Mediterranean dietary pattern as a whole.
A 2025 meta-analysis examining 31 studies found that greater adherence to a Mediterranean diet was associated with approximately a 13% lower risk of breast cancer overall.
The association appeared stronger among postmenopausal women, while researchers did not find a significant reduction among premenopausal women.
That doesn't tell us that olive oil alone is responsible.
The Mediterranean diet includes vegetables, fruits, legumes, whole grains, nuts, fish and other foods in addition to olive oil.
Still, EVOO is one of the defining foods of the traditional Mediterranean dietary pattern.
Why Are Researchers Interested in EVOO?
Extra virgin olive oil has several characteristics that make it particularly interesting to researchers.
First, it is naturally rich in oleic acid, a monounsaturated fatty acid.
EVOO also retains naturally occurring biophenols and other phenolic compounds from the olive fruit because it is mechanically extracted without refining.
Researchers have studied these compounds for their antioxidant and anti-inflammatory activity and continue to investigate how they may interact with cellular pathways involved in disease development.
Laboratory research has also explored how individual compounds found in EVOO may influence processes such as oxidative stress, inflammation, cell proliferation and cell signaling.
However, biological effects observed in a laboratory should not be interpreted as proof that consuming EVOO prevents or treats cancer in people.
Does More EVOO Mean More Protection?
We don't know.
Some studies have observed stronger associations at higher levels of olive oil consumption, but the available evidence does not establish a specific amount of EVOO that someone should consume to prevent breast cancer.
That's why claims such as “two tablespoons of EVOO a day prevents breast cancer” go beyond what current research can support.
Diet is also only one part of breast cancer risk. Age, genetics, alcohol consumption, physical activity, body weight, reproductive history and numerous other factors can influence an individual's risk.
Extra Virgin vs. Refined Olive Oil
Another question researchers continue to investigate is whether the type of olive oil matters.
All olive oil contains substantial amounts of oleic acid.
Extra virgin olive oil, however, also retains naturally occurring biophenols, aromas, flavors and other minor compounds that are substantially reduced during refining.
This gives researchers good reason to study EVOO specifically.
It does not yet give us enough evidence to say that EVOO itself prevents breast cancer.
The Takeaway
Research into extra virgin olive oil and breast cancer is genuinely promising.
The PREDIMED randomized trial found a substantially lower incidence of breast cancer among women assigned to a Mediterranean diet supplemented with EVOO compared with women advised to follow a low-fat diet.
Newer research continues to investigate the association, but results across different types of studies have not been completely consistent.
The evidence therefore doesn't support saying that extra virgin olive oil prevents breast cancer.
What it does support is continued scientific interest in EVOO and the Mediterranean diet—and in the oleic acid, biophenols and other naturally occurring compounds that make extra virgin olive oil such a fascinating subject of nutrition research.
Research Sources
Toledo E, Salas-Salvadó J, Donat-Vargas C, et al. Mediterranean Diet and Invasive Breast Cancer Risk Among Women at High Cardiovascular Risk in the PREDIMED Trial: A Randomized Clinical Trial. JAMA Internal Medicine. 2015.
Olive Oil Consumption and Risk of Breast Cancer: Prospective Results From the Moli-sani Study, and a Systematic Review of Observational Studies and Randomized Clinical Trials. 2025.
Adherence to Mediterranean Diet and Breast Cancer Risk: A Meta-Analysis of Prospective Observational Studies.2025.
This article is for educational purposes only and is not intended to diagnose, treat, cure or prevent any disease or replace individualized medical advice.
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