Extra-virgin olive oil, gut bacteria, heart and brain health
What it found
In people and rodents, extra-virgin olive oil was linked to lower heart disease risk, better memory scores, and more beneficial gut bacteria.
The authors say these benefits may be connected through the gut-brain axis.
What they found
Studies in people
Heart disease in people
In a large trial of 7447 people at high heart risk, eating a Mediterranean diet with extra-virgin olive oil lowered major heart events by 30% compared to a low-fat diet over about 4.8 years. Participants were advised to eat at least 4 tablespoons a day.
Memory and thinking in people
In a trial of 522 people, a Mediterranean diet with extra-virgin olive oil improved memory test scores after 6.5 years compared to a low-fat diet. A separate study following 6947 French adults found that regular olive oil users had fewer problems with visual memory than those who never used it.
Gut bacteria in people
In 18 overweight people, adding 40 g of extra-virgin olive oil daily for 3 months raised levels of lactic acid bacteria. In another small trial, olive oil rich in plant compounds increased Bifidobacteria more than oil with fewer plant compounds.
Animal and lab studies
Brain changes in mice
In mouse models of Alzheimer disease, extra-virgin olive oil or its compound oleocanthal reduced harmful brain proteins called amyloid-beta and tau. Mice given the oil also showed improvements in short-term memory tests.
Gut bacteria in rodents
Rodent studies found that extra-virgin olive oil increased the variety of gut bacteria and boosted helpful types like Lactobacillus and Bifidobacterium. It also suppressed certain bacteria linked to obesity and inflammation.
Other findings
What is in the oil
Extra-virgin olive oil is made by mechanically pressing olives without heat or solvents and must have no more than 0.8% free acidity. Fats make up 98% to 99% of its weight, while plant compounds range from 50 to 940 mg/kg depending on the olive type and growing conditions.
What the authors conclude
- They conclude that extra-virgin olive oil shows clear benefits for heart, metabolic, and brain health while also positively changing gut bacteria and intestinal immunity.
- They suggest that changes in gut bacteria and their products may help explain how the oil supports these different areas of health.
- They note that exactly how these gut changes lead to better heart and brain outcomes still needs much more research.
How it was done
Extra-virgin olive oil is a key part of the Mediterranean diet and contains fats and plant compounds thought to support health. Scientists wanted to understand how it affects gut bacteria and whether those changes might explain its links to heart, metabolic, and brain health.
The authors searched for English-language studies published between 2010 and April 2020 on extra-virgin olive oil, gut bacteria, immunity, and heart or brain health. They gathered findings from human trials, population studies, and rodent experiments to see how the oil influences the gut and body.
What it can’t tell you
- This work gathers many different studies, so it cannot prove that extra-virgin olive oil alone caused every benefit seen in people.
- Many findings on brain proteins and gut bacteria come from rodents, which may not match what happens in the human body.
- Scientists do not yet know the exact amount of extra-virgin olive oil needed to change gut bacteria in people.
Who paid
- Authors work at
- University of the Ryukyus, Okinawa; National Institute of Technology, Okinawa; Fukushima Medical University, Japan
The paper
- Title
- Extra-virgin olive oil and the gut-brain axis: influence on gut microbiota, mucosal immunity, and cardiometabolic and cognitive health
- Type
- ReviewThe authors read earlier studies and describe what they found. It isn’t a new study.
- Evidence
- Studies in people · animals · lab
- Summarised from
- Full text
- Cite
- Millman JF, Okamoto S, Teruya T, et al (2021). Extra-virgin olive oil and the gut-brain axis: influence on gut microbiota, mucosal immunity, and cardiometabolic and cognitive health. Nutrition reviews. doi:10.1093/nutrit/nuaa148Free full textPubMed 33576418DOI
Summary written 30 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error