Olive oil, gut bacteria and heart, metabolic and brain health
What it found
Extra-virgin olive oil may encourage helpful gut bacteria and calm inflammation, and studies in people link it to better heart, blood sugar and memory measures.
Much of the detail comes from animal and lab work.
What they found
Studies in people
Heart events in people
In the PREDIMED trial of 7447 people at high heart risk, a Mediterranean diet plus extra-virgin olive oil or nuts was linked to a 30% lower risk of major heart events over a median of 4.8 years, compared with a low-fat diet.
Blood sugar and fats
In 30 people with impaired fasting glucose, adding 10 g of extra-virgin olive oil to meals was linked to lower blood glucose, triglycerides and other markers. A separate study of 25 people found similar changes after a Mediterranean-type meal with 10 g of the oil.
Gut bacteria in people
In 18 overweight or obese people, a Mediterranean diet with 40 g a day of extra-virgin olive oil for 3 months raised levels of lactic acid bacteria. In 32 people with HIV, 50 g a day for 12 weeks raised Bifidobacteriaceae in those not on antiretroviral treatment.
Memory and thinking
In the PREDIMED-NAVARRA trial of 522 people, a Mediterranean diet with extra-virgin olive oil or nuts was linked to better scores on thinking tests after 6.5 years. A French study of 6947 people found those who used olive oil had lower odds of some cognitive deficits.
Animal and lab studies
Gut bacteria in animals
Rodent studies found extra-virgin olive oil raised bacterial variety and boosted helpful groups like Lactobacillus and Bifidobacterium, while cutting some harmful families such as Desulfovibrionaceae.
Brain changes in mice
In mice bred to develop Alzheimer-like changes, extra-virgin olive oil and its compound oleocanthal reduced amyloid and tau deposits and improved memory and learning.
What the authors conclude
“Consumption of EVOO clearly demonstrates widespread beneficial effects on a variety of aspects of health and disease and also shows great therapeutic potential in positively modifying the gut microbiota as well as the activity and functioning of the mucosal immune system.”
Also in their conclusions
- They say extra-virgin olive oil clearly shows wide benefits for many aspects of health and disease.
- They add that it shows great potential for positively changing gut bacteria and the activity of the gut's immune system.
- They note that how these gut changes influence heart, metabolic, gut and brain health is still a relatively unexplored area with exciting prospects.
How it was done
The authors wanted to look at how extra-virgin olive oil affects gut bacteria and the lining of the gut, and how those changes might feed into heart, metabolic and brain health through the gut-brain link.
They searched PubMed for English-language studies from 2010 to April 2020 on extra-virgin olive oil, its polyphenols, gut bacteria, the immune system, heart health, metabolic health and thinking skills. They pulled together findings from people and from rodents.
What it can’t tell you
- Many of the detailed findings come from mice and lab tests, so they cannot show what happens in people.
- Some human findings come from studies that follow people over time, which can show a link but not prove cause and effect.
- The best amount of extra-virgin olive oil for gut bacteria is still not known.
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 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error