The Study
Total and different types of olive oil consumption, gut microbiota, and cognitive function changes in older adults
This study watched a group of older people for two years. They asked them what they ate, looked at their gut germs, and tested their memory and thinking. They found that people who said they ate more of a special olive oil called virgin olive oil did better on thinking tests, while those who ate more of the regular kind did worse. But this type of study can't prove that the olive oil caused the change – it could be something else about the people.
Analysis score
Maximum 72 for a cohort study.
Where the score came from
This study followed older adults for 2 years and looked at how much of different types of olive oil they ate, the bacteria in their gut, and how their memory and thinking changed. They found that eating more virgin olive oil (like extra virgin) was linked to better brain function, while eating more common olive oil (more refined) was linked to worse brain function. The effect may be through changes in gut bacteria.
Where does this study sit?
Reviews of RCTs (Meta-analyses)
Max 100Randomized Trials
Max 90Reviews of Cohort Studies
Max 85Cohort Studies
Max 72Reviews of Case-Control Studies
Max 63Case-Control Studies
Max 58Cross-Sectional & Case Series
Max 50Expert Opinion
Max 552 / 100
Quality score
Groups of people are followed over time to see who develops an outcome. Strong for identifying risk factors and associations, but cannot prove causation as firmly as RCTs.
Key takeaways
Summary
Based on the study abstract and findings.
- 1The effects are small in terms of test scores (less than 0.1 standard deviation), so they may not be noticeable for an individual, but at a population level they could matter for healthy aging.
- 2The study suggests that choosing virgin olive oil over refined might be a simple dietary change to support brain health.
- 3For every extra 10 grams (about 2 teaspoons) of virgin olive oil per day, people scored about 0.04 points higher on a standardized brain function test.
- 4For common olive oil, every extra 10 grams per day was linked to about 0.03 points lower.
- 5Virgin olive oil also increased gut bacteria diversity, while common olive oil decreased it.
- 6A specific gut bacteria, Adlercreutzia, seemed to help explain the brain benefit from virgin olive oil.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
Microbiome
Year
2026
Authors
Jiaqi Ni, S.K. Nishi, N. Babio, Clara Belzer, J. Vioque, D. Corella, J. Hernando-Redondo, J. Vidal, I. Moreno-Indias, L. Compañ-Gabucio, Ó. Coltell, M. Fíto, E. Toledo, Dong D. Wang, F. Tinahones, J. Salas-Salvadó
Related Content
Claims (10)
Olive oil improves dementia test scores, and this improvement is not caused by the oil's phenolic compounds but by other parts of the oil.
Older adults with metabolic syndrome who eat more virgin olive oil tend to have a wider variety of helpful bacteria in their gut, and the polyphenols in the oil may act as food for these bacteria.
In older adults with metabolic syndrome, eating more regular olive oil is linked to having a smaller variety of gut bacteria. This pattern is seen when measuring gut bacteria in four different ways.
For older people who are overweight and have metabolic problems, eating more common olive oil (the cheaper kind with fewer antioxidants) is linked to a faster decline in memory and thinking over two years. Each extra 10 grams (about two teaspoons) per day is tied to a measurable drop in overall brain function, especially affecting thinking speed, planning, and language skills.
Older adults who are overweight and have health problems like high blood pressure and high blood sugar tend to score better on thinking and memory tests if they eat a bit more olive oil every day for two years.
In older adults with health problems like high blood pressure and blood sugar, the bacteria in their gut play a role in how olive oil affects their thinking and memory. One specific type of gut bacteria, called Adlercreutzia, is responsible for about 20% of that effect.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.