Study analysis · Nutrients · 2022
Could two tablespoons of extra-virgin olive oil a day help protect your brain? New study suggests it may tighten the blood-brain barrier and improve memory in people with early cognitive decline.
A small six-month study found that daily extra-virgin olive oil improved brain barrier integrity and connectivity in people with mild memory problems, while both extra-virgin and refined olive oil improved certain memory scores and blood markers linked to Alzheimer's.
Overview
What the study found
The study in plain English — the bottom line, every takeaway we extracted, and what to do with them.
In simple terms
This study is like a test where people were randomly put into two groups: one got a special olive oil with extra healthy ingredients, the other got a similar oil without those ingredients. They checked their brain scans and memory tests before and after. Because it's a random test, we can be fairly sure that any differences between the groups are because of the oil. But the study was small, so we can't be completely sure. We learned that the special oil might help with the brain's blood vessel barrier, but we can't say for sure it makes memory better.
What’s the bottom line?
This study looked at whether daily olive oil for 6 months could help people with mild memory problems. They tried two types: one extra virgin with lots of natural plant chemicals, and one refined without them. They measured brain health using MRI scans and memory tests. Results: Only the extra virgin olive oil improved the barrier around the brain and made brain areas talk better to each other. Both oils improved memory test scores and reduced some proteins linked to Alzheimer's disease. But the study was small, so more research is needed.
How strong is this study?
This study was done carefully. The people were randomly divided into two groups, and neither the participants nor the doctors knew who got which oil until the end, which makes the results more trustworthy. However, only 25 people took part, and the study lasted only 6 months. That means we need bigger and longer studies to be more confident that the results are real and not just by chance.
40 / 100
- COI disclosure+40/40
- Data availabilitydata not shared
- Code availabilitycode not shared
78 / 100
- Randomization+20/20
- Blinding+15/15
- Control group+15/15
- Sample size (n=25)+2.4/20
- Follow-up+10/10
100 / 100
100 / 100
- P-values+15/15
- Effect size+20/20
- Confidence intervals+15/15
- Pre-registration+15/15
Each component is scored out of 100 and then capped by the study design — a case series cannot reach the ceiling a randomised trial can, however well it is reported.
Where it sits
RCT reviewsReviews of RCTs (Meta-analyses)
Max 100Randomized TrialsRandomized Trials
Max 90Reviews of Cohort StudiesReviews of Cohort Studies
Max 85Cohort StudiesCohort Studies
Max 72Reviews of Case-Control StudiesReviews of Case-Control Studies
Max 63Case-Control StudiesCase-Control Studies
Max 58Cross-Sectional & Case SeriesCross-Sectional & Case Series
Max 50Expert OpinionExpert Opinion
Max 580 / 100
Probability of being correct
Participants are randomly assigned to treatment or control groups, minimizing bias. The gold standard for testing whether an intervention causes an effect.
This design can establish causation. Although the RCT design can establish causation, this pilot study has limitations: small sample size, short duration, no true placebo control (only active comparator), and some outcomes showed within-group but not between-group differences. Thus, causal claims should be limited to outcomes with significant group × time interactions, such as BBB permeability and functional connectivity.
Major COI
Major conflicts that significantly reduce study credibility
The study received in-kind support from OLIVE FABRICA, which supplied the extra-virgin olive oil used in the trial. No explicit funding or conflict of interest declarations were provided. This creates a potential conflict of interest due to the product supplier's interest in the outcome.
Funders
Conflict Details
OLIVE FABRICA: Provided the extra-virgin olive oil used in the study free of charge.
Independent Analysis Safeguards
- Participants, investigators, and research assistants were blinded to treatment group.
- Randomization was performed by blind withdrawal of labels.
- All assays and MRI analyses were performed by investigators blinded to olive oil type.
No explicit funding statement or COI section was found in the text. The supply of EVOO by a commercial entity introduces a potential bias. The study is a small proof-of-concept trial.
Key takeaways
- 01
25 people with mild cognitive impairment took either 30 mL of extra-virgin olive oil or refined olive oil daily for 6 months.
- 02
The extra-virgin group had better brain scans showing less leaking in the brain's protective barrier and better communication between brain regions.
- 03
Both groups scored better on memory tests and had lower levels of Alzheimer's-related proteins in their blood.
- 04
No one gained weight.
- 05
The improvements seen might be modest but significant for people with mild cognitive impairment, suggesting that simple diet changes could help brain health.
- 06
But because the study was small and short, we can't be sure these benefits will last or apply to everyone.
Surprising findings
- Refined olive oil (ROO) improved clinical dementia rating scores and reduced Alzheimer's biomarkers, despite having no effect on BBB permeability or connectivity.It was expected that only polyphenol-rich EVOO would have brain benefits, but ROO also showed cognitive improvements, suggesting the monounsaturated fat component (oleic acid) may have independent benefits.
- EVOO increased serum neurofilament light (NFL) levels, a biomarker often associated with neuronal damage, yet this was not significantly different from ROO.NFL levels usually increase with neurodegeneration, but EVOO showed a slight increase, which is counterintuitive given the other positive effects. This could be due to individual variability or unrelated factors.
- ROO increased brain activation during a working memory task, while EVOO decreased activation in some motor areas, but these changes were not significantly different between groups.It was thought that EVOO would have a more robust effect on brain function, but ROO showed increased activation in cortical regions, suggesting both oils may influence brain activity through different mechanisms.
Practical takeaways
Consider incorporating 30 mL (about 2 tablespoons) of extra-virgin olive oil into your daily diet, preferably raw, as a potential strategy to support brain health, especially if you have mild cognitive impairment or are at risk for Alzheimer's.
This is a small pilot study. Always consult a healthcare provider before making significant dietary changes, and remember that olive oil is calorie-dense, so moderation is key.
medium confidenceIf extra-virgin olive oil isn't accessible, refined olive oil may still offer some benefits for cognition and biomarkers, but it lacks the specific BBB and connectivity improvements seen with EVOO.
The study didn't include a true control group, so we can't be sure the benefits aren't due to placebo or other lifestyle factors.
low confidenceWhy this study matters
Extra-virgin olive oil improved blood-brain barrier function
In a randomized, double-blind trial, 25 adults with mild cognitive impairment (MCI) consumed 30 mL (about 2 tablespoons) of extra-virgin olive oil (EVOO) or refined olive oil (ROO) daily for 6 months. MRI scans showed that EVOO significantly reduced blood-brain barrier (BBB) permeability in the hippocampus and parahippocampal gyrus, indicating tighter barrier integrity, while ROO had no effect on these primary outcomes.
The blood-brain barrier protects the brain from toxins and regulates nutrient flow. Leakiness is linked to Alzheimer's progression, so improving it could be a simple preventive step.
EVOO enhanced brain connectivity, but ROO did not
Resting-state fMRI revealed that EVOO strengthened functional connectivity between the parahippocampal gyrus and regions like the precuneus and prefrontal cortex, while ROO showed no significant changes. This suggests polyphenols in EVOO, not just monounsaturated fats, drive brain network improvements.
Better connectivity means improved communication between brain regions, which is crucial for memory and cognition.
Both olive oils improved dementia rating and reduced Alzheimer's biomarkers
After 6 months, both EVOO and ROO significantly improved Clinical Dementia Rating (CDR) scores (EVOO: -0.154, ROO: -0.292) and reduced plasma Aβ42/Aβ40 and phosphorylated tau/total tau ratios. For example, Aβ42/Aβ40 decreased by 0.0036 in EVOO and 0.0034 in ROO. This suggests both types have benefits, possibly from the monounsaturated fat content.
Even refined olive oil, which lacks polyphenols, offered benefits, pointing to oleic acid or other components. This gives consumers more options.
EVOO improved memory scores, but not significantly better than ROO
EVOO significantly improved logical memory overall and delayed recall on the WMS-IV test, while ROO improved immediate visual reproduction. However, between-group differences were not statistically significant, meaning we can't say EVOO is better than ROO for cognition.
This nuance prevents overstating EVOO's superiority; both oils may help cognition, but larger studies are needed.
No weight gain from daily olive oil
Participants consumed 30 mL of olive oil daily for 6 months without significant weight change. Average body weight stayed almost identical in both groups (EVOO: 85.1 to 85.7 kg; ROO: 74.3 to 74.4 kg). This counters fears that adding olive oil to the diet causes weight gain.
Many avoid olive oil due to calorie concerns, but this study suggests it can be incorporated without weight gain, possibly due to satiety or metabolic effects.
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1 video from Physionic cite this study, drawing 4 claims from it.
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Evidence - Conflicting evidence
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Evidence - Very strong evidence
Randomized or controlled trials support this claim, alongside consistent supporting evidence.
Evidence - Very strong evidence
Randomized or controlled trials support this claim, alongside consistent supporting evidence.
Evidence