Randomised controlled trialindependent cross-checkabstract only checked★ key study I-FAT-04 in-depth review
Spanish trial: Mediterranean diet with olive oil prevented heart events
Primary Prevention of Cardiovascular Disease with a Mediterranean Diet Supplemented with Extra-Virgin Olive Oil or Nuts.
Overview
Estruch R et al.. N Engl J Med 2018 · PMID 29897866 · DOI 10.1056/NEJMoa1800389
HR 0.69; events 3.8% vs 4.4%.
Does the study support the specific claim? Yes · Methodological quality: moderate
Plain-language summary
Study explained simply
- What did the researchers want to find out?
Test Mediterranean diet.
- How was the study done?
RCT, 4.8 years.
- How many people, animals or samples were studied?
7,447 high-risk adults.
- What was actually found?
Fewer major CV events.
- How large was the observed effect?
HR 0.69 (0.53-0.91).
- What do the results mean in everyday life?
Olive oil as part of a Mediterranean diet benefits the heart.
- What are the study's limitations?
Randomisation problems corrected.
- What does it say about Elawady's specific claim?
Supports olive oil.
- Do the results apply to Germany and Europe?
High.
- What can explicitly not be concluded from this study?
Effect of olive oil alone.
Scientific in-depth review
1. Full reference
- Authors
- Estruch R et al.
- Journal
- N Engl J Med
- Year
- 2018
- Identifier
- PMID 29897866 DOI 10.1056/NEJMoa1800389
- Verification
- verified – PubMed efetch 2026-10-25
- Retracted
- no
- Corrections
RepublishedFrom: N Engl J Med. 2013 Apr 4;368(14):1279-90. doi: 10.1056/NEJMoa1200303.; RepublishedFrom: N Engl J Med. 2018 Jun 21;378(25):2441-2442. doi: 10.1056/NEJMc1806491.
- Extent checked
- abstract only
- Conflicts of interest and funding
Funded by Instituto de Salud Carlos III, Spanish Ministry of Health, and others (abstract); 2013 report withdrawn due to randomisation irregularities.
2. Research question
Mediterranean diet with EVOO or nuts vs reduced-fat control for primary CVD prevention.
3. Study design and population
- Study design
- Randomised controlled trial – Multicentre randomised trial (PREDIMED), corrected and re-published 2018.
- Population
7,447 adults aged 55-80 at high CV risk
- Country
Spain
- Period
Median follow-up 4.8 years
- Sample size
7,447
- Inclusion and exclusion criteria
High CV risk, no CVD.
4. Methods and endpoints
- Exposure / intervention
Mediterranean diet + EVOO; Mediterranean diet + nuts
- Comparator
Advice to reduce dietary fat
- Endpoints
MI, stroke or CV death.
- Statistical methods
ITT, adjusted, propensity scores.
5. Actual results
- Results
Events: EVOO 96 (3.8%), nuts 83 (3.4%), control 109 (4.4%); HR 0.69 (0.53-0.91) EVOO; 0.72 (0.54-0.95) nuts; similar after excluding 1,588 participants with protocol deviations.
- Absolute risks
3.8% vs 4.4% (EVOO vs control) over ~4.8 years.
- Authors' conclusion
Incidence of major cardiovascular events lower with Mediterranean diet + EVOO or nuts vs reduced-fat diet.
6. Strengths
- Large RCT, hard endpoints
7. Weaknesses
- Randomisation irregularities at some sites (corrected analysis)
- Whole-diet intervention, not olive oil alone
- Control diet adherence limited
8. Risk of bias
- Orienting tool
- RoB 2
- Type of assessment
- simplified assessment (abstract only)
- Full formal assessment
- no
- Overall risk of bias
- some concerns
- Rationale
Randomisation deviations; re-analysis addresses partly.
9. Assessment of the statistical interpretation
Moderate relative reduction; small absolute difference.
10. Relevance to the specific claim
Supports C-FAT-03; contradicts C-FAT-04.
11. Independent contrary findings
n/a
12. Transferability to Germany and Europe
High (Mediterranean Europe).
13. Overall methodological judgement
Best trial evidence for olive oil within a diet.
| Multidimensional assessment | |
|---|---|
| Authenticity of the source | verified |
| Methodological quality | moderate |
| Risk of bias | some concerns |
| Precision of results | moderate |
| Directness | direct |
| Reproducibility | partly replicated |
| Consistency with the overall evidence | consistent |
| Regional transferability | moderate |
| Adequacy of the interpretation (by the archive) | not applicable |
14. Open questions
Olive oil alone.
15. Linked fact checks
- Olive oil is an allowed fat in the system. – Studies supporting the claim
- Olive oil (and flaxseed oil) should be avoided because it is adulterated ('it is all fake') and has a problem with its acidity; instead a little corn oil and sunflower oil should be used for frying. – Studies contradicting or limiting the claim