In the largest randomized trial to test it, a Mediterranean diet cut the rate of major cardiovascular events — heart attack, stroke, or cardiovascular death — by about 28% to 31% over roughly five years, compared with a low-fat control diet, in adults already at high cardiovascular risk. That trial, however, comes with an unusual asterisk: its original 2013 results were retracted over study-conduct problems and had to be re-run through a different analysis before the finding held up.
| Diet group (vs. control) | Cardiovascular event rate | Risk reduction |
|---|---|---|
| Mediterranean diet + extra-virgin olive oil | 3.8% | 31% lower |
| Mediterranean diet + mixed nuts | 3.4% | 28% lower |
| Control diet (advice to reduce dietary fat) | 4.4% | — |
What the PREDIMED trial actually tested
The trial, known as PREDIMED, enrolled 7,447 adults in Spain, aged 55 to 80, with no cardiovascular disease at the start but at high risk for it (diabetes or multiple risk factors like smoking, high blood pressure, or high cholesterol). Researchers assigned each person to one of three diets: a Mediterranean diet supplemented with free extra-virgin olive oil, a Mediterranean diet supplemented with free mixed nuts, or a control diet built around general advice to cut dietary fat. Everyone received quarterly nutrition counseling. After a median of 4.8 years, 288 people had a major cardiovascular event. The rate was lowest in the two Mediterranean-diet groups: 3.8% with olive oil and 3.4% with nuts, versus 4.4% on the control diet.
Why the 2013 results were retracted
In 2013, the same trial reported similar numbers in the same journal. Years later, the investigators discovered protocol deviations: at one site, some household members had been enrolled without being properly randomized; at another, some participants had been assigned to a diet group without randomization; at a third, randomization tables appeared to have been used inconsistently. Rather than let the flawed version stand, the researchers withdrew the 2013 paper and published a new analysis in 2018 that did not rely solely on the assumption that every participant had been randomized correctly. The corrected numbers — the ones in the table above — came out close to the original estimates, and the result held even after excluding the roughly 1,600 participants whose assignment was known or suspected to have departed from the protocol. That a large trial survived a public retraction and a redo with the problem cases handled differently is, if anything, a stronger argument that the finding is real than the original report alone would have been.
Who was in the trial, and does that matter for you?
PREDIMED enrolled adults who were already at high cardiovascular risk — most had diabetes or several risk factors like smoking, high blood pressure, or high cholesterol — rather than a general, low-risk population. That matters for how far the result travels: a 28% to 31% relative reduction in cardiovascular events is a meaningful number for someone who already has an elevated baseline risk of those events, but the trial doesn't tell you how much of an absolute difference the same diet would make for someone younger or without those risk factors, because that group wasn't studied here. The broader population evidence below, drawn from cohorts that included people across a wider range of baseline risk, is what fills in that gap — with the weaker footing that comes from being observational rather than randomized.
What the research says
Estruch and colleagues' corrected 2018 analysis of the PREDIMED trial found that, among 7,447 adults at high cardiovascular risk followed for a median of 4.8 years, a Mediterranean diet supplemented with extra-virgin olive oil or mixed nuts reduced the rate of major cardiovascular events by 31% and 28%, respectively, compared with a reduced-fat control diet — a randomized result, which is the strongest kind of evidence a single trial can offer, though it was conducted in Spanish adults already at elevated cardiovascular risk and the dietary difference between groups (free olive oil or nuts, plus more counseling) may not be easy to replicate without those supports.¹
Sofi and colleagues' earlier meta-analysis pooled 12 prospective cohort studies covering more than 1.5 million people followed for 3 to 18 years and found that each 2-point increase in how closely someone followed a Mediterranean-style diet was associated with 9% lower overall mortality, 9% lower cardiovascular mortality, 6% lower cancer incidence or mortality, and 13% lower incidence of Parkinson's and Alzheimer's disease.² These are observational findings — people who ate this way were compared with people who didn't, rather than being randomly assigned to do so — so they show a consistent association across many populations rather than proof that the diet itself caused the difference, and no single standardized scoring method was used across all 12 cohorts.
What you can do this week
- Build meals around the three staples the trial actually tested: olive oil, nuts, and produce. Extra-virgin olive oil as your main fat, a handful of mixed nuts most days, and vegetables, fruit, and legumes at most meals are the specific components PREDIMED supplied — not a long list of rules.
- Swap, don't just add. The trial's benefit came from replacing other fats and foods, not stacking olive oil and nuts on top of an unchanged diet; cutting back on processed and fried foods is part of the same pattern.
- If you're also trying to lose weight, a Mediterranean-style eating pattern and a prescription treatment aren't an either-or. Pallas prescribes compounded semaglutide and tirzepatide when a US-licensed clinician decides it's appropriate.
None of this requires a strict meal plan. The trial's own design was closer to a shift in everyday staples than a diet with rigid daily rules.
