Was the PREDIMED trial retracted?

Yes, in 2018, and it was republished the same day. The reason was not following the study plan, not fraud. Some family members were signed up without being assigned by chance and were put in their relative's group, and assignment by chance broke down at two of eleven sites. Both halves of what came next matter. The event counts were the same, and the risk scores moved by 0.01 or not at all. But the claim that the diet caused the drop got weaker, because the new analysis leans on statistical adjustment rather than on assignment by chance alone.

Is the Mediterranean diet good for weight loss?

Only if you cut calories, and the studies make this unusually clear. PREDIMED gave no advice to cut calories and weight barely changed over five years, yet heart attacks, strokes and heart deaths still went down. DIRECT did cut calories and produced 4.4 kg of weight loss over two years. This diet's strength is heart events, not weight.

Does it actually prevent heart attacks?

It is the only diet with trial evidence on real heart attacks and strokes, and that evidence is real but comes with catches. Two studies in Spain found roughly a 28 to 31 percent lower risk. Both gave free olive oil to the diet groups, and both were partly funded by the olive oil industry. The landmark study had a problem with how people were assigned to groups. And in the study of people who already had heart disease, the benefit was only in men.

Which part of it is doing the work?

Nobody knows, because no study has tested one part on its own. It was tested as a whole diet, and in the two biggest studies the thing handed out free was olive oil or nuts. That is a reason to adopt the whole way of eating rather than to buy one ingredient.

Does it work outside the Mediterranean?

Not tested for real heart outcomes. PREDIMED and CORDIOPREV both ran in Spain, where the usual diet was already closer to this one than a typical North American or Northern European diet. That cuts an interesting way. The gap being closed there was smaller, so a bigger change elsewhere might do more, or people elsewhere might respond differently. Neither has been measured.

Whole-food4 studies in people cited

Mediterranean

Written by Aaron CuhaReviewed Sep 2026

Also called: Med diet, MedDiet, PREDIMED pattern

The only diet with trial evidence on real heart attacks and strokes. Its landmark study was pulled and republished. The size of the effect held up. How sure we can be that the diet caused it did not.

What it actually is

Extra virgin olive oil as the main fat. Lots of vegetables, beans, nuts and fish. Some wine with meals. Little red or processed meat, and little added sugar. In the studies it is not a weight loss diet and was never sold as one. PREDIMED gave no advice to cut calories at all, and weight barely changed over five years.

How its fans say it works

It is a mix, not one lever. The fat in olive oil, in place of saturated fat, improves cholesterol. Plant compounds in olive oil and wine are thought to help blood vessels and limit wear and tear from oxidation. Nuts add healthy fat and fibre, and oily fish adds omega-3. Because it is a whole way of eating, no study has pinned down which part does the work, and the two biggest studies both handed out free olive oil.

What happened when calories were controlled

Best kind of study available: told what to eat, reported it themselves

People were told what to eat and then said what they ate. People usually say they ate less than they did, so what each group really ate is unknown.

Calories were rarely controlled, and that decides what a study means. PREDIMED did not cut calories and got heart benefits without weight loss. DIRECT did cut calories and got weight loss. Mixing up those two is the most common mistake made with this diet.

A 2020 review by Ge pooled 121 studies with 21,942 people. Weight loss faded by twelve months on every type of diet and every named diet. The gains in heart risk factors mostly vanished by twelve months for every diet except the Mediterranean one. That is one result from one review, and we report it at that size.
PREDIMED gave the diet groups free extra virgin olive oil or free mixed nuts. The comparison group got advice to eat less fat, plus small gifts that were not food. That imbalance matters: the diet groups got food, and the comparison group got advice.
DIRECT (Shai, 2008) is the one that cut calories: 322 adults, two years, three diets. Average weight loss was 2.9 kg on low fat, 4.4 kg on Mediterranean and 4.7 kg on low carb. People stuck with it better than in any other study here, 84.6 percent at two years. Among the 36 people with diabetes, blood sugar and insulin moved in a better direction on Mediterranean than on low fat. That was a clear difference, but in only 36 people.

What happened when people just ate it

This is the one diet where studies of people eating freely counted real heart attacks and strokes rather than lab numbers, and that is why it stands apart. PREDIMED assigned 7,447 people at high heart risk and followed them for a typical 4.8 years. It counted heart attacks, strokes and deaths from heart disease. CORDIOPREV assigned 1,002 people who already had heart disease and followed them for seven years. There were 87 of those events on Mediterranean against 111 on low fat, a risk score of 0.719 to 0.753 after adjustment, where under one means fewer events. The Lyon Diet Heart Study looked at people after a first heart attack. It reported 14 heart deaths plus non-fatal heart attacks, against 44 on a cautious Western diet. That last effect, a risk score as low as 0.28, has not been matched by any modern study. It also came before today's statins and artery-opening procedures. So treat it as historically important, not as the effect to expect.

Protein, and whether it muddies the result

Protein is moderate and comes mostly from fish, beans and dairy. The diet was never built around it. None of the heart studies matched or reported protein, and none measured muscle. If you pair this diet with a weight loss drug or serious training, it gives you no protein guidance at all, and you will need to add that yourself.

The measured intakes behind the protein figures are on the protein page.

What reliably moves

Measure	Direction	From
Heart attacks, strokes and heart deaths	Down, and this is the only diet with trial data on them	In the republished PREDIMED, risk scores were 0.69 for olive oil and 0.72 for nuts. CORDIOPREV, in people who already had heart disease, found 0.719 to 0.753. Both studies were partly funded by the olive oil industry, and both gave free olive oil to the diet groups.
Body weight	Barely, or not at all, depending on the study	PREDIMED gave no advice to cut calories, and weight barely changed over five years. DIRECT, which did cut calories, produced 4.4 kg of loss over two years. This diet is not a weight loss plan unless calories are cut.
Blood pressure (top number)	Down, and better than vegan on this one measure	In the only head-to-head against a low fat vegan diet, Mediterranean won on the top blood pressure number by 5.9 mmHg, while losing on weight and LDL. That study was run by a group that promotes plant-based eating, and it published the result against its own diet.
Heart risk factors at twelve months	Kept, when other diets lost them	In a review that pooled 121 studies, gains in heart risk factors mostly vanished by twelve months for every diet except this one. One result, one review.

Long term, and serious health events

The best long-term data of any diet here, and it comes with a retraction we have to report. PREDIMED's 2013 paper was pulled in 2018. The reason was not following the study plan, not fraud. Family members in the same household were signed up without being assigned by chance, and were put in the same group as their relative. At one of eleven sites, some people were assigned without chance. At another, the lists used to assign people seem to have been used unevenly. So part of the study was not properly assigned by chance, and that breaks the thing that lets you say the diet caused the result. The republished paper is the part most people get wrong, in both directions. The event counts are the same: 96, 83 and 109 in the three groups, 288 in total. The risk scores moved by 0.01 or not at all: 0.70 to 0.69 for olive oil, and 0.72 to 0.72 for nuts. They held up even after leaving out 1,588 people whose group assignments were known or suspected to be off-plan. So the size of the effect survived. What did not survive was how firmly we can say the diet caused it. The 2018 analysis uses statistical adjustments for how people differed at the start, rather than relying on assignment by chance alone. That makes part of the evidence more like a study that just watches people. The paper's summary wording changed to match: from saying the diet reduced heart events to saying events were lower among those assigned to it. Both halves belong in any honest report of this study, and most reports carry only one.

Sources

Review of studies2018
Retraction and republication: primary prevention of cardiovascular disease with a Mediterranean diet
New England Journal of Medicine
This is the notice that pulled the 2013 PREDIMED paper. Some people from the same household were signed up without being assigned to a group by chance. At one site some people were placed in groups without chance assignment, and another site seems to have used its assignment tables unevenly.
The retraction notice for the 2013 PREDIMED paper. Protocol deviations: household members enrolled without randomisation, some participants at one site assigned without randomisation, and apparent inconsistent use of randomisation tables at another.
Study in people2018
Primary prevention of cardiovascular disease with a Mediterranean diet supplemented with extra-virgin olive oil or nuts
New England Journal of Medicine
This is the redone analysis of 7,447 adults at high risk of heart disease, followed for about 4.8 years, with 288 major heart or stroke events. The groups given extra olive oil or extra nuts had fewer of these events than the comparison group. That held even after leaving out 1,588 people whose group assignment may have gone wrong. The authors used statistical adjustment rather than relying only on chance assignment.
The republished analysis. 7,447 high-risk adults, median 4.8 years, 288 primary events. Olive oil HR 0.69 (0.53 to 0.91), nuts HR 0.72 (0.54 to 0.95), holding after omitting 1,588 participants with suspected protocol departures. Adjusted for baseline characteristics and propensity scores rather than relying on randomisation alone.
Study in people2022
Long-term secondary prevention of cardiovascular disease with a Mediterranean diet and a low-fat diet (CORDIOPREV): a randomised controlled trial
The Lancet
1,002 people who already had heart disease ate a Mediterranean diet or a low fat diet for seven years. There were 87 heart events on Mediterranean against 111 on low fat. The benefit showed up in men; in the 175 women there was no difference. Olive oil industry groups paid for part of the study.
1,002 patients with established coronary heart disease, seven years. 87 events on Mediterranean against 111 on low fat, adjusted HR 0.719 to 0.753. The effect was concentrated in men (HR 0.669); no difference found in the 175 women. Funded in part by olive oil industry bodies.
Study in people1999
Mediterranean diet, traditional risk factors, and the rate of cardiovascular complications after myocardial infarction: final report of the Lyon Diet Heart Study
Circulation
People who had survived a first heart attack were followed for about 46 months. On the Mediterranean-style diet there were 14 heart deaths and repeat heart attacks, against 44 in the comparison group, a clear gap. The event counts were very small, and the study came before modern statins and artery-opening procedures.
Secondary prevention after a first myocardial infarction, mean 46 months. Cardiac death plus non-fatal infarction 14 against 44 events, p = 0.0001, with adjusted risk ratios 0.28 to 0.53. Very small event counts and predates modern statin and revascularisation care.
Study in people2008
Weight loss with a low-carbohydrate, Mediterranean, or low-fat diet
New England Journal of Medicine
322 adults followed one of three diets for two years. Here the Mediterranean diet had a calorie limit, unlike in PREDIMED. Weight loss was 2.9 kg on low fat, 4.4 kg on Mediterranean and 4.7 kg on low carb. 84.6 percent were still sticking with it at two years, the best in this set of studies.
DIRECT. 322 adults, two years, and the Mediterranean arm here was calorie restricted, unlike PREDIMED. Weight loss 2.9 kg low fat, 4.4 kg Mediterranean, 4.7 kg low carbohydrate. Adherence 84.6 percent at two years, the best in this evidence base.
Review of studies2020
Comparison of dietary macronutrient patterns of 14 popular named dietary programmes for weight and cardiovascular risk factor reduction in adults: systematic review and network meta-analysis
BMJ
A review pooled 121 studies with 21,942 people on popular named diets. On every diet, weight loss faded by twelve months. The gains in heart risk markers mostly disappeared by twelve months too, except on the Mediterranean diet.
121 trials, 21,942 participants. Weight loss diminished at twelve months across all macronutrient patterns and all named diets, and cardiovascular risk factor benefits essentially disappeared at twelve months for all interventions except the Mediterranean diet.

What people report

These are things people say about their own eating. Nobody checked them, so they are not evidence. They are here because they tell you what to expect and what to watch for, which the studies do not. They cannot tell you whether anything works.

The easiest diet to keep up socially and while travelling. People say this more for this diet than any other here, and the study data backs it with the best sticking-power figures.
No hunger and nothing to cut out at the start, which is why people call it a way of eating rather than a diet.
Slow or no weight loss, which lets down people who came for that. It is exactly what the studies predict.
The cost of extra virgin olive oil, nuts and fish is the most common practical complaint.
Frequent confusion about what counts, since the diet is a list of foods rather than a rule, and store-bought versions vary a lot.

Sources: How well people stuck to it in the studies, which is unusually strong here at 84.6 percent still in at two years in DIRECT, plus general nutrition forums. Unchecked self-report.

Who this is wrong for

Nobody in particular, which is unusual on this page. No specific nutrient shortfall comes with this diet.
Anyone expecting weight loss without cutting calories. PREDIMED produced almost none over five years, and the diet is high in fat and packs a lot of calories.
Anyone for whom the wine is a problem. It is part of the tested diet but not a required part, and no study has pinned down what it adds.
Anyone who reads the results as applying to them without checking who was studied. PREDIMED and CORDIOPREV both ran in Spain, where people's usual eating was already closer to this diet than a typical North American or Northern European diet. In CORDIOPREV the benefit was only in men, 67 of 414 against 94 of 413, with no difference found in the 175 women.

Questions

Was the PREDIMED trial retracted?: Yes, in 2018, and it was republished the same day. The reason was not following the study plan, not fraud. Some family members were signed up without being assigned by chance and were put in their relative's group, and assignment by chance broke down at two of eleven sites. Both halves of what came next matter. The event counts were the same, and the risk scores moved by 0.01 or not at all. But the claim that the diet caused the drop got weaker, because the new analysis leans on statistical adjustment rather than on assignment by chance alone.
Is the Mediterranean diet good for weight loss?: Only if you cut calories, and the studies make this unusually clear. PREDIMED gave no advice to cut calories and weight barely changed over five years, yet heart attacks, strokes and heart deaths still went down. DIRECT did cut calories and produced 4.4 kg of weight loss over two years. This diet's strength is heart events, not weight.
Does it actually prevent heart attacks?: It is the only diet with trial evidence on real heart attacks and strokes, and that evidence is real but comes with catches. Two studies in Spain found roughly a 28 to 31 percent lower risk. Both gave free olive oil to the diet groups, and both were partly funded by the olive oil industry. The landmark study had a problem with how people were assigned to groups. And in the study of people who already had heart disease, the benefit was only in men.
Which part of it is doing the work?: Nobody knows, because no study has tested one part on its own. It was tested as a whole diet, and in the two biggest studies the thing handed out free was olive oil or nuts. That is a reason to adopt the whole way of eating rather than to buy one ingredient.
Does it work outside the Mediterranean?: Not tested for real heart outcomes. PREDIMED and CORDIOPREV both ran in Spain, where the usual diet was already closer to this one than a typical North American or Northern European diet. That cuts an interesting way. The gap being closed there was smaller, so a bigger change elsewhere might do more, or people elsewhere might respond differently. Neither has been measured.