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Research · Diets

Mediterranean diet

In trials of adults at high heart risk, a Mediterranean diet with olive oil or nuts was followed by fewer heart attacks, strokes and cardiovascular deaths than low-fat or minimal advice, though reviews differ on certainty. Weight loss matched most other diets. Cognition results were mixed. Trials reported few, minor harms and no weight gain.

Add to Bio HackChecked 2026-11-13
Status
A dietary pattern, not a regulated product.
Also called
Med diet, MedDiet, Mediterranean-style diet, PREDIMED diet, Mediterranean eating pattern
Followed for
heart health, heart attack and stroke prevention, diabetes prevention, blood sugar, weight loss, blood pressure, cholesterol, brain health, longevity

Strong several reviews agree · Moderate one review or consistent trials · Limited one or a few small studies · Untested no study in people, listed with what it rests on

Shown to help4

Reported risks0

No risks sourced yet.

What people follow it for, and what was found

Shown to help4

Moderate

Heart attack, stroke and cardiovascular death

Shown to lower heart attacks, strokes and cardiovascular deaths against minimal advice in adults at raised heart risk, with reviews disagreeing on how certain this is.

Compared with minimal intervention, such as a healthy diet brochure, and low-fat programmes, in a network meta-analysis [1]; a low-fat diet in the PREDIMED trial, and usual care in the Lyon Diet Heart Study [2]; a control diet of advice to reduce dietary fat, in Spanish adults [3]; a low-fat diet, in patients with coronary heart disease [4]; a prudent Western-type diet, in patients after a first heart attack [5]

The numbers and sources
Effect
In a network meta-analysis of 40 trials (35,548 people), Mediterranean programs lowered all-cause death (OR 0.72, 95% CI 0.56 to 0.92), cardiovascular death (OR 0.55, 95% CI 0.39 to 0.78), stroke (OR 0.65, 95% CI 0.46 to 0.93) and non-fatal heart attack (OR 0.48, 95% CI 0.36 to 0.65) against minimal intervention, at moderate certainty. Mediterranean and low-fat programs did not clearly differ for death or non-fatal heart attack [1]. A Cochrane review found low-quality evidence of little or no effect of the PREDIMED diets against a low-fat diet on cardiovascular death (HR 0.81, 95% CI 0.50 to 1.32) or total death (HR 1.0, 95% CI 0.81 to 1.24), and fewer strokes (HR 0.60, 95% CI 0.45 to 0.80, moderate quality) [2]. In PREDIMED, major cardiovascular events occurred in 3.8% on the olive oil diet, 3.4% on the nut diet and 4.4% on the low-fat control diet over a median 4.8 years (HR 0.69, 95% CI 0.53 to 0.91, and HR 0.72, 95% CI 0.54 to 0.95) [3]. In CORDIOPREV, events ran at 28.1 per 1,000 person-years on the Mediterranean diet against 37.7 on a low-fat diet over 7 years (adjusted HR 0.719 to 0.753) [4]. In the Lyon Diet Heart Study, cardiac death plus non-fatal heart attack totaled 14 events on a Mediterranean-type diet against 44 on a prudent Western-type diet over a mean 46 months [5].
Population
Adults at raised cardiovascular risk in 40 trials followed at least 9 months [1]; 30 RCTs with 12,461 people [2]; 7,447 Spanish adults aged 55 to 80 at high risk with no heart disease at entry [3]; 1,002 patients with coronary heart disease, 82.5% men [4]; 605 patients after a first heart attack [2][5].
Sources
[1], [2], [3], [4], [5]
Caveats
PREDIMED's first report was withdrawn after randomization problems at 2 of 11 sites. The reanalysis gave similar results after leaving out 1,588 affected participants [3]. The Cochrane review rated the death evidence low quality and the network meta-analysis rated it moderate [1][2]. In CORDIOPREV the effect appeared in men, and no difference was found in the 175 women [4]. CORDIOPREV was funded in part by olive oil foundations [4]. The Lyon trial added canola margarine and compared against usual care, and the Cochrane review rated it low quality [2].
Moderate

Weight

Shown to lower weight about 1.75 kg against control diets in adults, more with calorie restriction or exercise, and to match low-carbohydrate and diabetes association diets.

Compared with control diets the source does not describe [6]; a low-fat diet, a low-carbohydrate diet and the American Diabetes Association diet [7]; a control diet of advice to reduce dietary fat, in Spanish adults [8]; ad libitum Mediterranean diet advice, so both groups ate a Mediterranean diet [9]

The numbers and sources
Effect
Across 16 RCTs (3,436 participants), the Mediterranean diet lowered weight by 1.75 kg against control diets (95% CI -2.86 to -0.64). The difference was 3.88 kg with energy restriction, 4.01 kg with more physical activity and 2.69 kg with follow-up past 6 months [6]. In 5 RCTs lasting 12 months or more (998 participants), mean weight change ranged from 4.1 to 10.1 kg lost on the Mediterranean diet against a range from 2.9 kg gained to 5.0 kg lost on low-fat diets, and weight loss was similar to low-carbohydrate and American Diabetes Association diets [7]. In PREDIMED, with no calorie limit, the 5-year weight change did not differ from the low-fat control (olive oil -0.41 kg, 95% CI -0.83 to 0.01, nuts -0.02 kg, 95% CI -0.45 to 0.42) [8]. In PREDIMED-Plus, an energy-reduced Mediterranean diet with exercise and behavioral support lost 3.2 kg at 12 months against 0.7 kg on ad libitum Mediterranean advice (difference -2.5 kg, 95% CI -3.1 to -1.9) [9].
Population
Adults in 16 trials [6]; adults with overweight or obesity trying to lose weight [7]; older Spanish adults at high cardiovascular risk [8]; 626 adults aged 55 to 75 with overweight or obesity and metabolic syndrome [9].
Sources
[6], [7], [8], [9]
Caveats
The added weight loss in [6] grew when calories were cut or exercise was added, so the diet alone accounts for part of it. In PREDIMED-Plus both groups ate a Mediterranean diet, so the difference reflects calorie reduction, exercise and support [9].
Moderate

Blood pressure, cholesterol and blood sugar markers

Shown to lower blood pressure about 3/2 mmHg and LDL cholesterol and HbA1c slightly in adults, at low to moderate certainty.

Compared with no or minimal intervention, and another dietary intervention the abstract does not name [2]; a low-fat diet, a low-carbohydrate diet and the American Diabetes Association diet [7]; control diets the source does not describe [10]

The numbers and sources
Effect
Against no or minimal intervention, systolic blood pressure fell 2.99 mmHg (95% CI -3.45 to -2.53) and diastolic 2.0 mmHg (95% CI -2.29 to -1.71) at moderate quality, with little or no effect on LDL or HDL. Against other diets, LDL fell 0.15 mmol/L (95% CI -0.27 to -0.02) and triglycerides 0.09 mmol/L, with little or no effect on blood pressure [2]. In 9 RCTs (1,337 people at raised risk of diabetes or heart disease), HbA1c fell 0.18 points (95% CI -0.35 to -0.01), LDL 0.10 mmol/L and triglycerides 0.20 mmol/L. Fasting glucose, insulin, insulin resistance and HDL did not change [10]. Over 12 months or more, blood pressure and lipids changed about as much as on comparator diets [7].
Population
Healthy adults and adults at high cardiovascular risk [2]; adults at increased risk of type 2 diabetes and heart disease [10]; adults with overweight or obesity [7].
Sources
[2], [7], [10]
Caveats
The Cochrane review rated the lipid evidence low or very low quality for most comparisons [2]. The changes are small next to drug effects.
Limited

Type 2 diabetes onset

One large trial found fewer new diabetes cases on the olive oil Mediterranean diet, and cohorts link closer adherence to lower diabetes risk.

Compared with a control diet of advice on a low-fat diet [11]; people with lower Mediterranean diet adherence scores, per 2 points, in 24 cohorts, and a low-fat diet in the one trial (PREDIMED) [12]; ad libitum Mediterranean diet advice, without calorie reduction or added exercise [13]

The numbers and sources
Effect
In 3,541 PREDIMED participants without diabetes, new diabetes ran at 16.0 cases per 1,000 person-years on the olive oil diet, 18.7 on the nut diet and 23.6 on the low-fat control over a median 4.1 years (HR 0.60, 95% CI 0.43 to 0.85, and HR 0.82, 95% CI 0.61 to 1.10) [11]. In 24 cohorts and 1 RCT (991,878 participants), each 2-point rise in adherence score was linked to 8% lower diabetes risk (HR 0.92, 95% CI 0.90 to 0.94, moderate certainty) [12]. In PREDIMED-Plus, adding a 600 kcal a day reduction, exercise and weight-loss support to a Mediterranean diet cut 6-year diabetes incidence by 31% (95% CI 18% to 41%) against ad libitum Mediterranean advice, 9.5% against 12.0% [13].
Population
Spanish adults aged 55 to 80 at high cardiovascular risk [11]; adults in cohorts, observational [12]; 4,746 adults aged 55 to 75 with metabolic syndrome and overweight or obesity [13].
Sources
[11], [12], [13]
Why limited
This rests on one trial, of 3,541 people. Strength counts independent studies that agree, so one trial is limited at any size.
Caveats
The PREDIMED result is a subgroup analysis, randomization was not stratified by diabetes status and withdrawals were higher in the control group [11]. The nut diet result was not significant [11]. The cohort data are observational [12]. PREDIMED-Plus compared two Mediterranean diets, so it tests calorie reduction and exercise, not the Mediterranean pattern itself [13].

Mixed results1

Limited

Cognition and dementia

Mixed results: one trial found better cognitive composite scores, most other trial outcomes did not differ, and two cohort meta-analyses found no significant dementia link.

Compared with a control diet of advice to reduce dietary fat [14]; an alternate diet the abstract does not describe [15]; people with the lowest Mediterranean diet adherence, in cohorts [16], [17]

The numbers and sources
Effect
In 334 PREDIMED participants retested after a median 4.1 years, the olive oil diet scored better on global and frontal composites and the nut diet on memory against a low-fat control, while all composites fell in the control group [14]. Across 5 RCTs (1,888 participants), only 8 of 66 cognitive outcomes favored a Mediterranean diet, 2 favored controls, and no trial found less cognitive impairment or dementia [15]. In cohort meta-analyses, high adherence was not significantly linked to dementia risk (HR 0.85, 95% CI 0.71 to 1.03 [16], HR 0.90, 95% CI 0.78 to 1.05 [17]).
Population
Cognitively healthy adults with a mean age of 66.9 at high cardiovascular risk [14]; adults in 5 RCTs [15]; older adults in prospective cohorts, observational [16][17].
Sources
[14], [15], [16], [17]
Caveats
The review could not pool the trials [15]. The prescribed diets varied a lot between trials [15]. Within one cohort meta-analysis, the link reached significance in studies following people 10 years or less (HR 0.72) [16].

How trials defined it

Reviews defined a Mediterranean-style diet by two required features: a high ratio of monounsaturated to saturated fat, with olive oil as the main cooking fat or tree nuts, and a high intake of fruits, vegetables and legumes. Optional features were low to moderate red wine, whole grains, less meat, more fish and moderate dairy [2]. PREDIMED gave extra-virgin olive oil (1 L a week) or mixed nuts (30 g a day) with quarterly education sessions, against advice to cut dietary fat, with no calorie limit and no exercise advice [3][8][14]. PREDIMED-Plus planned a 600 kcal a day reduction with more physical activity, against ad libitum Mediterranean advice [13]. CORDIOPREV used dietitian-led Mediterranean or low-fat diets for 7 years [4]. The Lyon trial used a Mediterranean-type diet with canola margarine against usual care [2][5].

Risks

Checked, no increase found2

Moderate

Weight gain from the added fat

Not shown to raise weight in adults, even with no calorie limit and added olive oil or nuts.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
No trial in a 16-trial meta-analysis reported significant weight gain on a Mediterranean diet [6]. In PREDIMED, 5-year weight change did not differ from a low-fat control, and waist growth was 0.92 cm smaller on the nut diet (95% CI -1.60 to -0.24) [8].
Population
Adults in 16 RCTs [6]; 7,447 older Spanish adults at high cardiovascular risk [8].
Sources
[6], [8]
Caveats
PREDIMED was funded in part by olive oil and nut producers [8]. Waist grew in all three PREDIMED groups [8].
Limited

Adverse events in trials

Limited evidence: two trials reporting adverse events found none or only minor ones.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
Of 30 trials in a Cochrane review, two reported adverse events, which were absent or minor [2].
Population
Trial participants in primary and secondary prevention [2].
Sources
[2]
Caveats
Low to moderate quality evidence. Most trials did not report harms [2].

Claims tested and not found

  1. That the fat in a Mediterranean diet causes weight gain. No trial in a 16-trial meta-analysis reported significant weight gain, and PREDIMED found no weight difference from a low-fat diet over 5 years [6][8].
  2. That a Mediterranean diet lowers dementia risk. No trial in a 5-trial review found less dementia or cognitive impairment, and two cohort meta-analyses found no significant link [15][16][17].

Sources

  1. Karam G, Agarwal A, Sadeghirad B, et al. Comparison of seven popular structured dietary programmes and risk of mortality and major cardiovascular events in patients at increased cardiovascular risk: systematic review and network meta-analysis. BMJ. 2023. https://doi.org/10.1136/bmj-2022-072003
  2. Rees K, Takeda A, Martin N, et al. Mediterranean-style diet for the primary and secondary prevention of cardiovascular disease. Cochrane Database of Systematic Reviews. 2019. https://doi.org/10.1002/14651858.CD009825.pub3
  3. Estruch R, Ros E, Salas-Salvadó J, et al. Primary Prevention of Cardiovascular Disease with a Mediterranean Diet Supplemented with Extra-Virgin Olive Oil or Nuts. New England Journal of Medicine. 2018. https://doi.org/10.1056/NEJMoa1800389
  4. Delgado-Lista J, Alcala-Diaz JF, Torres-Peña JD, et al. Long-term secondary prevention of cardiovascular disease with a Mediterranean diet and a low-fat diet (CORDIOPREV): a randomised controlled trial. The Lancet. 2022. https://doi.org/10.1016/S0140-6736(22)00122-2
  5. de Lorgeril M, Salen P, Martin JL, et al. Mediterranean diet, traditional risk factors, and the rate of cardiovascular complications after myocardial infarction: final report of the Lyon Diet Heart Study. Circulation. 1999. https://doi.org/10.1161/01.CIR.99.6.779
  6. Esposito K, Kastorini CM, Panagiotakos DB, et al. Mediterranean diet and weight loss: meta-analysis of randomized controlled trials. Metabolic Syndrome and Related Disorders. 2011. https://doi.org/10.1089/met.2010.0031
  7. Mancini JG, Filion KB, Atallah R, et al. Systematic Review of the Mediterranean Diet for Long-Term Weight Loss. The American Journal of Medicine. 2016. https://doi.org/10.1016/j.amjmed.2015.11.028
  8. Estruch R, Martínez-González MA, Corella D, et al. Effect of a high-fat Mediterranean diet on bodyweight and waist circumference: a prespecified secondary outcomes analysis of the PREDIMED randomised controlled trial. The Lancet Diabetes & Endocrinology. 2019. https://doi.org/10.1016/S2213-8587(19)30074-9
  9. Salas-Salvadó J, Díaz-López A, Ruiz-Canela M, et al. Effect of a Lifestyle Intervention Program With Energy-Restricted Mediterranean Diet and Exercise on Weight Loss and Cardiovascular Risk Factors: One-Year Results of the PREDIMED-Plus Trial. Diabetes Care. 2019. https://doi.org/10.2337/dc18-0836
  10. Lauria F, Formisano A, Dello Russo M, et al. Mediterranean diet, gut microbiota, and type 2 diabetes: A systematic review and meta-analysis of intervention trials. Nutrition, Metabolism and Cardiovascular Diseases. 2026. https://doi.org/10.1016/j.numecd.2025.104433
  11. Salas-Salvadó J, Bulló M, Estruch R, et al. Prevention of diabetes with Mediterranean diets: a subgroup analysis of a randomized trial. Annals of Internal Medicine. 2014. https://doi.org/10.7326/M13-1725
  12. Wallerer S, Stadelmaier J, Floegel E, et al. Adherence to Mediterranean Diet and Risk of Type 2 Diabetes: An Updated Systematic Review and Dose-Response Meta-analysis. Advances in Nutrition. 2025. https://doi.org/10.1016/j.advnut.2025.100562
  13. Ruiz-Canela M, Corella D, Martínez-González MÁ, et al. Comparison of an Energy-Reduced Mediterranean Diet and Physical Activity Versus an Ad Libitum Mediterranean Diet in the Prevention of Type 2 Diabetes: A Secondary Analysis of a Randomized Controlled Trial. Annals of Internal Medicine. 2025. https://doi.org/10.7326/ANNALS-25-00388
  14. Valls-Pedret C, Sala-Vila A, Serra-Mir M, et al. Mediterranean Diet and Age-Related Cognitive Decline: A Randomized Clinical Trial. JAMA Internal Medicine. 2015. https://doi.org/10.1001/jamainternmed.2015.1668
  15. Radd-Vagenas S, Duffy SL, Naismith SL, et al. Effect of the Mediterranean diet on cognition and brain morphology and function: a systematic review of randomized controlled trials. The American Journal of Clinical Nutrition. 2018. https://doi.org/10.1093/ajcn/nqx070
  16. Wang Y, Lin X, Cheng L, et al. Dietary Patterns and Risk of Dementia in Elderly Individuals: A Systematic Review and Meta-analysis of Cohort Studies. Nutrition Reviews. 2026. https://doi.org/10.1093/nutrit/nuaf121
  17. Kim Y, Kim Y. The association of seven dietary patterns and the risk of dementia: a systematic review and meta-analysis of prospective cohort studies. Psychiatry Research. 2027. https://doi.org/10.1016/j.psychres.2026.117531

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