Mediterranean diet

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We examine the scientific evidence behind the well established Mediterranean diet and its cardiovascular benefits.

Take home messages

The Mediterranean diet is a plant-based dietary pattern made up of healthy plant foods such as whole grains, fruit and vegetables, and beans and pulses.
Olive oil is the main fat and makes up 20% of the total energy of the diet.
Meat intake is limited and fish, seafood and alcohol are consumed in moderation.
PREDIMED is a large Spanish randomised controlled trial investigating the Mediterranean diet with extra olive oil or nuts compared to a standard low-fat diet.
The Mediterranean diet has been shown to reduce the risk of CVD by 23-44%.
The benefits for cardiovascular health have been attributed to:
- improved blood lipid profiles, including a reduction in LDL cholesterol.
- reduced inflammatory markers.
- improved insulin sensitivity.
- lower BMI.
The Mediterranean diet has been shown to stop the progress of atherosclerosis and to reverse it.

What is the Med diet? Cardiovascular outcomes PREDIMED trials

The Mediterranean diet (MedDiet) reflects the dietary pattern that is traditional in the coastal Mediterranean countries in Southern Europe including Greece, Southern Italy, Spain and France^1,2. It has been associated with a lower incidence of cardiovascular disease (CVD) since the late 1950s and the publication of the Seven Countries Study^2,3.

What is the Mediterranean diet?

The MedDiet comes under the umbrella of plant-based diets and:

focusses on olive oil as the main dietary fat^4,5
promotes local fresh produce
includes high intakes of whole grains, legumes, nuts, fruit and vegetables
limits red meat to less than once a month
fish, seafood and red wine can be enjoyed in moderation
includes moderate portions of dairy foods, eggs and occasional poultry
promotes physical activity as part of its holistic approach.

The nutrient profile of the MedDiet

Like other plant-based diets, the cardiovascular advantages of the MedDiet stem from:

high intakes of nuts, plant proteins, wholegrains, fruit and vegetables
low in saturated fats, high in monounsaturated fatty acids (MUFA), low in salt, high in fibre, and rich in antioxidants and omega-3 fats
minimal intakes of red meat.

Improved CVD outcomes – what’s the evidence?

The latest report from the Greek ATTICA cohort study, with nearly 2,000 participants, found a 44% reduction in the 20-year CVD risk for those with the highest adherence to the MedDiet compared to the lowest⁶. Notably, the study found a dose-dependent effect, with benefits increasing the more people stuck to the dietary pattern.

In the larger US Women’s Health Study (which had almost 30,000 participants over 12 years), greater adherence to the MedDiet correlated with substantial reductions in CVD risk and metabolic risk factors⁷.

Compared to low adherence, those with moderate adherence had a 23% reduced CVD risk and those with high adherence had a 28% reduced CVD risk.

The biggest mediators driving CVD risk in the Women’s Health Study were identified as:

reductions in inflammatory biomarkers (accounting for 29.2% of the reduction in CVD)
improved insulin sensitivity (27.9%)
lower BMI (27.3%)
lower blood pressure (26.6%)
lower VLDL cholesterol (20.8%)
lower LDL cholesterol (13.0%).

The PREDIMED trials

A number of publications have emerged from the large multi-centre Spanish randomised intervention study known as PREDIMED (Prevención con Dieta Mediterránea, or Prevention with MedDiet)⁸. From 2003 to 2011, the study enrolled just under 7,500 men and women aged 55-80 years at high risk of CVD. The participants were randomised into three dietary groups:

MedDiet supplemented with extra virgin olive oil (50ml per day)
MedDiet supplemented with mixed nuts (30g per day)
A control (low-fat) diet.

Improved CVD outcomes

Compared to the control diet, the MedDiet significantly reduced the incidence of CVD by⁸:

31% when supplemented with extra olive oil
28% when supplemented with nuts.

Improved lipid profiles, blood pressure and glucose control

An earlier publication demonstrated that, compared to the control group, the olive oil and nut supplemented PREDIMED groups had⁹:

a significantly lower total to HDL cholesterol ratio (-0.38mmol/L and -0.26 mmol/L, respectively)
reduced blood pressure (−5.9 mm Hg and − 7.1 mm Hg, respectively)
enhanced insulin sensitivity (−0.39 mmol/L and − 0.30 mmol/L plasma glucose levels, respectively).

Reduced atherosclerosis and plaque formation

A subgroup of 164 participants in the PREDIMED trial had ultrasound assessments of internal carotid intima-media thickness (ICA-IMT) and plaque height at baseline and at 2.4 years follow up. The olive oil-supplemented group remained stable with no observed changes but the nut-supplemented group showed significant regression in ICA-IMT and reduced plaque height, while the control group exhibited progression in arterial atherosclerosis and plaque formation¹⁰.

The fat profile of the PREDIMED diet is key to reducing CVD risk

It is noteworthy that the PREDIMED Diet was not low in fat yet demonstrated greater cardio-protection than the low-fat control diet. The fat content is characterised by low saturated fat (SFA) (9.1% to 9.4% of energy) and high MUFA (makes up 20% of total energy intake). This fat profile has been proven to improve blood lipid levels and to be protective against CVD^11,12.

Nutrient intakes with the PREDIMED diet compared to control diet at the end of the trial⁸

	Control diet		MeDiet + extra virgin olive oil		MeDiet + nuts
	n=1,941		n=2,364		n=2,108
	Mean	SD	Mean	SD	Mean	SD
Energy (kcal)	1,960	±497	2,175	±475	2,229	±477
Protein g/d	17.1	±3.0	16.2	±2.4	16.4	±2.5
Total carbs (% E)	43.7	±7.0	40.4	±5.9	39.7	±6.3
Fibre (g/d)	23.7	±7.7	25.4	±7.5	27.0	±8.0
Total fat (%E)	37.0	±7.0	41.2	±5.4	41.5	±6.1
Saturated fat (%E)	9.1	±2.1	9.4	±2.0	9.3	±2.0
MUFA (%E)	18.8	±4.6	22.1	±3.7	20.9	±4.1
PUFA (%E)	5.5	±1.7	6.1	±1.4	7.7	±1.8
n-6 LA (g/d)	10.0	±4.8	12.22	±4.6	16.0	±5.5
n-3 ALA (g/d)	1.1	±0.5	1.3	±0.7	1.9	±0.7
EPA/DHA (g/d)	0.7	±0.4	0.9	±0.5	0.8	±0.5
Olive oil (%E)	16.4	±6.8	22.0	±6.0	17.6	±6.4
Nuts (%E)	1.6	±2.5	2.6	±3.1	8.2	±4.5
Cholesterol	32	±10	339	±101	338	±99

SD = standard deviation, g/d = grammes per day; %E = percentage of total energy intake
MUFA = monounsaturated fatty acids; PUFA = polyunsaturated fatty acids
EPA = omega-3 Eicosapentaenoic acid from fish oils; DHA = omega-3 Docosahexaenoic acid from fish oils

In summary

Traditional Mediterranean-style diets come under the ‘plant-based diet’ umbrella. They prioritise healthy plant foods while minimising meat intakes, promote eating nuts every day, and olive oil is the main fat. A substantial body of evidence from intervention trials and large cohort studies shows that a greater adherence to the MedDiet leads to enhanced metabolic health and lower cardiovascular risk. Notably, these benefits accumulate incrementally, allowing individuals to make gradual, realistic changes while still gaining benefits for their health.

References

Mastorakou D, Rabaeus M, Salen P, Pounis G, de Lorgeril M. Chapter 9 - Mediterranean Diet: A Health-Protective Dietary Pattern for Modern Times. In: Pounis G, ed. Analysis in Nutrition Research. Academic Press; 2019:233-258. doi:10.1016/B978-0-12-814556-2.00009-9
Finicelli M, Di Salle A, Galderisi U, Peluso G. The Mediterranean Diet: An Update of the Clinical Trials. Nutrients. 2022;14(14):2956. doi:10.3390/nu14142956
KEYS A, MIENOTTI A, KARVONEN MJ, et al. THE DIET AND 15-YEAR DEATH RATE IN THE SEVEN COUNTRIES STUDY. American Journal of Epidemiology. 1986;124(6):903-915. doi:10.1093/oxfordjournals.aje.a114480
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;378(25):e34. doi:10.1056/NEJMoa1800389
Ros E. The PREDIMED study. Endocrinología, Diabetes y Nutrición. 2017;64(2):63-66. doi:10.1016/j.endinu.2016.11.003
Georgoulis M, Damigou E, Chrysohoou C, et al. Mediterranean diet trajectories and 20-year incidence of cardiovascular disease: The ATTICA cohort study (2002-2022). Nutr Metab Cardiovasc Dis. 2024;34(1):153-166. doi:10.1016/j.numecd.2023.09.019
Ahmad S, Moorthy MV, Demler OV, et al. Assessment of Risk Factors and Biomarkers Associated With Risk of Cardiovascular Disease Among Women Consuming a Mediterranean Diet. JAMA Netw Open. 2018;1(8):e185708. doi:10.1001/jamanetworkopen.2018.5708
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;378(25):e34. doi:10.1056/NEJMoa1800389
Estruch R, Martínez-González MA, Corella D, et al. Effects of a Mediterranean-style diet on cardiovascular risk factors: a randomized trial. Ann Intern Med. 2006;145(1):1-11. doi:10.7326/0003-4819-145-1-200607040-00004
Sala-Vila A, Romero-Mamani ES, Gilabert R, et al. Changes in ultrasound-assessed carotid intima-media thickness and plaque with a Mediterranean diet: a substudy of the PREDIMED trial. Arterioscler Thromb Vasc Biol. 2014;34(2):439-445. doi:10.1161/ATVBAHA.113.302327
SACN. Saturated fats and health. GOV.UK. Published August 2019. Accessed October 16, 2023. https://www.gov.uk/government/publications/saturated-fats-and-health-sacn-report
Visseren FLJ, Mach F, Smulders YM, et al. 2021 ESC Guidelines on cardiovascular disease prevention in clinical practice: Developed by the Task Force for cardiovascular disease prevention in clinical practice with representatives of the European Society of Cardiology and 12 medical societies With the special contribution of the European Association of Preventive Cardiology (EAPC). European Heart Journal. 2021;42(34):3227-3337. doi:10.1093/eurheartj/ehab484

Published: June 2024