The American College of Cardiology (ACC) and American Heart Association (AHA) recommend a heart-healthy dietary pattern for everyone, but especially for people at risk for atherosclerotic cardiovascular disease (ASCVD).2-4 In fact, the 2019 ACC/AHA Guideline on the Primary Prevention of Cardiovascular Disease specifically mentions the Mediterranean diet as a heart-healthy eating pattern. In general, a heart-healthy diet can lower risk factors for ASCVD such as high cholesterol and high blood pressure. The caloric intake should be limited to prevent weight gain in normal-weight people and promote weight loss in overweight or obese people.
The diet should include:
- Fruits
- Vegetables
- Whole grains
- Beans and legumes
- Healthy protein sources (low-fat dairy products, low-fat poultry (with no skin), fish, seafood, and nuts)
- Non-tropical vegetable oils
The diet should limit:
- Sweets
- Sugar-sweetened beverages
- Red meats
- Processed red meats (such as bacon, salami, ham, hot dogs, sausage)
Mediterranean Diet and Cardiovascular Disease
A 2019 Cochrane Review1 made a thorough search and analysis of studies. It identified 30 RCTs on the effectiveness of the Mediterranean diet for primary and secondary prevention of cardiovascular disease (CVD). Unfortunately, the majority of these studies did not meet the criteria for inclusion due to study design or the unreliability of data. They found that none of the nine trials that studied the Mediterranean diet versus no or minimal intervention for primary prevention reported clinical CVD events.
They only found one trial that met the analysis criteria for primary prevention of CVD where the Mediterranean diet was compared against another dietary intervention.1 The PREDIMED trial,5 first reported in 2013, studied 7447 people in Spain at high risk for CVD comparing the Mediterranean diet vs a low-fat diet. The authors of the Cochrane Review looked at the 2018 re-analyzed report6 (n=5859) where the authors accounted for some issues with randomization from two sites that were included in the first report. They found a reduced risk of stroke (HR 0.60, 95% CI [0.45 – 0.80], moderate-quality evidence), but no significant reduction of risk of heart attack (HR 0.79, 95% CI [0.57 – 1.10], low-quality evidence)), CVD-related death (HR 0.81, 95% CI [0.50 – 1.32], low-quality evidence), or all-cause mortality (HR 1.0, 95% CI [0.81 – 1.24], low-quality evidence).1
The Cochrane Review1 found one study that examined the Mediterranean diet versus usual care for secondary prevention of CVD events, the Lyon Diet Heart Study. The Lyon Diet Heart Study followed 605 participants (<70 years old; 90% male) who had survived one myocardial infarction (MI).7 They were randomly split into two groups. The control group (n=303) received no dietary education beyond the prudent instructions of their physicians.8 The experimental group (n=302) received individualized diet plans based on the Mediterranean diet that were adjusted to fit the individuals’ gastronomic preferences, eating schedules, and financial resources. Investigators regularly followed up with the experimental group, re-instructed them, and assessed compliance. When this study was analyzed by the Cochrane authors, they found reductions in total mortality (HR 0.44, 95% CI [0.21 – 0.92], moderate-quality evidence), CVD mortality (HR 0.35, 95% CI [0.15 – 0.82], low-quality evidence) and the combined clinical endpoints of CVD death and non-fatal MI (HR 0.28, 95% CI [0.15 – 0.52]).
The authors found one small study that met analysis criteria for the Mediterranean diet versus another dietary intervention for secondary prevention.1 Tuttle et al. performed a trial on first MI survivors randomizing them to a Mediterranean diet (n=51 or a low-fat diet (n=50) compared to 101 matched controls with no dietary intervention.9 The main difference between the diets was the Mediterranean diet had a higher omega-3 fat intake. They found that low-fat and Mediterranean diets have similar and significant benefits for CVD-event-free survival after an MI compared to usual care. However, the Cochrane Review analysis found that the data for the dietary interventions versus the controls showed “considerable uncertainty in the effect size” when they analyzed the all-cardiac clinical endpoints (MI, hospital admissions for heart failure, unstable angina, stroke, and all-cause and cardiac mortality) with an RR of 0.98 (95% CI, [0.40 – 2.41], very low-quality evidence).1
It is unclear exactly which component of the Mediterranean diet is responsible for the cardioprotective effects. Olive oil, nuts, fruits, legumes, and vegetables have all been proposed.10,11 According to one meta-analysis, the pooled data from prospective cohort studies showed that only dairy products (which are largely excluded from a Mediterranean diet) significantly increase the risk of CVD, increasing the RR to 1.10 (95% CI [1.02 – 1.19], I2=49%).10
One shortcoming of the current evidence on the effects of the Mediterranean diet is that, so far, the largest, reliable randomized controlled trials on the diet have been completed in Mediterranean populations. This raises questions about the transferability of the diet to non-Mediterranean persons. However, prospective cohort studies completed in non-Mediterranean countries provide evidence that the diet is still effective in lowering the risk of CVD. According to one meta-analysis, the RR for CVD in this subgroup is 0.77 (95% CI [0.70 – 0.83]).10 Additionally, one of the principal investigators on the PREDIMED trial is confident in the transferability of the diet, if applied correctly.12 To that end, some have proposed that the current methods of assessing adherence to the diet should be modified when the diet is applied in non-Mediterranean countries.13 In sum, the Mediterranean diet is widely acknowledged to reduce the risk of both primary and recurrent CVD.
References
- Rees K, Takeda A, Martin N, et al. Mediterranean-style diet for the primary and secondary prevention of cardiovascular disease. Cochrane Database Syst Rev 2019; 3: Cd009825.
- Grundy SM, Stone NJ, Bailey AL, et al. 2018 AHA/ACC/AACVPR/AAPA/ABC/ACPM/ADA/AGS/APhA/ASPC/NLA/PCNA guideline on the management of blood cholesterol. A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines 2018: 25709.
- Whelton PK, Carey RM, Aronow WS, et al. 2017 ACC/AHA/AAPA/ABC/ACPM/AGS/APhA/ASH/ASPC/NMA/PCNA guideline for the prevention, detection, evaluation, and management of high blood pressure in adults: executive summary: a report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines. Hypertension 2017.
- Arnett DK, Blumenthal RS, Albert MA, et al. 2019 ACC/AHA guideline on the primary prevention of cardiovascular disease: a report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines. Circulation 2019; 140 (11): e596-e646.
- Estruch R, Ros E, Salas-Salvadó J, et al. RETRACTED ARTICLE: Primary prevention of cardiovascular disease with a Mediterranean diet. N Engl J Med 2013; 368 (14): 1279-1290.
- 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. N Engl J Med 2018; 378 (25): e34.
- 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; 99 (6): 779-785.
- de Lorgeril M, Salen P, Caillat-Vallet E, et al. Control of bias in dietary trial to prevent coronary recurrences: The Lyon Diet Heart Study. Eur J Clin Nutr 1997; 51 (2): 116-122.
- Tuttle KR, Shuler LA, Packard DP, et al. Comparison of low-fat versus Mediterranean-style dietary intervention after first myocardial infarction (from The Heart Institute of Spokane Diet Intervention and Evaluation Trial). Am J Cardiol 2008; 101 (11): 1523-1530.
- Grosso G, Marventano S, Yang J, et al. A comprehensive meta-analysis on evidence of Mediterranean diet and cardiovascular disease: Are individual components equal? Critical Reviews in Food Science and Nutrition 2017; 57 (15): 3218-3232.
- Estruch R, Ros E, Salas-Salvado J, et al. Primary prevention of cardiovascular disease with a Mediterranean diet. N Engl J Med 2013; 368 (14): 1279-1290.
- Martínez-González M, Hershey MS, Zazpe I, et al. Transferability of the Mediterranean diet to non-Mediterranean countries. what is and what is not the Mediterranean diet. Nutrients 2017; 9 (11).
- Hoffman R, Gerber M. Evaluating and adapting the Mediterranean diet for non-Mediterranean populations: a critical appraisal. Nutrition Reviews 2013; 71 (9): 573-584.
