Cardiovascular diseases (CVDs) are the number one cause of death globally.¹ The World Health Organization (WHO) predicts that the number of CVD-associated deaths will increase to reach a staggering 23.3 million by 2030, and that CVDs will remain the single leading cause of death worldwide.² Due to such a profound impact of CVDs on population health, numerous research studies have focused on identifying effective heart disease prevention measures. It has been postulated that behavioral risk factors account for about 80% of coronary heart disease and cerebrovascular disease,¹ indicating that dietary and lifestyle patterns play a pivotal role in their prevention. In the sea of bad news surrounding CVDs, this, in fact, is a piece of good news.

Exercising regularly, avoiding tobacco use, and following a healthy diet are effective measures aimed at warding off heart disease. But what exactly falls under the broad definition of a healthy diet, what are its key ingredients, and what is their mechanism of action? While other plant-based diets may exert similar protective effects, this article will present a brief overview of several important studies correlating the Mediterranean diet with heart health.

The main ingredients of the Mediterranean diet are fruits and vegetables, legumes, nuts and cereals, olive oil and fish. Low-to-moderate intake of dairy products and red meat, and moderate intake of wine with meals, are also typical for the Mediterranean diet.³ A study published in 2003 in the New England Journal of Medicine followed 22,043 adults in Greece during a median period of 44 months.⁴ The study found that a high degree of adherence to the Mediterranean diet, assessed on a scale of 0 to 9, was associated with an overall reduction in total mortality during the 44 month follow-up period. In addition, greater adherence to this diet was inversely associated with death due to coronary disease and death due to cancer.

Another large, multicenter, nutritional intervention study, termed the PREDIMED study, was launched in Spain in 2003. This randomized trial followed 7447 persons in the age range 55-80 years, from 2003 to 2011, with the aim of investigating the effects of the Mediterranean diet on prevention of major cardiovascular events in high-risk persons. Study participants were divided into three dietary intervention groups: a low-fat diet group, a Mediterranean diet group supplemented with extra-virgin olive oil, and a Mediterranean diet group supplemented with tree nuts (walnuts, almonds, hazelnuts). The main finding of this large trial was that the Mediterranean diet supplemented with extra-virgin olive oil or tree nuts reduced the risk of suffering from CVD-related death, myocardial infarction or stroke by approximately 30 percent.⁵

Although a positive correlation between the Mediterranean diet and heart health has been established, less information is available on the mechanism by which this diet exerts its effects.  In which segment of the long cascade of events leading to CVD does the Mediterranean diet exert protection? Atherosclerosis is a slow, progressive, inflammatory disease that starts with injury to the arterial wall and, over time, leads to the build-up of cholesterol-filled plaques in the inner lining of the artery. Arterial hardening and narrowing follows, causing obstructed blood flow. Accumulation of inflammatory cells at the site of injury is an important step in this process, thus, assessment of the biomarkers of inflammation can indicate disease progression and plaque instability.

A recent study investigated the effects of the Mediterranean diet on biomarkers of inflammation and plaque instability in persons with high risk for CVD.⁶ One hundred sixty four subjects were included in the study and randomized into three diet groups as follows: a low-fat diet group, a Mediterranean diet group supplemented with extra-virgin olive oil, and a Mediterranean diet group supplemented with tree nuts. After 12 months of intervention, changes in inflammatory biomarkers and plaque vulnerability were measured.  A significant decrease in inflammatory biomarkers was observed in subjects adhering to the Mediterranean diet supplemented with extra virgin olive oil or nuts, in addition to a reduction in cardiovascular risk factors such as blood pressure, and LDL- and total cholesterol levels. It appears that the Mediterranean diet exerts its effect at least at two levels, although additional mechanistic studies are necessary to draw any final conclusions.

The peoples occupying the Mediterranean region, such as Sicilians, have been known for their good health and longevity, and although the Mediterranean diet is not the only influencing factor, it is likely one of the more significant ones. ⁷ The good news is that it may never be too late to make in change in one’s dietary habits. Positive effects in the main cardiovascular risk factors have been observed only three months after implementing a supplemented Mediterranean diet in persons at high cardiovascular risk, aged 55 to 80 years.⁸ With this in mind, you just might discover new appreciation for the distinct flavor and aroma of olive oil.

References

1. Global status report on noncommunicable diseases 2010. Geneva, World Health Organization, 2011.
2. Mathers CD, Loncar D. Projections of global mortality and burden of disease from 2002 to 2030.PLoS Med. 2006; 3(11):e442.
3. Willett WC, Sacks F, Trichopoulou A, et al. Mediterranean diet pyramid: a cultural model for healthy eating. Am J Clin Nutr. 1995; 61:Suppl 6:S1402-S1406.
4. Trichopoulou A, Costacou T, Bamia C, et al. Adherence to a Mediterranean Diet and Survival in a Greek Population. N Engl J Med. 2003; 348(26):2599-2608.
5. Estruch R, Ros E, Salas-Salvadó J, et al. Primary Prevention of Cardiovascular Disease with Mediterranean Diet. N Engl J Med. 2013; 368(14):1270-90.
6. Casas R, Sacanella E, Urpi-Sarda M, et al. The Effects of the Mediterranean Diet on Biomarkers of Vascular Wall Inflammation and Plaque Vulnerability in Subjects with High Risk for Cardiovascular Disease. A Randomized Trial. Plos One. 2014; 9(6):1-11.
7. Vasto S, Scapagnini G, Rizzo C, et al. Mediterranean diet and longevity in Sicily: survey in a Sicani Mountains population. Rejuvenation Res. 2012;15(2):184-8.
8. 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.

Jasenka Piljac Zegarac is a scientist and freelance writer. She holds a PhD in biology and a BS degree in biochemistry, and contributes on a regular basis to several health and science blogs. Her scientific publications have gathered more than 1100 citations. She may be contacted for assistance with a variety of science and medical writing projects.