Definition, foods, and health benefits of the mediterranean diet

The concept of mediterranean diet was developed in the 1950’s by the American physiologist Ancel Benjamin Keys.
Keys first described the relationship between diet and cardiovascular diseases or CVD, in particular thanks to the epidemiological study known as the Seven Countries Study, the first study that highlighted the mediterranean dietary pattern.
The Mediterranean diet, which is recognized as one of the healthiest dietary pattern, is rich in minimally processed plant foods, such as vegetables, legumes, cereals, preferably whole grain, with extra virgin olive oil as the main source of lipids. Therefore, it is a dietary pattern rich in antioxidant compounds, and with anti-inflammatory action.
The Seven Country Study was followed by many other studies that  highlighted, in populations of industrialized and non-industrialized countries, the protective role of this dietary pattern not only on CVD but also chronic-degenerative diseases, depressive disorders, as well as a correlation with improvements in learning ability. And it has been shown that greater adherence to the mediterranean diet is associated with improved health status and reduced mortality in general.
For all this, there is no scientific association that support that it is harmful for health.
In addition, thanks to the reduced consumption of meat, mediterranean diet improve public health by contributing to the reduction of greenhouse gas emissions.
Ultimately, the mediterranean diet is a dietary pattern that must be safeguarded and promoted, as opposed to the worldwide trends toward dietary uniformity.

CONTENTS

Ancel Keys and the Seven Countries Study

Keys identified the correlation between diet and cardiovascular disease risk in the early 1950s by comparing the rate of CVD occurrence of American business executives, and European populations just out of World War II. While in the former, well nourished subjects, the onset rates were high, in the latter, who were in a phase of food insecurity, the rates were low. These observations led Keys to hypothesize a correlation between dietary fat intake and deaths from cardiovascular diseases.
The subsequent observation of an extremely low frequency of coronary heart disease and certain cancers in the population of the island of Crete, Greece, in much of the rest of Greece population and in southern Italy compared to USA population, led Keys to hypothesize that the diet of those populations, characterized by a low content of animal fats, represented a protection factor, and to initiate the long-term observational study known as the Seven Countries Study, an epidemiological longitudinal study and the best known study on the Mediterranean diet.
This study showed:

  • an inverse correlation between diet and the risk of death in general and from cardiovascular diseases;
  • that saturated fats was the major dietary risk factor;
  • that a Mediterranean-type diet led to a reduction in the risk of developing cardiovascular diseases.

Characteristics of the mediterranean diet

Mediterranean diet is a dietary pattern characterized by the consumption of large quantities of vegetables, legumes, fruits, cereals, preferably whole grain, and extra virgin olive oil, which ensures a good supply of fiber, antioxidants, phytosterols, polyphenols and unsaturated fatty acids.
Regarding products of animal origin, the consumption of meat, especially red meat and red meat products, as well as high-fat dairy products should be limited, whereas fish and seafood should be present.
Ethanol consumption should be moderate, primarily in the form of red wine and during meals.
And in the Greek population segment that participated to EPIC study, extra virgin olive oil, vegetables, legumes, a moderate intake of ethanol, together with a low consumption of meat and meat products are the dominant components predictor of lower mortality.
Cornerstone of the mediterranean diet is extra virgin olive oil. It is an excellent source of monounsaturated fatty acids and contains over 2000 different compounds, many with antioxidant activity.
Extra virgin olive oil: the cornerstone of the mediterranean dietBeing the major source of lipids, when associated with a low consumption of high fat animal products, it ensures a high ratio of monounsaturated to saturated fatty acids, which improves lipid profile and glycemic control in diabetics.
However, it is misleading to focus on a single element of this eating pattern; it does not exist “the magic bullet” as shown by studies focused on a single element. People don’t eat a single nutrient but a complex of them and, more important, nutrients interact with each other in synergistic or antagonist ways. So, the health benefits of Mediterranean diet are due to all its components.

Mediterranean diet and chronic diseases

After the Seven Countries Study, many studies have shown the effectiveness of this dietary pattern in primary and secondary prevention of the main chronic diseases, from cardiovascular diseases to depressive disorders, as well as a reduction in mortality in general.
Here are some examples.

  • A meta-analysis have evaluated the association between adherence to the mediterranean diet pattern, mortality, and incidence of diseases, showing that “greater adherence to a Mediterranean Diet is significantly associated with a reduced risk of overall mortality, cardiovascular mortality, cancer incidence and mortality, and incidence of Parkinson’s disease.” (Sofi F. at al. BMJ 2008, see References).
  • A randomized multicenter study has demonstrated the its efficacy in primary prevention of cardiovascular events in subjects at high cardiovascular risk.
  • It is related to a lower risk for Alzheimer’s disease and to its subsequent course and outcome: the higher adherence is associated with lower mortality and it is suggested a dose-response effect.
  • Mounting evidence suggest a protective effect on weight gain.
  • It has been reported an inverse association between adherence to this dietary pattern and the incidence of type 2 diabetes among initially healthy people and in patients who survived myocardial infarction.
  • It is associated with a lower prevalence of the metabolic syndrome.
  • Epidemiological and interventional studies have revealed a protective effect against mild chronic inflammation and its metabolic complications.
  • There is evidence that adherence to the Mediterranean diet may have a protective role in the prevention of depressive disorders.

Role in the reduction of greenhouse gas emissions

The mediterranean diet is able to improve public health also by contributing to the reduction of greenhouse gas emissions, namely, carbon dioxide or CO2, methane, nitrous oxide and similar, from the livestock sector, responsible for 4/5 of emissions related to agriculture. These emissions are greater than those due to transport, and second only to those of energy production. Adding to this that world population is growing, and that this growth is accompanied by an increase in per capita consumption of meat, with estimates that by 2030 there will be an increase in meat production of 85% compared to 2000, the role of the mediterranean diet in reducing greenhouse gas emissions is even more evident.
Analyzing in detail the greenhouse gas emission from cattle farming, the major contributor of the emissions in the livestock sector:

  • about 40% comes from the loss of annual plants, grasses and trees that covered the land where the crop is grown;
  • 32% from the methane emissions of animal waste, and by the animals themselves as a result of digestion;
  • 14% from fertilizers to grow feed grain, 16 pounds of grain fodder for every kilogram of meat consumed;
  • 14% from agricultural production generally.

Production of different foods and carbon dioxide emissionThe figure below compares CO2 emission from the production of different foods, considering portions of 225 g, with those from a gasoline car that travels about 12 km per litre of fuel.
So producing 225 grams of beef releases to the atmosphere an amount of greenhouse gases almost 13 times greater than that released producing an equal amount of chicken, and even 57 times greater if we consider potatoes.
To take another example, to produce 41 kilograms of beef, the amount annually consumed by the average American, it releases the same amount of CO2 of a car traveling about 3,000 km.

References

Di Daniele N., Noce A., Vidiri M., Moriconi E., Marrone G., Annicchiarico-Petruzzelli M., D’Urso G., Tesauro M., Rovella V., De Lorenzo A. Impact of Mediterranean diet on metabolic syndrome, cancer and longevity. Oncotarget 2017;8:8947-8979. doi:10.18632/oncotarget

Estruch R., Ros E., Salas-Salvadó J., et al. Primary prevention of cardiovascular disease with a Mediterranean Diet. N Engl J Med 2013;368:1279-1290. doi:10.1056/NEJMoa1200303

Friel S., Dangour A.D., Garnett T., Lock K., Chalabi Z., Roberts I., Butler A., Butler C.D., Waage J., McMichael A.J. and Haines A. Public health benefits of strategies to reduce greenhouse-gas emissions: food and agriculture. Lancet 2009;374:2016-2025. doi:10.1016/S0140-6736(09)61753-0

Giugliano D. and Esposito K. Mediterranean Diet and Cardiovascular Health. Annals NY Acad Sci 2005;1056(1):253-260. doi:10.1196/annals.1352.012

Giugliano D. and Esposito K. Mediterranean diet and metabolic diseases. Curr Opin Lipidol 2008;19:63-68. doi:10.1097/MOL.0b013e3282f2fa4d

Keys A. Mediterranean diet and public health: personal reflections. Am J Clin Nutr 1995;61:1321S-1323S doi:10.1093/ajcn/61.6.1321S

Keys A., Aravanis C., Blackburn H., Buzina R., Djordjevic B.S., Dontas A.S., Fidanza F., Karvonen M.J., Kimura N., Menotti A., Mohacek I., Nedeljkovic S., Puddu V., Punsar S., Taylor H.L., Van Buchem F.S.P. Seven Countries: A Multivariate Analysis of Death and Coronary Heart Disease. Harvard University Press, Cambridge, Harvard University Press, ISBN: 0-674-80237-3, 1980. 381 pp.

Martínez-González M.Á., de la Fuente-Arrillaga C., Nunez-Cordoba J.M., Basterra-Gortari F.J., Beunza J.J., Vazquez Z., Benito S., Tortosa A., Bes-Rastrollo M. Adherence to Mediterranean diet and risk of developing diabetes: prospective cohort study. BMJ 2008;336:1348-1351. doi:10.11bmj.39561.501007.BE

Martín-Peláez S., Fito M., Castaner O. Mediterranean diet effects on type 2 diabetes prevention, disease progression, and related mechanisms. A review. Nutrients 2020;12(8):2236. doi:10.3390/nu12082236

Mentella M.C., Scaldaferri F., Ricci C., Gasbarrini A., Miggiano G.A.D. Cancer and Mediterranean Diet: a review. Nutrients 2019; 11(9):2059. doi:10.3390/nu11092059

Nestle M. Mediterranean diets: historical and research overview. Am J Clin Nutr 1995;61:1313S-1320S doi:10.1093/ajcn/61.6.1313S

Samieri C., Okereke O.I., E. Devore E.E. and Grodstein F. Long-term adherence to the Mediterranean Diet is associated with overall cognitive status, but not cognitive decline, in women. J Nutr 2013;143:493-499. doi:10.3945/jn.112.169896

Sánchez-Villegas A., Delgado-Rodríguez M., Alonso A., Schlatter J., Lahortiga F., Serra Majem L., Martínez-González M.A. Association of the Mediterranean Dietary pattern with the incidence of depression: The Seguimiento Universidad de Navarra/University of Navarra Follow-up (SUN) Cohort. Arch Gen Psychiatry. 2009;66:1090-1098 doi:10.1001/archgenpsychiatry.2009.129

Scarmeas N., Luchsinger J.A., Mayeux R. and Stern Y. Mediterranean diet and Alzheimer disease mortality. Neurology 2007;69(11):1084-1093 doi:10.1212/01.wnl.0000277320.50685.7c

Schröder H. Protective mechanisms of the Mediterranean diet in obesity and type 2 diabetes. J Nutr Biochem 2007;18:149-160. doi:10.1016/j.jnutbio.2006.05.006

Seattle Food System Enhancement Project. Greenhouse Gas Emission Study. 2012

Sofi F., Cesari F., Abbate R., Gensini G.F. and Casini A. Adherence to Mediterranean diet and health status: meta-analysis. BMJ 2008;337:a1344. doi:10.1136/bmj.a1344

Subak S. Global environmental costs of beef production. Ecol. Econom. 1999;30:79-91. doi:10.1016/S0921-8009(98)00100-1

Trichopoulou A., Bamia C. and Trichopoulos D. Anatomy of health effects of Mediterranean diet: Greek EPIC prospective cohort study. BMJ 2009;338:b2337. doi:10.1136/bmj.b2337

Trichopoulou A., Costacou T., Bamia C., Trichopoulos D. Adherence to a Mediterranean Diet and Survival in a Greek Population. N Engl J Med 2003;348:2599-2608. doi:10.1056/NEJMoa025039

VanItallie T.B. Ancel Keys: a tribute. Nutr Metab (Lond) 2005;2:4. doi:10.1186/1743-7075-2-4

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