The Mediterranean Diet: Myth or Scientific Reality?

The “Mediterranean diet” is promoted globally as a symbol of health, associated with the prevention of cardiovascular disease, cancer, and longevity. There is, however, a fundamental problem: the Mediterranean diet is practically vaguely defined, with over 22 contradictory variants in the scientific literature. What Italian grandmothers ate in the 1960s and what “Mediterranean diet” means today in studies are two completely different things.

What Is the Mediterranean Diet, Really?

The gastronomy of Mediterranean countries has nothing to do with any standardized Mediterranean diet — the latter being a generic platitude conveniently served in place of individualized professional nutrition. The “Mediterranean diet” is practically a blank canvas on which every researcher embroiders what they see fit, adapted to the interests of their study.

The difference between authentic Mediterranean traditions and the many diets called “Mediterranean” is sacrificed on the altar of this symbol — much like in The Emperor’s New Clothes, in which Andersen presents the story of a king convinced to walk around naked by a smooth-talking tailor. Just like those clothes, the wildly popular Mediterranean diet, as a standardized entity, does not exist.

Where the Myth of the Mediterranean Diet Comes From

The first observational study of the “Mediterranean diet” conducted on elderly people living in three Greek villages questioned only eight types of food: vegetables, legumes, fruits, nuts, cereals, meat, dairy, and alcohol (Trichopoulou A. et al., 1995). Even fish only appeared on the table ten years later (Trichopoulou A. C., 2005).

The main problem with observational studies is that they can be so easily influenced by biases that anything one wishes to prove or disprove can be achieved with statistics and semantics. Only a few observational studies are adjusted for imprecise measurements or potential confounding factors. And the many working definitions used subjectively by different authors contradict each other on the same topic.

A Concrete Example: The ORDET Study and the Italian Mediterranean Diet

An illustrative example is the recently published Italian ORDET cohort study, which concludes that “a typical Italian Mediterranean diet protects against the development of breast cancer, especially in postmenopausal women, possibly through the modulation of chronic inflammation” (Quartiroli, 2024). The study compares self-reported compliance with the Italian Mediterranean Index, based on an adapted version of the Greek Mediterranean Diet score, the Greek Mediterranean Index, and the DASH and EAT-Lancet scores.

The concrete result, reading the entire article and not just the abstract: no other “Mediterranean” diet besides the Italian one was associated with a reduced risk of breast cancer. Not even the Greek one. And the Italian Mediterranean Index proved protective only in postmenopausal women — and statistically significant only in 29 out of the 9,144 participants.

How the ORDET Study Evolved Over Time

• Initially, there were no nutritional data or measured inflammation markers — this was not a nutrition study. The original cohort consisted of 10,786 healthy women, recruited between 1987 and 1992 in the Province of Varese, Italy.
• The first change came two and a half years after the start, when diet entered the equation: the remaining 9,144 women completed a semi-quantitative food frequency questionnaire, self-reporting their habits from the previous year.
• The second change came twenty-two and a half years later, when measurements of inflammatory markers were “patched in” in 2017 — not evaluated within the ORDET study itself, but copied from two other case-control studies, obtained with different kits and standardized statistically afterward.

What is the clinical relevance of the non-specific inflammatory marker CRP, tailor-patched from other studies’ data, which even so was statistically significant in only 29 out of 9,144 participants? Can eminence make 29 greater than 9,144?

Over 22 Definitions of the Same “Mediterranean Diet”

Mixing case-control data with cohort data has become a normalized behavior, even though these types of data are fundamentally different. Most studies supporting “Mediterranean diets” are retrospective case-control studies, which cannot establish causality and which are scientifically designed for rare diseases — not cancer or cardiovascular disease.

Among the many “Mediterranean diets” invented over the years:

• The Mediterranean Diet Score (Panagiotakos, Pitsavos, and Stefanadis, 2006)
• The Mediterranean Diet Scale (Willett, 1995)
• The Mediterranean Dietary Pattern (Martínez-González M. A., 2002)
• The Mediterranean-Style Dietary Pattern Score (Rumawas, 2009)
• The Mediterranean Dietary Pattern Adherence Index (Sanchez-Villegas, 2006)
• The Relative Mediterranean Diet (Buckland et al., 2009)
• The Mediterranean Adequacy Index (Alberti, 2009)

There are at least 22 definitions of the “Mediterranean” diet (Hernandez Ruiz, 2015). No Italian grandmother was asked in the 1960s whether she agreed with Ancel Keys’ idea of replacing butter with margarine, or whether Grana Padano is a non-Mediterranean food.

Why Study Quality Matters in Nutrition

Availability bias is a mental shortcut by which decisions are based on popular rather than scientifically precise information. Case-control studies are cheaper and easier to conduct, hence more prevalent — and, although more prone to selection bias and recall bias, their greater availability gives them an unjustified weight in shaping general opinion.

The lack of standardized guidelines is a recognized limitation of PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses), while study design, sampling, follow-up, and confounding factors are frequently overlooked (Chrystoja, 2021). As a result, 60% of available systematic analyses do not apply adequate statistics and do not meet methodological quality standards (Huedo-Medina, 2016).

Conclusion: The Mediterranean Diet as a Clinical Nutrition Tool

In practice, there is no single “Mediterranean diet,” but over twenty subjectively defined variants. These variants are not nutritional interventions, but questionnaires designed to summarize self-reported compliance with a calculated index — with limited utility in individualized clinical practice.

Some researchers consider them useful in evaluating dietary trends for public health guidelines. But these guidelines remain globally ignored, including by those who publish them, and are devoid of concrete clinical utility. If you are an oncological, cardiovascular, or metabolic-risk patient and want to know what you should eat, the answer is not found in a vague symbol, but in an individualized nutritional assessment.

References

Alberti, A. D. (2009). “The Mediterranean Adequacy Index: further confirming results of validity.” Nutrition, Metabolism and Cardiovascular Diseases.

Bach, A. et al. (2006). “The use of indexes evaluating the adherence to the Mediterranean diet in epidemiological studies: a review.” Public Health Nutrition.

Buckland, G. et al. (2009). “Adherence to the Mediterranean diet and risk of coronary heart disease in the Spanish EPIC Cohort Study.” American Journal of Epidemiology.

Chrystoja, B. R. (2021). “A systematic comparison of the global comparative risk assessments for alcohol.” Addiction.

Hernandez Ruiz, A. et al. (2015). “Description of indexes based on the adherence to the Mediterranean dietary pattern: a review.” Nutrición Hospitalaria (SENPE).

Huedo-Medina, T. B. (2016). “Methodologic quality of meta-analyses and systematic reviews on the Mediterranean diet and cardiovascular disease outcomes: a review.” The American Journal of Clinical Nutrition.

Martínez-González, M. A. (2002). “Mediterranean diet and reduction in the risk of a first acute myocardial infarction: an operational healthy dietary score.” European Journal of Nutrition.

Panagiotakos, D. B., Pitsavos, C., and Stefanadis, C. (2006). “Dietary patterns: a Mediterranean diet score and its relation to clinical and biological markers of cardiovascular disease risk.” Nutrition, Metabolism and Cardiovascular Diseases.

Quartiroli, M. et al. (2024). “Adherence to Diet Quality Indices and Breast Cancer Risk in the Italian ORDET Cohort.” Nutrients.

Rumawas, M. E. (2009). “The development of the Mediterranean-style dietary pattern score and its application to the American diet in the Framingham Offspring Cohort.” The Journal of Nutrition.

Sanchez-Villegas, A. et al. (2006). “Adherence to a Mediterranean dietary pattern and weight gain in a follow-up study: the SUN cohort.” International Journal of Obesity.

Trichopoulou, A. C. (2005). “Mediterranean diet and survival among patients with coronary heart disease in Greece.” Archives of Internal Medicine.

Trichopoulou, A. et al. (1995). “Diet and overall survival in elderly people.” BMJ.

van Enst, W. A. (2014). “Investigation of publication bias in meta-analyses of diagnostic test accuracy: a meta-epidemiological study.” BMC Medical Research Methodology.

Willett, W. C. (1995). “Mediterranean diet pyramid: a cultural model for healthy eating.” The American Journal of Clinical Nutrition.