The Mediterranean diet is not a diet in the commercial sense. It is a description of the traditional dietary patterns of populations living in the Mediterranean basin, first studied systematically by Ancel Keys in the Seven Countries Study beginning in 1958. Keys observed that populations in Crete, Greece, and southern Italy had dramatically lower rates of cardiovascular disease than those in Finland and the United States, despite consuming substantial quantities of fat, specifically olive oil. This observation began a research programme that has now generated thousands of studies across multiple continents and decades.
What the Mediterranean Diet Actually Consists Of
- Abundant vegetables, legumes, fruits, and whole grains as the dietary foundation
- Olive oil as the primary fat source, consumed generously
- Fish and seafood several times per week, particularly oily fish high in omega-3 fatty acids
- Moderate amounts of dairy, primarily yoghurt and cheese rather than milk
- Eggs, poultry, and red meat in low to moderate amounts, with red meat consumed rarely
- Wine in moderate amounts, typically with meals, in the traditional pattern
- Herbs and spices rather than salt for flavouring
- Meals eaten slowly and socially, rarely alone
The PREDIMED Trial
The PREDIMED trial, published in the New England Journal of Medicine in 2013 and replicated in PREDIMED-Plus, is the landmark randomised controlled trial of the Mediterranean diet. It followed 7,447 participants at high cardiovascular risk, randomised to a Mediterranean diet supplemented with olive oil, a Mediterranean diet supplemented with nuts, or a low-fat control diet. The trial was stopped early because the benefit of the Mediterranean diet interventions was so clear that continuing the control was considered unethical. Mediterranean diet reduced major cardiovascular events by approximately 30 per cent compared to the low-fat control.
Beyond Cardiovascular Health
The evidence base for Mediterranean diet extends well beyond cardiovascular health. Large cohort studies find consistent associations between Mediterranean diet adherence and reduced incidence of type 2 diabetes, lower rates of depression and cognitive decline, reduced cancer incidence across multiple cancer types, longer telomere length, and lower biological age as measured by epigenetic clocks. A 2023 meta-analysis of 22 systematic reviews covering 13 million people found that Mediterranean diet was the dietary pattern with the strongest and most consistent evidence for mortality reduction across all causes.
Why the Mediterranean Diet Works
The mechanisms through which Mediterranean diet exerts its benefits are multiple and synergistic. High polyphenol intake from olive oil, vegetables, and moderate wine reduces oxidative stress and inflammatory signalling. High omega-3 intake from fish reduces pro-inflammatory eicosanoid production. High fibre intake from legumes, vegetables, and whole grains feeds the gut microbiome, which regulates systemic inflammation. Moderate protein with high plant protein proportion improves metabolic markers. Low ultra-processed food content reduces the advanced glycation end products and industrial seed oils that drive inflammatory damage. No single mechanism explains the benefit; the dietary pattern as a whole produces synergistic effects.