Higher adherence to the Mediterranean diet is consistently associated with lower mortality, less heart disease and less cancer. The evidence for cardiovascular disease is the strongest and is likely causal; for longevity in itself the evidence remains observational.
Large observational studies show that people who closely follow the Mediterranean diet die prematurely less often. In a Greek cohort of more than 22,000 adults, every two-point increase on a 10-point diet-adherence scale was associated with a 25% lower risk of death (adjusted hazard ratio 0.75). The same cohort also showed lower mortality from heart disease (hazard ratio 0.67) and cancer (hazard ratio 0.76). These are strong associations, but the research is observational: a direct causal link has not been established. Factors such as lifestyle, income and overall health can influence the results (PMID 12826634).
The evidence is strongest for cardiovascular disease and related risk factors such as high blood pressure, abnormal blood lipids and excess weight. Both observational studies and intervention studies point in the same direction: the Mediterranean diet reduces the risk of cardiovascular disease. This makes a causal relationship more plausible here than for other outcomes (PMID 34423871, 34204683).
For type 2 diabetes the evidence exists but is somewhat less consistent. The diet is associated with a lower likelihood of developing diabetes and with better blood sugar control in people who already have the condition. For cognitive decline and Alzheimer's disease there are indications that the diet has a beneficial effect, but the evidence is mainly observational and not yet strong enough to claim a causal relationship (PMID 34423871, 34204683, 37432307).
When the Mediterranean diet is combined with other healthy habits such as sufficient physical activity and not smoking, large cohort studies estimate that disease-free life expectancy can increase by 8 to 10 years. In these estimates, the individual contribution of the diet has not been separated from the other lifestyle factors, so this figure cannot be attributed to the diet alone (PMID 37867396).
The Mediterranean diet also changes the composition of gut bacteria in a way that appears to be beneficial for inflammatory processes and metabolism. Whether this is the primary explanation for the health benefits has not yet been sufficiently studied (PMID 37432307). Evidence that the diet also influences biological ageing processes at the cellular level remains limited and comes largely from animal or laboratory research (PMID 39275194).
An important caveat concerns the so-called 'Blue Zones', regions with many very elderly people such as Sardinia and Ikaria. Although the Mediterranean diet is often cited there as an explanation, researchers warn that the dietary patterns in these zones are not homogeneous and change over time. Social cohesion, physical activity and genetics likely also play a role. The evidence that the diet alone is responsible for the exceptionally high ages reached in those regions is insufficient (PMID 35780634).
The claims are based on one large prospective cohort (PMID 12826634), multiple reviews and meta-analyses (PMID 34423871, 34204683, 37432307, 37506751, 39275194), a lifestyle cohort (PMID 37867396) and a critical analysis of Blue Zones (PMID 35780634). The cohort study includes 22,043 participants; the remaining studies did not specify explicit participant numbers in the supplied claims. The total estimated number of participants across all studies is unknown but well above 22,000.