Which diet is best supported by evidence for a long, healthy life?

Of all the dietary patterns studied, the Mediterranean diet has the strongest evidence base for a long and healthy life. Multiple large prospective studies and intervention trials show a consistent association with lower rates of cardiovascular disease, reduced mortality and longer lifespan^1,2. It is also linked to a lower risk of type 2 diabetes, less overweight and lower blood pressure. The evidence is largely observational, so other lifestyle factors play a role. But the consistency across so many large studies is impressive.

For the brain, there are also positive signals. Multiple studies in humans suggest that the Mediterranean diet is associated with less cognitive decline in older age and a lower risk of Alzheimer's disease^3,4. This evidence is less extensive than that for cardiovascular disease, but it is certainly there.

The so-called Blue Zones, such as Sardinia and the Greek island of Ikaria, show that long-lived populations traditionally eat a largely plant-based diet in moderate amounts. But researchers caution: the fact that a dietary pattern is found in a long-lived population does not prove that it is the cause of that longevity. The eating patterns in these zones are also not uniform and change over time.

Intermittent fasting, also known as time-restricted eating, shows promising effects on weight and disease prevention in mouse studies and smaller human studies, and also appears to have a positive influence on gut health^5,6. However, large, long-term studies in humans are still lacking. Caloric restriction, eating less without malnutrition, is identified in molecular and animal research as one of the most powerful strategies for slowing biological ageing processes. Direct evidence in healthy humans over the long term is not yet available.

Popular high-protein diets deserve a note of caution. Animal protein has been linked in multiple observational studies to a higher risk of kidney damage and protein loss through urine⁷. Plant-based protein appears to place a lower burden on the kidneys. The evidence is not yet fully conclusive, but the concerns are real enough to take seriously, especially if you already have an elevated risk of kidney disease.