Several studies demonstrated the beneficial and preventive role of Mediterranean diet in the occurrence of cardiovascular diseases, chronic neurodegenerative diseases and neoplasms, obesity and diabetes.

In randomized intervention trials, Mediterranean diet improved endothelial function and significantly reduced waist circumference, plasma glucose, serum insulin and homeostasis model assessment score in metabolic syndrome.

Several studies support favorable effects of Mediterranean diet on plasma lipid profile: reduction of total and plasma LDL cholesterol levels, plasma triglyceride levels, and apo-B and VLDL concentrations, and an increase in plasma HDL cholesterol levels. This effect is associated with increased plasma antioxidant capacity, improved endothelial function, reduced insulin resistance, and reduced incidence of the metabolic syndrome. The beneficial impact of fish consumption on the risk of cardiovascular diseases is the result of synergistic effects of nutrients in fish.

Fish is considered an excellent source of protein with low saturated fat, nutritious trace elements, long-chain omega-3 polyunsaturated fatty acids (LCn3PUFAs), and vitamins D and B.

Fish consumption may be inversely associated with ischemic stroke but not with hemorrhagic stroke because of the potential antiplatelet aggregation property of LCn3PUFAs. Total stroke risk reduction was statistically significant for fish intake once per week, while the risk of stroke was lowered by 31% in individuals who ate fish 5 times or more per week. In the elderly, moderate consumption of tuna/other fish, but not fried fish, was associated with lower prevalence of subclinical infarcts and white matter abnormalities on MRI examination.

Dietary intake of omega-3 fatty acids in a moderate-to-high range does not appear to be associated with reduced plaque, but is negatively associated with carotid artery intima-media thickness.

Greater adherence to Mediterranean diet is associated with significant reduction in overall mortality, mortality from cardiovascular diseases and stroke, incidence of or mortality from cancer, and incidence of Parkinson's disease and Alzheimer's disease and mild cognitive impairment.