A great amount of evidence from epidemiological studies and clinical trials supports a protective effect against coronary heart disease for fish consumption and intake of marine omega-3 fatty acids. Biological pathways for this risk reduction include membrane stabilization in the cardiac myocite, inhibition of platelet aggregation, favourable modifications of the lipid profile, decrease in blood pressure and reduction of the inflammatory response of the endothelium. Results from epidemiological studies suggest a threshold effect for the consumption of fish and omega-3 fatty acids. Risk reduction is especially important for cardiac sudden death. Nevertheless, protection against non-fatal coronary heart disease has also been observed. Recently published studies have shown that mercury intake, present in high concentrations in fish, could counteract the beneficial effect from fish consumption.