The relationship of fish and dietary omega-3 fatty acids and cardiovascular disease (CVD) has been investigated in numerous studies and comprehensive reviews and recommendations exist, but guidance on blood concentrations is missing. Some prospective fish oil treatment investigations report a significant reduction in CVD events but others do not.

A recent meta-analysis did not find a statistically significant relationship between omega-3 consumption and CVD mortality, but it failed to take into account the implications of variability in individual blood levels of omega-3 fatty acids.

Blood levels of omega-3 fatty acids can be influenced by dietary intake of omega-3 fatty acids and intake with oral supplements. The Multiple Risk Factor Intervention Trial reported in 1995 that serum omega-3 fatty acids blood levels were inversely correlated with coronary heart disease (CHD).9 An association of dietary sources of nonfried fish and blood levels of eicosapentaenoic acid (EPA) + docosahexaenoic acid (DHA) were reported in the Atherosclerosis Risk In Communities (ARIC) investigation and the Multi-Ethnic Study of Atherosclerosis (MESA) investigations.

Blood levels of dietary omega-3 fatty acids can vary based on geography and diet habits. For example, Japanese living in Japan have higher blood omega-3 fatty acid levels than whites living in Pennsylvania and Japanese Americans living in Honolulu. The lower 5th percentile of blood omega-3 fatty acids in the Japanese living in Japan is higher than the mean levels in whites and Japanese Americans even though total fat is comparable.