Determinants of the omega-3 index in a Mediterranean population at increased risk for CHD

The omega-3 index, defined as the sum of EPA and DHA in erythrocyte membranes expressed as a percentage of total fatty acids, has been proposed as both a risk marker and risk factor for CHD death. A major determinant of the omega-3 index is EPA + DHA intake, but the impact of other dietary fatty acids has not been investigated. In a cross-sectional study on 198 subjects (102 men and 96 women, mean age 66 years) at high cardiovascular risk living in Spain, the country with low rates of cardiac death despite a high prevalence of cardiovascular risk factors, dietary data were acquired from FFQ and blood cell membrane fatty acid composition was measured by GC. The average consumption of EPA + DHA was 0.9 g/d and the mean omega-3 index was 7.1%. In multivariate models, EPA + DHA intake was the main predictor of the omega-3 index but explained only 12% of its variability (P<0.001). No associations with other dietary fatty acids were observed, Although the single most influential determinant of the omega-3 index measured here was the intake of EPA + DHA, it explained little of the former's variability; hence, the effects of other factors (genetic, dietary and lifestyle) remain to be determined. Nevertheless, the high omega-3 index could at least partially explain the paradox of low rates of fatal CHD in Spain despite a high background prevalence of cardiovascular risk factors.