Over half of the U.S. population had an undesirably low omega-3 index based on erythrocyte membrane measurements: results from the cross-sectional National Health and Nutrition Examination survey (NHANES) from August 2021–August 20235

The omega-3 index (O3I; sum of red blood cell (RBC) concentrations of eicosapentaenoic and docosahexaenoic acid) is strongly correlated with risk for sudden cardiac death.We aim to provide nationally representative data on the prevalence of O3I undesirable (8%) categories in the U.S. population ages 6 y and determine associations with selected sociodemographic, lifestyle, intake, and health variables among adults.54% of U.S. persons ages 6 y (n=7213) had an undesirable O3I; the mean O3I was 4.12% and it increased with age.Among adults 20 y (n=5721), the O3I was higher in females, non-Hispanic Asians, persons above the poverty line, those with education beyond high school, non-smokers, polyunsaturated fatty acid supplement users, cholesterol-lowering drug users, and persons with healthy weight or certain heart health conditions.These first data demonstrate that the U.S. population falls short of dietary recommendations to achieve an optimal O3I.