The ARIC clinical history did collect some dietary history using the Willett Questionnaire, and asked a few questions regarding fish consumption. However, specific questions were brief and only semi-quantitative. Direct measurement of plasma fatty acid content as an ancillary study in the Minnesota cohort of the ARIC study gave far more objective information on specific fatty acid consumption and was invaluable in sorting out the true role that various fatty acids play in the prevention of coronary heart disease. Furthermore, measurement of plasma fatty acids in Minnesota ARIC subjects allowed investigation of the relationships between plasma fatty acids composition and the vast amount of laboratory and clinical outcome data which the ARIC study collected. Because the clinical and other laboratory data for each ARIC participant were already available in the computerized data base, a tremendous amount of valuable information was derived on plasma fatty acid relationships with laboratory findings and clinical outcome in a large, randomly selected United States population.