Plasma fatty acid composition as an indicator of habitual dietary fat intake in middle-aged adults. The Atherosclerosis Risk in Communities (ARIC) Study Investigators.

We compared the plasma fatty acid (FA) composition of the habitual diet, measured by a 66-item semiquantitative food-frequency questionnaire (FFQ), with the corresponding plasma phospholipid and cholesterol ester (CE) FA composition measured by gas chromatography in 3570 free-living, middle-aged adults. Pearson correlations between dietary and plasma FA (expressed as % of total FAs) for phospholipid and CE, respectively, were as follows: saturated FA (r = 0.15 and 0.23), monounsaturated FA (r = 0.05 and 0.01), polyunsaturated FA (r = 0.25, 0.31), linoleic acid (r = 0.22 and 0.28), linolenic acid (r = 0.15 and 0.21), eicosapentaenoic acid (r = 0.20 and 0.23), and docosahexaenoic acid (r = 0.42 and 0.42). The correlations between diet and plasma FAs held relatively constant regardless of whether participants were overweight, had chronic diseases, were alcohol drinkers, or were cigarette smokers. However, at similar reported dietary intakes, the plasma lipid concentration of saturated FAs was higher and/or that of linoleic acid was lower in people with these characteristics compared with those without these characteristics.