Comparison between plasma and erythrocyte fatty acid content as biomarkers of fatty acid intake in US women

Background: Erythrocyte fatty acids may be superior to plasma fatty acids for reflecting long-term fatty acid intake because of less sensitivity to recent intake and a slower turnover rate. Objective: The objective was to compare the fatty acid content of erythrocytes with that of plasma with respect to their abilities to reflect usual fatty acid intake. Design: Fatty acids in plasma and erythrocytes were measured by capillary gas-liquid chromatography in 306 US women aged 43-69 y. Fatty acid intake was assessed with a food-frequency questionnaire, which was validated for measuring intakes of various fatty acids. Results: Docosahexaenoic acid (DHA, 22:6n-3) in erythrocytes and plasma provided the strongest correlations with its intake, but erythrocyte DHA concentrations [Spearman's partial correlation coefficient (r(s)) = 0.56] were better than plasma DHA concentrations (r(s) = 0.48) as a biomarker. Total trans fatty acids (r(s) = 0.43) and total 18:1 trans isomers (r(s) = 0.42) in erythrocytes were also more strongly correlated with intake than were those in plasma (r(s) = 0.30 and r(s) = 0.29, respectively). Moderate correlations were observed for linoleic acid (18:2n-6; erythrocytes, r(s) = 0.24; plasma, r(s) = 0.25), alpha-linolenic acid (18:3n-3; erythrocytes, r(s) = 0.18; plasma, r(s) = 0.23), and eicosapentaenoic acid (20:5n-3; erythrocytes, r(s) = 0.38; plasma, r(s) = 0.21). For polyunsaturated and trans fatty acids, correlations between intakes and biomarkers improved moderately when average intakes over previous years were used. Conclusion: Erythrocyte n-3 fatty acids of marine origin and trans fatty acid content are suitable biomarkers for long-term intake.