Plasma n-6 and n-3 polyunsaturated fatty acids as biomarkers of their dietary intakes: a cross-sectional study within a cohort of middle-aged French men and women

Objective: To measure the correlations between habitual intakes of individual n-6 and n-3 polyunsaturated fatty acids (PUFA) and their percentages in total plasma fatty acids in a population of adult men and women. Subjects/Methods: Two hundred and seventy-six men and 257 women aged 45-60 (men) or 35-60 (women) at baseline, volunteers of the French SU.VI.MAX cohort. Fifteen 24-h record questionnaires were used to estimate the habitual intake of energy, total fat and linoleic, alpha-linolenic acid, arachidonic, eicosapentaenoic (EPA), n-3 docosapentaenoic (DPA) and docosahexaenoic (DHA) acids. Fatty acid composition of fasting plasma total lipids has been determined at baseline. Results: Dietary intakes of linoleic acid, arachidonic acid, EPA and DHA were weakly but significantly correlated (0.16<r<0.28, P<0.01) with their respective percentages in plasma total fatty acids in both men and women. No correlation was observed between the plasma levels of alpha-linolenic acid and its dietary intake, and between the plasma levels of arachidonic acid and long-chain n-3 PUFA and the intakes of their 18-carbon precursors, linoleic and alpha-linolenic acid, respectively. Conclusions: The percentages of linoleic acid, arachidonic acid, EPA and DHA in plasma total fatty acids, but not that of alpha-linolenic acid, are acceptable markers of their habitual levels of intake. The plasma levels of long-chain n-6 and n-3 PUFA are not influenced by the intake levels of their precursors, linoleic and alpha-linolenic acids.