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.