Circulating plasma phospholipid fatty acid levels as a biomarker of habitual dietary fat intake: The INTERMAP/INTERLIPID Study: Circulating fatty acid level and intake

Background: Accurate assessment of fat intake is essential to examine relationships between diet and disease risk. However, estimating individual intakes of fat quantity by dietary assessment is difficult. Objective: We assessed the association of plasma phospholipid fatty acid levels with dietary intake of fatty acids in the INTERMAP/INTERLIPID study, conducted with a standardized protocol. Methods: The study participants were 1339 men and women ages 40–59 years from five Japanese populations one from Hawaii; four from Japan. Fatty acid intake was estimated from four standardized 24-hour dietary recalls. Plasma phospholipid fatty acid composition was analyzed by gas chromatography. We illustrated the relationship between intake and circulating fatty acid levels using Spearman's rank-correlation coefficients, mean, and median values. Results: Spearman's rank-correlation coefficients between intake (g/d) and circulating fatty acid levels (µg/ml) were -0.03 to 0.21 for saturated fatty acids and monounsaturated fatty acids and -0.04 to 0.32 for trans fatty acids. The coefficients for essential n-3 and n-6 fatty acids were moderate to high, especially for eicosapentaenoic acid (EPA), 0.60; docosahexaenoic acid (DHA), 0.41; and EPA+DHA, 0.51. The circulating levels and intake of marine-derived n-3 fatty acids showed a linear association, at least for the intake of EPA+DHA up to 2.1 g/d. Conclusion: We observed high correlation between intake and circulating levels of marine-derived n-3 fatty acids in participants from Japanese and Japanese-American populations with high and low fish intake. Plasma phospholipid marine-derived n-3 fatty acid measurements are a simple and reliable biomarker for assessing dietary intake.