Incorporation of eicosapentaenoic and docosahexaenoic acids into lipid pools when given as supplements providing doses equivalent to typical intakes of oily fish

Abstract

Background: Estimation of the intake of oily fish at a population level is difficult. The measurement of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in biological samples may provide a useful biomarker of intake.

Objective: We identified the most appropriate biomarkers for the assessment of habitual oily fish intake and changes in intake by elucidating the dose- and time-dependent response of EPA and DHA incorporation into various biological samples that represent roles in fatty acid transport, function, and storage.

Design: This was a double-blind, randomized, controlled intervention trial in 204 men and women that lasted 12 mo. EPA and DHA capsules were provided in a manner to reflect sporadic consumption of oily fish (ie, 1, 2, or 4 times/wk). EPA and DHA were assessed at 9 time points over 12 mo in 9 sample types (red blood cells, mononuclear cells, platelets, buccal cells, adipose tissue, plasma phosphatidylcholine, triglycerides, cholesteryl esters, and nonesterified fatty acids).

Results: A dose response (P < 0.05) was observed for EPA and DHA in all pools except for red blood cell EPA (P = 0.057). EPA and DHA measures in plasma phosphatidylcholine and platelets were best for the discrimination between different intakes (P < 0.0001). The rate of incorporation varied between sample types, with the time to maximal incorporation ranging from days (plasma phosphatidylcholine) to months (mononuclear cells) to >12 mo (adipose tissue).

Conclusions: Plasma phosphatidylcholine EPA plus DHA was identified as the most suitable biomarker of acute changes in EPA and DHA intake, and platelet and mononuclear cell EPA plus DHA were the most suitable biomarkers of habitual intake.

FIGURE 1.

Flow of participant involvement in the study. Randomization group 2C (shaded in gray) is not considered further in this article. The 2C-portions group received the equivalent amount of EPA plus DHA that was provided in the 2-portions group but which was distributed evenly over the 7 d.

FIGURE 2.

Comparison of mean (±SD) EPA plus DHA amounts (percentage of total fatty acids) between the 9 sample types at 12 mo for the groups who received EPA plus DHA equivalent to 0, 1, 2, and 4 portions of oily fish per week. The dose response in the pools was compared by using a multivariate regression model in which each pool was a component of the outcome, and linearity with dose was assumed. Regression coefficients (slopes) and associated P values for the effect of dose in each pool are shown, and pairwise comparisons between the slopes were made. ⁺Significant difference between adipose tissue and other pools, P < 0.001; *significant difference between plasma phosphatidylcholine and other pools, P < 0.001; ^#significant difference between platelets and other pools, P < 0.001; ^£significant difference between nonesterified fatty acids and other pools, P < 0.001.

FIGURE 3.

Mean (±SE) changes from baseline of EPA and DHA concentration (percentage of total fatty acids) in plasma PC, PLAT, and MNC in response to EPA and DHA equivalent to 0, 1, 2, and 4 portions of oily fish per week for 12 mo. The control group is represented by diamonds, the 1-portion group is represented by Xs, the 2-portions group is represented by open circles, and the 4-portions group is represented by closed circles. The panels provide graphical representation of EPA and DHA responses to doses over the 12-mo intervention. Statistical analyses of responses are shown in Tables 2–4. MNC, mononuclear cells; PC, plasma phosphatidylcholine; PLAT, platelets.