Inter-individual variability in the incorporation of marine omega-3 fatty acids (FA) into blood differs significantly between subjects. While marine oils typically contain distinct combinations of eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA), and docosahexaenoic acid (DHA), it remains unknown whether this inter-individual variability is uniform or differs according to the specific FA type and blood lipid pools. Retrospective analyses were undertaken using data from two randomized, double-blind, crossover human trials. In Study 1, ten healthy female participants consumed 9 g of either pure EPA or pure DPA over 7 days1. In Study 2, twelve healthy female participants consumed 6 g of pure EPA, DPA, or DHA over 6 days2. Olive oil served as the placebo in both studies. Plasma phospholipid (PL), plasma triacylglycerol (TAG), plasma cholesteryl ester (CE), and red blood cell (RBC) FA compositions were determined at baseline, day 3, and day 6 (Study 1), or baseline, day 4, and day 7 (Study 2). Responses were quantified using incremental area under the curve (iAUC). Consistency of individual responses across treatments was assessed using intraclass correlation coefficients (ICC). There was considerable inter-individual variability in the incorporation of EPA, DPA, and DHA across all blood lipid pools. EPA exhibited the greatest and most significant absolute increases in plasma PL, plasma CE, and RBC fractions across both studies, whereas DPA and DHA responses were smaller and highly variable. Calculated ICC values comparing individual responses across different FA treatments were exceptionally low, with the majority falling below 0.20 or displaying negative values (ranging from -0.536 to +0.220). This lack of correlation reveals that an individual's capacity to incorporate one specific omega-3 FA does not predict their capacity to incorporate another. The singular exception occurred within the plasma TAG compartment, which demonstrated weak-to-moderate cross-treatment consistency for EPA vs. DPA in both trials (Study 1: ICC = 0.295; Study 2: ICC = 0.442). Conversely, structural and functional membrane pools exhibited the most profound cross-treatment volatility (e.g., Study 2 plasma PL DPA vs. DHA: ICC = -0.536). The uptake of marine omega-3 FAs does not follow a uniform intra-individual pattern. While initial, non-specific transport via plasma TAG maintains slight cross-FA consistency, downstream assimilation into structural lipid pools (plasma PL and RBC) is governed by independent, highly selective metabolic pathways unique to each specific FA and individual. These findings confirm that a uniform approach to marine oil supplementation overlooks substantial individual metabolic differences. Instead, effective therapy requires personalised omega-3 strategies tailored to each individual's metabolic profile.
1Miller E, et al, A short-term n-3 DPA supplementation study in humans. Eur J Nutr. 2013;52:895-904.
2Guo XF, et al, Different metabolism of EPA, DPA and DHA in humans: A double-blind cross-over study. PLEFA. 2020;158:102033.