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New study reveals that the lipid structure of EPA and DHA sources does not determine their uptake into the blood lipids of healthy adults

Published on

28 September 2016

By Rob Winwood

There has been considerable debate with regard to the bioavailability of the marine omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). A new study from the University of Southampton (1) in the UK has determined the metabolic fate of EPA and DHA in nine human volunteers when consumed either as the unmodified triglyceride (uTAG), re-esterified (rTAG), ethyl ester (EE), or free fatty acid (FFA) form. This study measured the uptake of blood lipids, both immediately post-prandially and following 12 weeks of supplementation.

NUTRI-FACTS reported on a study in 2015 (2, 3) which did not show any significant difference in EPA and DHA incorporation into plasma and red blood cells after four weeks of supplementation (1.3g/day of ca. 61% EPA:39% DHA) with native fish, krill oil, and ethyl ester (EE) fish oil.

Concentrated, high-dose commercial forms of fish oil often deliver EPA and DHA in either the EE or rTAG form. The new study (1) was conducted with healthy males consuming 1.47 g of marine omega-3 fatty acids (ca. 3:1 EPA:DHA) as part of a daily test meal for 12 weeks. Firstly, the study was able to confirm that the gelatin-based enteric coatings, frequently used on the rTAG and EE capsules, had no effect on bioavailability. It also demonstrated that the blood plasma assimilates post-prandially the phosphatidylcholine derivatives of EPA and DHA first, followed by the TAG then FFA forms. However, over the 12-week supplementation period, there was no difference in uptake and assimilation of ingested EPA and DHA into blood lipids of the uTAG, rTAG, EE, or FFA forms.

It should be noted that this study was carried out on healthy individuals and it is possible that different results would have occurred with diseased individuals, e.g., those with dyslipidemia. Also, this study did not include a phospholipid source of EPA and DHA (as found in krill oil), though the authors did comment that they would like to add this form in a future study.


  1. West AL, Burdge GC & Calder PC; “Lipid structure does not modify incorporation of EPA and DHA into blood lipids in healthy adults: a randomised-controlled trial”; British Journal of Nutrition 2016, (2), 1–10. http://doi.org/10.1017/S0007114516002713
  2. www.Nutri-facts.org, News: 28 September 2015; “Fish oil and krill oil are very similar in terms of EPA/DHA accumulation in plasma and red blood cells”. http://www.nutri-facts.org/content/nutrifacts/en_US/news/fish-oil-and-krill-oil-are-very-similar-in-terms-of-epa-dha-accu.html/p_tag/nutrifacts/news/p_tag/nutrifacts/news/inspiration/p_tag/nutrifacts/news/trends
  3. Yurko-Mauro K, Kralovec J, Bailey-Hall E, Smeberg V, Stark JG & Salem N; “Similar eicosapentaenoic acid and docosahexaenoic acid plasma levels achieved with fish oil or krill oil in a randomized double-blind four-week bioavailability study”; Lipids in Health and Disease 2015, 14: 99. DOI 10.1186/s12944-015-0109-z

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