Omega-3 Long-Chain Polyunsaturated Fatty Acids, EPA and DHA: Bridging the Gap between Supply and Demand

Abstract

The omega-3 (n-3) long-chain polyunsaturated fatty acids (LC-PUFA), eicosapentaenoic (EPA, 20:5n-3) and docosahexaenoic (DHA, 22:6n-3) acids, are well accepted as being essential components of a healthy, balanced diet, having beneficial effects on development and in mitigating a range of pathological conditions. However, their global supply from all the traditional sources of these nutrients is insufficient to satisfy human nutritional requirements. For two decades there has been considerable research carried out into all possible alternatives to the main sources of n-3 LC-PUFA, marine fish oil and fishmeal, driven largely by the aquaculture sector, as both the major user and provider of EPA and DHA. In the last few years these efforts have focused increasingly on the development of entirely new supplies of n-3 LC-PUFA produced de novo. Recently, this has resulted in various new sources of EPA and/or DHA that are already available or likely to available in the near future. In this short review, we briefly summaries the current gap between supply and demand of EPA and DHA for human requirements, the role of aquaculture in providing n-3 LC-PUFA to human consumers, the range of potential novel sources, and suggest how these new products could be used effectively. We conclude that all the new sources have potentially important roles to play in increasing the supply of n-3 LC-PUFA so that they are available more widely and in higher concentrations providing more options and opportunities for human consumers to obtain sufficient EPA and DHA to support more healthy, balanced diets.

Keywords: aquaculture; docosahexaenoic acid; eicosapentaenoic acid; genetic modification; microalgae; novel sources; oilseed crops.

Figure 1

Pathways of long-chain polyunsaturated fatty acid biosynthesis in humans and fish. All activities other than Δ4 desaturation (Δ4 Fad) are present in humans. Similarly, all activities have been demonstrated in teleost fish species, although not all species express all activities. The presence of Δ4 Fad enabling direct production of 22:6n-3 from 22:5n-3 has only been demonstrated in a few teleost fish species and, therefore, DHA (22:6n-3) production from EPA (20:5n-3) in most fish species and humans is only possible via the Sprecher shunt [1]. Δ4 Fad, Δ5 Fad and Δ6 Fad, fatty acyl desaturases; DHA, docosahexaenoic acid; EPA, eicosapentaenoic acid; Elovl2, Elovl4 and Elovl5, fatty acid elongases. Reproduced by permission from Tocher [2].

Figure 2

Content of n-3 long-chain polyunsaturated fatty acids (LC-PUFA) in flesh of Scottish farmed Atlantic salmon (Salmo salar) in 2006, 2010 and 2015, and in wild Atlantic and Pacific (Sockeye, Oncorhynchus nerka and Keta, Oncorhynchus keta) salmon. Data are presented as g n-3 LC-PUFA per 100 g flesh and are means ± SD and are taken from Sprague et al. [31,33,34].

Figure 3

Content of n-3 long-chain polyunsaturated fatty acids (LC-PUFA) in flesh of fish species common in seafood markets including oily species, Atlantic mackerel (Scomber scombrus), sardine (Sardina pilchardus) and rainbow trout (Oncorhynchus mykiss); marine species, Atlantic cod (Gadus morhua), Atlantic haddock (Melanogrammus aeglefinus), European hake (Merluccius merluccius), European sea bass (Dicentrarchus labrax), gilthead sea bream (Sparus aurata) and Yellowfin tuna (Thunnus albacares); freshwater species, common carp (Cyprinus carpio), basa (Pangasius bocourti) and tilapia (Oreochromis niloticus). Data are presented as g n-3 LC-PUFA per 100 g flesh and are means ± SD and are taken from Sprague et al. [33,34] and Sprague (unpublished data). Bar colour denotes whether the analysis was of farmed (black) or wild (grey) samples.