Towards sustainable sources for omega-3 fatty acids production

Highlights

• Demand for omega-3 nutraceuticals continues to rise.

• Current omega-3 sources are unsustainable.

• Land-based omega-3 production provides potential alternative sources.

• Microalgae could be key to sustainable omega-3 production.

Omega-3 fatty acids eicosapentaenoic acid (EPA) and docohexaenoic acid (DHA), provide significant health benefits for brain function/development and cardiovascular conditions. However, most EPA and DHA for human consumption is sourced from small fatty fish caught in coastal waters and, with depleting global fish stocks, recent research has been directed towards more sustainable sources. These include aquaculture with plant-based feeds, krill, marine microalgae, microalgae-like protists and genetically-modified plants. To meet the increasing demand for EPA and DHA, further developments are needed towards land-based sources. In particular large-scale cultivation of microalgae and plants is likely to become a reality with expected reductions in production costs, yield increasese and the adequate addressing of genetically modified food acceptance issues.

Introduction

On the basis of their proven health benefits, global demand for omega-3 fatty acids has significantly increased over the last two decades, but there is mounting concern about the sustainability of sourcing these compounds from wild fish. Figure 1 presents an overview of different sources of omega-3 fatty acids and how they link to the food and supply chain. In this review, we present alternative sources of omega-3 fatty acids and discuss recent developments towards their sustainable production.

Very long chain polyunsaturated fatty acids (VLC-PUFAs), are fatty acids (FAs) of ≥20 carbons in length and at least two conjugated double bonds in the cis position. VLC-PUFAs are divided into two main groups, omega-3 (ω-3) and omega-6 (ω-6), which are distinguished by the first double bond position counted from the methyl end at carbon 3 and 6, respectively [1]. Nutritionally, C20:5 eicosapentaenoic acid (EPA) and C22:6 docohexaenoic acid (DHA) are the most important VLC-PUFAs belonging to the ω-3 family. Out of the ω-6 family, C18:2 linoleic acid (LA) [2] and C20:4 arachidonic acid (AA) [3] have also been shown to have health benefits. There is a considerable amount of research that supports the beneficial health properties of VLC-PUFAs, particularly the ω-3 FAs [4].

VLC-PUFAs are essential constituents of higher vertebrate membranes, particularly neuronal cells in humans [5]. The consumption of EPA and DHA has been reported to prevent and support cardiovascular, nervous systems and inflammatory conditions. Regarding cardiovascular benefits by regular consumption of ω-3, hypertension risk, cardiac arrhythmia, myocardial infarction and thrombosis can be reduced [4]. They exhibit positive effects on brain function [6], healthy development of the fetal brain [7] and as such are commonly included in infant formula. They have also been related with alleviation of depression symptoms [8] and post natal depression [9]. Contributions to the immune-modulatory effects, such as treating Crohn's disease, psoriasis, rheumatoid arthritis, ulcerative colitis, cystic fibrosis and lupus have also been made [10^•].

However, present average daily intakes of EPA and DHA for most people is well below the recommended doses and there is growing concern about the sources that are often viewed as unsustainable and unable to meet future demands [11]. Wild fish has been the most common source of EPA and DHA for human consumption in the last decades [12] and is at great risk of being overfished [13]. The global demand for wild fish is now much larger than the oceans can sustain [14]. The Food and Agriculture Organization (FAO) reported in 2008 that nearly 53% of marine fish stocks were close to be entirely exploited, 28% overexploited and 3% depleted or recuperating from depletion (1%) [15]. Populations of some fish have been deflated to only 10% and over 100 species have been already confirmed extinct in the ocean [16]. Worldwide fish stocks could be depleted within 40 years if harvests continue at the current rate [4]. Concern about the ability and sustainability of wild fisheries to meet increasing demand of VLC-PUFAs has moved efforts towards land-based production, including farmed fish, genetically modified plants, and large-scale production of microalgae [1] (Figure 1). The estimated market value of packaged products containing omega-3 has been estimated to reach $34.7 billion by 2016 [17^••].