Stearidonic acid (SDA), a long-chain omega-3 fatty acid (C18:4) with a range of health benefits, could be a game-changer in supplements and foods. It offers a clean label, and it is also vegan, traceable and may offer a highly scalable pathway to meeting omega-3 recommended daily intakes. This article provides a brief overview on the basics about SDA and its rising importance in omega nutrition.
SDA in Omega-3 Metabolism
Significant dietary SDA is commercially available only from vascular plant origins, although it occurs naturally at low levels (0.5 to 2 percent, typically) in edible oily fish. Metabolically, SDA is synthesized by humans from dietary alpha-linolenic acid (ALA, C18:3), a more widely abundant omega-3 found in some seed and nut oils such as flax and chia. ALA is converted into SDA by delta-six desaturase (Δ6D), an enzyme originating in the liver. While critical to the synthesis of very long chain omega-3s, this enzymatic conversion is particularly inefficient in humans. SDA is then further converted to the widely studied and well-known omega-3 eicosapentaenoic acid (EPA, C20:5). Human cell membranes require the highly unsaturated fatty acids to be incorporated as phospholipids in order to maintain proper fluidity, porosity and integrity, and to serve as reservoirs of anti-inflammatory response mediators. While SDA is itself a product of ALA metabolism, direct dietary SDA intake offers people a much more efficient way to synthesize EPA from non-marine sources.
As such, SDA has been dubbed a “pro-EPA" omega-3 fatty acid because it bypasses the Δ6D rate-limiting step in humans that causes plant-derived ALA sources to convert poorly to the more elongated omega-3 fatty acids EPA, DPA (C22:5) and DHA (C22:6). Clinical studies have shown that while SDA does not convert to DHA to any significant degree, SDA converts to EPA in tissues and circulating cells up to five times more efficiently than ALA. Further, because SDA is less unsaturated than EPA and DHA, it is more stable, less prone to oxidation, and therefore more amenable in a wide variety of food and beverage applications where resulting “fishy" off-flavors present challenges to palatability and consumer acceptance.
SDA Commercial Supply and Sustainability
SDA came to prominent awareness in the U.S. natural products industry due to developmental work announced by Monsanto and Solae of a genetically-modified (GM) SDA-enriched soya oil in 2008 to 2010. The Monsanto product, whose commercialization rights are now owned by DSM, does not yet appear to be commercially available for human consumption. Recently, Nature’s Crops International gained regulatory approvals in the United States and European Union for refined Buglossoides arvensis seed oil (tradename: Ahiflower), which has the highest SDA content from a single non-GM plant source.
In 2013, GOED reported that in 12 industrialized countries, 220 million consumers had stopped taking marine-derived omega-3 supplements due to sustainability concerns. This is a large and expanding consumer market. More recently, in 2014 and 2015, one of the Peruvian anchoveta fisheries and the U.S. West Coast sardine fishery were closed due to concerns over fish stock levels. This is significant because the Peruvian fishery is responsible for supplying about 70 percent of the world’s omega-3 fish oil, as reported by GOED.
This event, though relatively short-lived, underscored the growing need for an “all-in" approach to supplying omega-3 fatty acids globally—from marine, algal and plant sources. Whether due to climate factors, unregulated overfishing in nearby waters, or to changes in the reproductive ecology of wild anchovy and sardines, the resulting supply chain disruptions of available fish meals to aquaculture (salmon, shrimp, etc.) and for human dietary supplement uses portend a longer-term sustainable supply concern. While the Peruvian, Moroccan, U.S. West Coast and other anchovy and sardine fisheries that are subject to intermittent population collapses can recover with proper management, diverse new omega-3 nutritional sources are needed to address long-term demand, let alone respond to consumers who cannot or choose not to eat marine animal products.
In an era of rapidly expanding middle class affluence in countries such as China, Brazil and India (with a total combined population of 2.8 billion), and with returning growth in omega-3 product demand in North America after several years of negative publicity about a purported lack of health benefits of omega-3s, demand for high-quality, high-purity omega-3 nutrition will increase steadily for the foreseeable future.
A recent industry market research report shows the global demand for omega-3 supplements will grow to US$4.48 billion by 2020 with a 13.1 percent annual growth rate. This means that SDA, a readily scalable and sustainable plant-based omega-3 source that does not rely on marine fisheries, nor on more costly algal or microbial omega-3 sources of EPA and DHA, will certainly help solve a global supply dilemma. SDA presents formulators, manufacturers and consumers an immediate and quantifiably superior alternative to current plant-derived omega 3s from flax and chia by increasing the overall effective omega-3 payload, and hence, reducing the total caloric intake and/or dosing.
SDA Clinical Science
SDA has its own emerging body of scientific and clinical research supporting health benefits that are both aligned with, and in some cases, independent of omega-3 ALA, EPA and DHA findings. This is true in topical and in ingestible SDA applications. Recent peer-reviewed published references include the following benefits or activities associated with SDA:
- Anti-aging: Topical SDA oil can increase dermal structural proteins and reduce fine lines and wrinkles, while inhibiting UV-induced inflammation.1
- Anti-obesity: SDA can suppress adipocyte (fat cell) differentiation.2
- Anti-diabetes (type 2): SDA can suppress type 2 diabetes biomarkers.3
- Anti-inflammation: Plant SDA oil decreases intestinal PGE2 sequestration and reduces endogenous production of COX-derived arachidonic acid metabolites.4
- Coronary heart disease (CHD)/cardiovascular disease (CVD) prevention: Plant SDA oil sources decrease cholesterol blood fractions and triglycerides, benefiting people at risk for CHD/CVD.5,6
- Anti-tumorigenesis: SDA reduces growth of human breast cancer cells in vitro and in vivo. SDA enhances chemosensitivity of canine lymphoid tumor cells. SDA enhances anti-tumor activity of doxorubicin in human prostate cancer cell lines.7,8,9
Long-term prospective studies in humans investigating specific health effects of SDA consumption have yet to be carried out and published. However, preliminary cell line, animal and human studies indicate that SDA has beneficial effects on various biomarkers of disease, particularly relating to CVD and inflammatory pathways, as distinct from ALA and DHA. SDA is indeed a promising “pro-EPA" omega-3 alternative, especially for vegetarians or people choosing not to consume marine or algal omega-3 sources. In the natural products industry’s efforts to respond to consumer concerns about the sustainability, traceability, purity, and sensory appeal of omega-3 nutrition sources, SDA is truly a market-responsive omega-3 fatty acid.
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