July 2014 Issue
Spotlight on Stearidonic Acid — Learn More About This Alternative Omega-3 Fatty Acid
By Amelia R. Sherry
Today’s Dietitian
Vol. 16 No. 7 P. 18
Despite recommendations from the American Heart Association and other health organizations regarding omega-3 fatty acid intake, a significant number of Americans are consuming less than one-half of the recommended 8 oz of fish per week—or the 250 mg of EPA and DHA per day.1,2 This shortfall can be considered even more dramatic for individuals with cardiovascular disease (CVD) and those battling elevated triglycerides, for whom a daily dose of 1 g of EPA and DHA and 2 to 4 g of EPA and DHA, respectively, are recommended—nearly 10 to 20 times the amounts currently consumed.3
In addition to eating fish twice per week, many dietitians recommend consuming foods rich in alpha-linolenic acid (ALA), a long-chain fatty acid precursor found in plant foods such as ground flax to help boost omega-3 intake. RDs also may suggest supplements if clients and patients can’t consume the recommended amounts through diet alone, have high triglycerides, or avoid fish due to concerns about mercury content or other reasons.
To increase omega-3 fatty acid intake, food manufacturers are fortifying eggs and milk with these acids. One omega-3 they’re particularly focusing on is stearidonic acid (SDA), which is expected to appear on store shelves in soybean oil derived from genetically modified (GM) soybeans.
What Is SDA?
Like ALA, SDA is a shorter long-chain omega-3 fatty acid composed of 18 carbons, making it a precursor to longer long-chain fatty acids such as EPA and DHA. Unlike ALA, SDA has four double bonds existing at the third, sixth, ninth, and 12th carbons and, more notably, it doesn’t require the rate-limiting enzyme desaturase to convert to a longer chain fatty acid.4
Considered an omega-3 fatty acid to watch, SDA is emerging as an alternative nonfish source of omega-3s for at least two reasons. While ALA-rich foods often are recommended as an additional or alternative source of omega-3s for those who don’t or can’t consume fish, most dietitians know that the conversion of ALA to longer long-chain fatty acids is inefficient. Specifically, it’s estimated that anywhere from less than 5% to 21% of ALA converts to EPA (with sex and omega-6 intake impacting the amount), while less than 1% to 9% of ALA converts to DHA.4-7
By comparison, an increasing number of studies, largely funded by Monsanto, developer of the genetically engineered SDA-enriched soybean oil, are showing SDA to have a superior ability to convert to EPA over ALA. For example, foods supplemented with SDA-enriched soybean oil were found to raise EPA concentrations in red blood cell membranes with approximately 17% to 41% of the efficiency of EPA on a gram-for-gram basis, a conversion efficiency three to five times higher than that of ALA.7 Moreover, a meta-analysis reported that EPA levels in red blood cells were twice as high when subjects consumed SDA compared with ALA.8
In a 2009 review article on SDA research, Jay Whelan, PhD, MPH, a professor and the head of the department of nutrition at the University of Tennessee, concluded that while SDA may not replace fish as a dietary source of omega-3 long-chain fatty acids, it may be a prominent substitute for EPA in foods fortified with omega-3 polyunsaturated fatty acids. Whelan supported his conclusion by referring to evidence demonstrating that SDA consumption leads to a fivefold increase in EPA levels in plasma, neutrophil, heart, and erythrocyte phospholipids.9
Whelan’s review also suggested that SDA doesn’t affect DHA levels, which is in line with more recent studies. “SDA can be converted to EPA and, theoretically, EPA can be converted to DHA,” he explains. “In reality, only DHA changes DHA in the tissues when consuming a typical Western diet,” which is why he doesn’t advocate consuming SDA-fortified foods in place of fish or fish oils containing both EPA and DHA.
A second reason SDA likely is attracting the interest of food scientists as a potential source of omega-3s is that it’s less unsaturated than EPA, making it more stable in foods.9 Since SDA is less susceptible to oxidation, “it’s less likely to be prone to ‘off’ flavors,” Whelan says.
Dietary Sources
A limited number of foods contain small amounts of SDA, including some seed oils, such as hemp and Echium; certain fish, such as sardines and herring; and algae. To date, the American diet contains such low amounts of SDA that it hasn’t been measured.8 Of course, if genetically modified, SDA-enriched soybeans and soybean oil hit the consumer market, this may change—and it looks like it will.
In 2009, Monsanto obtained Generally Recognized as Safe status from the FDA for SDA-enriched omega-3 soybean oil.10 In April 2013, the company announced a combined effort with DSM Nutritional Products to bring the SDA-enriched soybean oil to the marketplace. Monsanto will sell its SDA-enriched soybean seeds to farmers, and DSM Nutritional Products will have “the exclusive global rights to brand, market, package, and sell the SDA soybean oil to the food industry.”11
Richard S. Wilkes, CFS, director of food applications for Monsanto, says the oil was created by inserting an enzyme responsible for increasing the conversion of ALA in soybean oil to SDA, which then is extracted from the seeds. Since soybean oil already is added to various foods, Wilkes considers it an efficient way to bring SDA to consumers. Specifically, it can be used in dairy and soy beverages, dressings, granola bars, margarine-type spreads, mayonnaise, peanut butter, smoothies, yogurt, and yogurt drinks.
As of this writing, neither Monsanto nor DSM Nutritional Products has confirmed when products containing the oil will hit store shelves.
Impact on Overall Health
In addition to raising EPA levels, some research has shown that SDA reduces elevated triglycerides. However, further comparative studies on healthy and unhealthy individuals are needed before researchers can consider SDA a potent protector of cardiovascular health.12,13
Moreover, questions remain about how SDA’s inability to raise DHA levels may impact overall health. “We’re playing with fatty acids that affect localized, cell-specific, hormonelike activity and play somewhat differing roles in disease,” says Libby Mills, MS, RDN, LDN, a spokesperson for the Academy of Nutrition and Dietetics (the Academy). “We know that EPA works primarily on inflammation, while DHA increases permeability of cell membranes, which is especially important for pregnant women and children’s brain development, and reduces atherosclerosis by blocking LDL from getting into vessels. What we don’t know is what the long-term effects of playing with the ratio of EPA and DHA may be.”
Gretchen K. Vannice, MS, RDN, author of the Omega-3 Handbook and coauthor of the Academy’s position paper on dietary fatty acids, raises additional concerns about how SDA-enriched soybean oil products will be marketed to consumers. If foods are labeled as a general source of omega-3s, for example, this could lead to problems. “It’s important that people know that if they choose to eat food products containing SDA-enriched soybean oil, they will not get DHA. This is critical information for the elderly and women who are pregnant and lactating, since DHA is important for infant development, cognitive health, and vision maintenance, in addition to heart health,” she explains. “When food manufacturers take the product to market, they should be very clear that SDA-enriched soybean oils give zero DHA.”
Who Can Benefit From SDA?
Theoretically, the same individuals who rely on ALA-containing foods to increase their omega-3 intake may benefit from adding SDA to their diet. This includes vegetarians, vegans, and anyone else who consumes little to no fish.
In practice, turning to food products containing SDA-enriched soybean oil to help clients and patients reach recommended levels of omega-3s may not make much sense, according to Mills. “Overall, too many calories are already coming from dietary fat,” she says, adding that dietary fat consumption in the United States has increased by two-thirds since the 1950s. Based on conversion rates in studies, clients and patients need up to nine times the amount of SDA as EPA to reach recommended intakes, “which means eating a lot of extra fat from oil or getting very little EPA,” she says.
Counseling Tips
It’s important for clients, patients, and consumers to know that if they choose to eat food products containing SDA-enriched soybean oil, it’s a GM product that provides limited amounts of EPA and no DHA. RDs looking for an alternative source of omega-3s for vegetarian and vegan clients and patients can recommend algae-derived supplements containing both EPA and DHA, Vannice says.
For people who ask whether they should consume products containing SDA-enriched soybean oil to lower their heart disease risk, dietitians can suggest they eat more anti-inflammatory foods and spices containing ALA and phytochemicals, such as cruciferous vegetables, complex carbohydrates, blueberries, turmeric, and ginger, to receive the same health benefits without adding extra fat and oils to their diet, Mills says. “We also can recommend avoiding excess consumption of alcohol, sugar, and refined grains as well as behaviors such as smoking, which all contribute to inflammation,” she says.
Bottom Line
As new omega-3 fortified foods hit store shelves, dietitians should be prepared to counsel clients and patients about reading ingredient labels to learn the source of these fats. If SDA-enriched soybean oil is listed, dietitians should explain that it’s derived from GM soybeans, and that it may raise EPA levels but won’t provide DHA.
For the elderly and pregnant and lactating women, RDs should further explain why DHA is important. For overweight patients and those at risk of CVD, RDs should mention that high amounts of the food product would need to be consumed—along with unnecessary fat and calories—to get significant amounts of EPA.
For all clients and patients, traditional sources of omega-3 fatty acids, such as oily fish, fish oil supplements, and algae-derived supplements, still should be consumed to reach recommended EPA and DHA intake.
— Amelia R. Sherry is a freelance writer, graduate nutrition student, and founder of the blog FeedingIsla.com.
References
1. US Department of Agriculture, US Department of Health and Human Services. Dietary Guidelines for Americans, 2010. 7th ed. Washington, DC: US Government Printing Office; 2010.
2. Papanikolaou Y, Brooks J, Reider C, Fulgoni VL 3rd. U.S. adults are not meeting recommended levels for fish and omega-3 fatty acid intake: results of an analysis using observational data from NHANES 2003-2008. Nutr J. 2014;13:31. doi: 10.1186/1475-2891-13-31.
3. Fish 101. American Heart Association website. http://www.heart.org/HEARTORG/GettingHealthy/NutritionCenter/Fish-101_UCM_305986_Article.jsp. Updated February 21, 2014. Accessed April 20, 2014.
4. Vannice G, Rasmussen H. Position of the Academy of Nutrition and Dietetics: dietary fatty acids for healthy adults. J Acad Nutr Diet. 2014:114(1):136-153.
5. Davis BC, Kris-Etherton PM. Achieving optimal essential fatty acid status in vegetarians: current knowledge and practical implications. Am J Clin Nutr. 2003;78(3 Suppl):640S-646S.
6. Burdge G. Alpha-linolenic acid metabolism in men and women: nutritional and biological implications. Curr Opin Clin Nutr Metab Care. 2004;7(2):137-144.
7. Lemke SL, Maki KC, Hughes G, et al. Consumption of stearidonic acid-rich oil in foods increases red blood cell eicosapentaenoic acid. J Acad Nutr Diet. 2013;113(8):1044-1056.
8. Walker CG, Jebb SA, Calder PC. Stearidonic acid as a supplemental source of ω-3 polyunsaturated fatty acids to enhance status for improved human health. Nutrition. 2013;29(2):363-369.
9. Whelan J. Dietary stearidonic acid is a long chain (n-3) polyunsaturated fatty acid with potential health benefits. J Nutr. 2009;139(1):5-10.
10. GRAS notices: GRN No. 283. US Food and Drug Administration website. http://www.accessdata.fda.gov/scripts/fdcc/index.cfm?set=GRASNotices&id=283. Accessed April 12, 2014.
11. DSM Nutritional Products and Monsanto Company partner to deliver first SDA omega-3 soybean oil for use in foods in North America. Monsanto Company website. http://www.monsanto.com/global/uk/newsviews/pages/first-sda-soybean-oil-in-north-america.aspx. Updated April 8, 2013. Last updated May 12, 2014. Accessed April 12, 2014.
12. Forrest LM, Lough CM, Chung S, et al. Echium oil reduces plasma triglycerides by increasing intravascular lipolysis in apoB100-only low density lipoprotein (LDL) receptor knockout mice. Nutrients. 2013;5(7):2629-2645.
13. Surette ME, Edens M, Chilton FH, Tramposch KM. Dietary echium oil increases plasma and neutrophil long-chain (n-3) fatty acids and lowers serum triacylglycerols in hypertriglyceridemic humans. J Nutr. 2004;134(6):1406-1411.