Science & the Public

Janet Raloff
Science & the Public

Fishy fat from soy is headed for U.S. dinner tables

For most Americans, it could help redress a critical shortfall in a beneficial nutrient

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WASHINGTON, D.C. Most people have heard about omega-3 fatty acids, the primary constituents of fish oil. Stearidonic acid, one of those omega-3s, is hardly a household term. But it should become one, researchers argued this week at the 2011 Experimental Biology meeting.

In any case, stearidonic acid should at least become a welcome constituent of kitchen larders. The scientists’ reasoning: This fatty acid can provide fish oil’s heart and other health benefits – without the fishy taste or high cost of finned fare. Beginning next year, it also can be supplied without harming a single fish.

Numerous health organizations advocate that Americans down at least two fish meals a week, notes Eileen Kennedy, dean of Tufts University’s Friedman School of Nutrition Science and Policy in Boston. This emphasis on seafood is not because nutritionists prize fish, per se, she says, so much their wanting to see consumers get more of two long-chain omega-3’s in the animals’ oil: eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA).

“The American diet, as typically consumed, is low in omega-3 fatty acids,” Kennedy says. And the recently released federal nutrition guidelines not only recommend consuming a variety of fish and shellfish species, but also set a weekly target of eating some 8 ounces of seafood. Pregnant women, she notes, are being advised to eat up to 12 ounces per week.

But consumers are also being cautioned to choose that seafood wisely, because fish can unwittingly bring toxic methyl mercury to the dinner table. “So this [fish recommendation] gets to be a challenge to communicate,” observes Kennedy, who co-chaired an April 8 symposium on dietary omega-3 sources and benefits at the conference.

To date, toxic intakes of fish have not emerged as a big problem, but that’s largely because few Americans come close to meeting the recommended fish intake. Most people fall about 75 percent short of the national goal.

Against this backdrop, SDA-enriched soybean oil is very attractive, Kennedy says. It can be incorporated in a range of foods without affecting taste (I can vouch for that, having eaten an SDA-soy-oil laced muffin at the meeting). Moreover, if and when SDA-enriched oil becomes available, it should cost less than fish-oil capsules (some of which have been found contaminated with pesticides, dioxins and other toxic pollutants), and run just a small fraction of the price of getting an equivalent amount of omega-3s from eating fish.

However, even if consumers wanted to get their omega-3 intake from downing fish, there are growing concerns about how that might be achieved. Indeed, argued William Banz of Southern Illinois University in Carbondale, “there’s not enough fish in the sea.”

And what about people who don’t like the taste of oily marine fish – the species rich in EPA and DHA – or who live too far from the coast to make seafood readily available, asks William Harris, director of cardiovascular research at the University of South Dakota’s Sanford School of Medicine. For them, substituting the SDA product for some of the oils in prepared foods could be viewed as a healthful fortification program. “Like adding iodine to salt,” he said.

Commercial soy-derived SDA on its way
Right now, the only sources of EPA and DHA are marine micro-algae and the fish that move these algal fats up the food chain. “As the availability of fish decreases, we’ve got to think of other sources for omega-3 fatty acids,” says Richard Deckelbaum, director of Columbia University’s Institute of Human Nutrition in New York City.

That’s yet another reason why Kennedy says of SDA: “I hope it’s on the market soon.”

And it will be, probably by 2012, says nutritionist Ratna Mukherjea with Solae in St. Louis. Her company plans to market foods fortified with SDA.

The commercial ag giant Monsanto inserted genes for two enzymes – one derived from a flower (Primula juliae), the other from a red bread mold (Neurospora crassa) – into a line of soybeans. Although some people object to the biotech manipulation of genes in food crops, this is far from the first genetic manipulation of soy, Deckelbaum observes. Already, he points out, some 70 percent of ordinary U.S. soybeans are genetically modified for some trait or another.

The two enzymes Monsanto has just added to soy effectively turn the legume’s oil into a proto fish oil.

Many plants make alpha linolenic acid (or ALA), a botanical omega-3. The human body possesses enzymes to elongate ALA into the useful EPA, but the process isn’t efficient, Harris explains. Only about a tenth to one percent of any ingested ALA molecules will chemically morph over time into an EPA.

Monsanto’s genetically engineered soybeans can turn their ALA into SDA. Human enzymes can lengthen SDA into EPA fairly readily. There are efficiency losses in making that conversion, he acknowledges. His team has showed that it takes about four to five times more SDA to get the same EPA values in the blood as would develop if people took in EPA directly from fish or fish-oil capsules.

Two years ago, Monsanto petitioned the Food and Drug Administration to have their SDA-enriched soy oil granted generally recognized as safe – or GRAS – status. That petition noted the company’s intent “to market SDA soybean oil as a food ingredient in the United States in a variety of food products including baked goods and baking mixes, breakfast cereals and grains, cheeses, dairy product analogs, fats and oils, fish products, frozen dairy desserts and mixes, grain products and pastas, gravies and sauces, meat products, milk products, nuts and nut products, poultry products, processed fruit juices, processed vegetable products, puddings and fillings, snack foods, soft candy, and soups and soup mixes.”

Oily fish already supply SDA to the diet, and conventional fish-oil supplements contain roughly 1 to 3 percent of this fatty acid, Monsanto noted. Certain boutique oils from edible plant seeds, notably black current and “noxious weed” Echium, also contain substantial amounts of SDA. Monsanto said it planned to fortify foods with enough of its soy product to provide 375 milligrams of SDA per serving.

Last year, FDA granted GRAS status to SDA-enriched soy, so Solae now can legally incorporate the oil into foods. But there remains a wrinkle. FDA has not yet granted Monsanto permission to grow this genetically modified line of soybeans in open fields. That’s expected next year.

If the company succeeds in gaining that anticipated approval, Harris says, each acre planted with the new line of legumes could yield omega-3 quantities equal to that provided by some 10,000 3-ounce servings of salmon.

By the way, I asked some of the speakers about potential conflicts of interest. Harris has consulted to developers of SDA-enriched soy oil but no stock in the enterprises. Kennedy is on a Solae scientific advisory panel, but has no financial ties. And Deckelbaum said he had no ties.

Citations

W.S. Harris, et al. Stearidonic acid-enriched soybean oil increased the omega-3 index, an emerging cardiovascular risk marker. Lipids, Vol. 43, September 2008, p. 805. doi: 10.1007/s11745-008-3215-0. Abstract: [Go to]


J. Raloff. Is your fish oil polluted? Science News blog. November 20, 2008. [Go to]


J. Whelan. Dietary stearidonic acid is a long chain (n-3) polyunsaturated fatty acid with potential health benefits. Journal of Nutrition, Vol. 139, January 2009, p. 5. doi: 10.3945/​jn.108.094268. Abstract: [Go to]


University of Maryland. Omega-3 fatty acids web page. [Go to]


Harvard School of Public Health. Omega-3 Fatty Acids: An Essential Contribution. [Go to]


Monsanto Co. GRAS Notice for Stearidonic (SDA) Omega-3 Soybean Oil. Filed February 25, 2009. [Go to]

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