Fish Oil Supplements, EPA, DHA, and ALA: Does Your Omega-3 Source Matter?

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You've heard plenty about the merits of omega-3 fatty acids, most notably how those healthful fats protect against heart problems. Does the source from which you get them make a difference? Omega-3s are considered essential fatty acids because the body requires them but cannot make them on its own. Thus, we need to forage the supermarket—or the supplement aisle—to ensure we get enough into our diets. Fatty fish like salmon and tuna are touted as optimal sources, while vegetarians often cite the omega-3 content of flax, walnuts, and soybean or canola oils. (U.S. News has written about 11 easy ways to load up on omega-3s from food sources.) And supplements containing omega-3s derived from fish oil or algae are making a splash on store shelves and health websites.

The possibilities are enough to leave a health-conscious consumer confused. To get the skinny, U.S. News discussed omega-3s with three experts: Stephen Kopecky, professor of medicine at the Mayo Clinic; Marion Nestle, professor at New York University and Food Politics blogger; and Walter Willett, chair of the department of nutrition at the Harvard School of Public Health. Here's the expert take-away:

Learn the omega-3 acronyms: EPA, DHA, and ALA
Not all omega-3s are the same. The three main forms are eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and alpha-linolenic acid (ALA). EPA and DHA are considered long-chain forms of omega-3 and are found in fish, fish oil supplements, and algae extract. ALA, the short-chain form, is found in plant sources like walnuts, flax seed, canola and soybean oil, and, to a lesser degree, green leafy vegetables. The body needs to convert the short-chain version to a long-chain version in order to make use of it—but this conversion doesn't happen very rapidly, says Willett.

Not everyone agrees on the effectiveness of ALA versus EPA and DHA
Experts don't definitively know whether it's best to get our omega-3s from seafood sources or plant sources. "It is an unresolved question whether ALA provides the same benefit in preventing heart disease as does the very-long-chain form" of omega-3, says Willett. But based on multiple rigorous clinical trials in heart patients, Kopecky is a believer in the combination of EPA and DHA and regularly prescribes it to patients with heart disease or risk factors like hypertension or high triglycerides. It's also reasonable for people without those risk factors to take 1,000 mg (or 1 gram) per day if they don't get much EPA and DHA from their diets, he says. When looking for a supplement, he says, "the issue is not so much omega-3 but EPA and DHA"; make sure the long-chain omega-3s are in your supplements. Check the label for a 3-to-2 ratio—of either 3 parts EPA to 2 parts DHA or vice-versa (the research suggests that either ratio produces heart benefits, Kopecky says). He feels research suggesting that ALA carries the same heart health benefits is not as convincing.

What fun would the quest for health be without a bit of disagreement? "The science is tricky to interpret," says Nestle. She argues that early humans evolved in an environment—and on a diet—that did not have an abundance of fish, yet they were fit enough to survive. "I think plant sources are highly underrated and that most of the fuss about omega-3s is about marketing, not health," Nestle says.

Consider your overall diet
Before popping a supplement, take a broad look at what you eat. "Gulping down fish oil supplements after a 16-ounce steak is not the same as eating a moderate[-size] piece of well-prepared salmon," Willett says. The health benefit of fish, he suggests, is probably due, at least in part, to the fact that it often replaces an alternative protein source: red meat, which takes a toll on cardiovascular health. The real issue to consider, says Willett, is if your diet is low in both fish sources of omega-3 (EPA and DHA) and plant sources (ALA). With a diet largely devoid of all types of omega-3, your heart health may be at risk.

Fish oil supplements are pretty safe
One of the concerns about eating lots of fish or fish oil is the possibility that you will consume harmful PCBs and methyl mercury. The experts note that a Consumer Reports survey of store-bought fish oil supplements found them to be safe in that regard. But beware of overdosing. Three grams or more per day of EPA and DHA may cause excessive bleeding in certain people. The Food and Drug Administration has approved a medicine, Lovaza, which can deliver higher doses of EPA and DHA—but only with a doctor's prescription.