Better Fish Swimming

Published on September 4th, 2012 | by Tanya Sitton

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New Study: Eating Fish for Heart Health? Not So Fast!

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fish swimming in a blue seascape

A new study suggests that mercury and omega-3s affect heart health in contradictory ways, making fish a less-than-ideal source for these healthy fatty acids. To skip the mercury, skip the intermediary: go directly to the source! Plant-based omega-3s provide the same heart health benefits, but without the mercury — and without the environmental devastation or unnecessary suffering and death, while we’re at it. What a bargain!

New Study: Mercury in Fish Appears to Reduce Omega-3 Benefits

Mercury is a highly toxic element known to cause neurological and other health problems in humans, at even low or moderate levels of exposure. Due to environmental contamination combined with naturally occuring forms of mercury, it’s found in virtually all fish and shellfish. Seawater itself contains low levels of this toxic metal; but aquatic species absorb mercury much more easily than they can excrete it, so it accumulates in the bodies of fish and shellfish over the course of their lifetimes.

As reported by Reuters earlier this week,

Omega-3 fatty acids and mercury, both found in fish, appear to have opposite  effects on heart health, according to a northern European study.

Researchers, whose conclusions were published in the American Journal of  Clinical Nutrition, looked at data from more than 1,600 men from Sweden and  Finland to find that men with high levels of mercury in their body had an  increased risk of heart attacks, while those with a high concentration of  omega-3s had a lower risk…

The men in the study submitted hair and blood samples to measure their mercury  and omega-3 levels, as well as information on their health and lifestyle…

The researchers found that men with at least 3 micrograms of mercury per gram of  hair had a somewhat increased risk of heart attacks compared with men with 1  micro-gram per gram. But this only held true if the men also had low levels of omega-3 fats. For men  with more of the fats, it took higher levels of mercury to see an increased  heart-attack risk, suggesting the two compounds might have opposite effects on  the heart.

Researchers point out that a cause-effect relationship between mercury and heart attacks is yet to be established. However, this study does suggest that mercury may increase risk for cardiac events, and inhibit the otherwise beneficial effects of omega-3 consumption.

Health organizations like the American Heart Association and the Mayo Clinic have traditionally recommended about 2 servings of fish per week, as a good way to get omega-3 fats for improved heart health. Even for fish-eaters, though, supplementation is often recommended for optimal benefit. According to the Mayo Clinic, “Omega-3 fatty acids may decrease triglycerides, lower blood pressure, reduce blood clotting, boost immunity and improve arthritis symptoms, and in children may improve learning ability.” They also appear to lower heart disease risk, especially risk from sudden cardiac death.

But it’s the omega-3 fats that do all this good stuff: not the fish flesh itself!

This new study, combined with the environmental and ethical considerations surrounding seafood consumption, highlights the eminent sensibility of skipping the ‘middle man’ and going straight to the source.

Get Omega-3s Where the Fish Do: Plants!

Vegan dietician Ginny Messina offers this advice about omega-3 sources:

Flaxseeds and a handful of other plant foods provide an omega-3 fat called alpha-linolenic acid or LNA which is an essential nutrient. This means it is absolutely necessary in your diet. Best sources for vegans are flaxseed and flax oil, chia seeds, hempseed oil, walnuts or walnut oil, canola oil, and full fat soyfoods. You can check the vegan food guide to see how much of these foods to eat. (The information is in the bottom right section of the guide.)

The other omega-3 fats are DHA and EPA, two closely-related fats typically found in fatty fish, and to a lesser extent in some sea vegetables. They are not considered essential nutrients because humans can synthesize these fats from LNA. Whether we can make enough for optimal health is a big question, though. Vegans have lower blood levels of these fats than people who eat fish, but how much this matters remains unclear. The jury is still out on the health benefits of DHA and EPA intake. These fats may protect against heart disease as well as dementia and depression, but the findings are conflicting. The good news is that if you choose to take supplements of DHA and EPA (and I do), there are vegan sources derived from algae.

RD Jack Norris provides an excellent analysis and explanation of exactly how much is enough, when it comes to omega-3s, concluding with the following recommendations:

Following all three of these recommendations should keep vegans on par with fish eaters:

1. Take a DHA Supplement

Under 60 years old: 200 – 300 mg every 2-3 days         60+ years old: 200 – 300 mg per day

2. Do not prepare food with oils high in omega-6 such as corn, soy, safflower, sunflower, most vegetable oil blends (typically labeled “vegetable oil”) and sesame oil. Instead, use low omega-6 oils like olive, avocado, peanut, or canola.

3. On average, vegetarians meet about 50 to 60% of the daily ALA recommendations without special diet planning and should add 0.5 g of uncooked ALA daily. This would be the equivalent of:

1/5 oz *English walnuts (3 halves) 1/4 tsp of flaxseed oil 1 tsp of canola oil 1 tsp ground flaxseeds

*English walnuts are the typical walnuts for sale in grocery stores. They are distinct from black walnuts.

Too much omega-3 can result in bleeding and bruising. If you have reason to believe you have problems with easy bleeding or bruising consult a health professional before increasing your omega-3 intake.

By following these guidelines we can reap the benefits of omega-3 consumption, without the complications that mercury brings to the table.

Keep the Omega-3s, Ditch the Mercury!

This new study suggests that if you eat fish for your omega-3′s, the mercury you’re also eating may limit the heart health benefits you’d otherwise expect to enjoy.

Fish get omega-3s from the algae they eat. By choosing not to run these healthy fats through the bodies of fish before eating them, we can get all the health benefits without any of the mercury risks. With that approach, we also avoid supporting decimation of ocean ecosystems and the unnecessary infliction of suffering and death — not only upon commercially fished species, but on the millions of non-targeted fish, sea turtles, and aquatic mammals routinely killed and discarded as ‘bycatch’.

No contest: I’ll take the plant-based omega-3s, please!

Food for Further Thought

To learn more about why and how to opt out of seafood consumption, and get those great omega-3 fats elsewhere, surf these resources:

Image credit: Creative Commons photo by Tim Pearce.

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About the Author

is an ecovore, veganist, messy chef, green girl, food revolutionary, and general free-thinkin' rabble-rouser. M.S. in a health profession, with strong interests in biology, nutrition, and healthy living - find her on .



  • John L. Farthing

    Excellent article! Well documented—clearly, energetically expressed… The argument about where we should get our Omega-3s reminds me of discussions about how humans should obtain the protein they need. Since it takes ten pounds (or more) of vegetable protein to produce one pound of protein from slaughtered animals, how can it make sense–in a protein-deficient global population–to get our protein from animal sources? We can our get protein from the same place where cows and pigs and chickens get theirs, with far less environmental damage and cruelty to farm animals… It’s insane to lose 90% of the available protein by processing it through the bodies of farm animals. When the ethical and environmental costs are factored in, this quickly becomes no-brainer. In the same way, if we can get what our bodies need from the same vegetable sources that make fish so rich in Omega-3s, the obvious conclusion—not only from an ecological and ethical perspective but also from a desire to avoid mercury poisoning—is that we can and should get our Omega-3s directly from vegetable sources, not indirectly through the consumption of the dead flesh of fish and other seafood.

    • http://www.faunahope.org Tanya Sitton

      Thanks so much for reading, and for sharing your thoughts! One thing that keeps cropping up (ha! plant-based pun, yay!) with vegan eating, for me, is how often the health/ environment/ ethics factors all coalesce into one lovely package. :)

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