What’s Really In That Can of Tuna?

By now we’re all familiar with the warnings about mercury in fish and canned tuna fish – that deli counter staple – has been particularly targeted by these warnings because of how frequently most of us consume it. Now it seems we should be even more cautious when it comes to tuna fish as the canned variety has been found to have even more mercury than previously thought.

Consumer Reports recently tested 42 samples of tuna from cans and pouches and found that every sample contained mercury, in amounts ranging from 0.018 to 0.774 parts per million. While the FDA won’t issue a recall unless the mercury content reaches 1 ppm or more, the levels found in this test amount to more than we should consume. Just 2.5 oz of white tuna exceeds the EPA safety threshold while 5 oz of light tuna (which is generally lower in mercury than the albacore variety) would be over the limit. The levels of mercury found in white tuna were also higher than previous tests performed by the FDA in 2002-2004.

Mercury, which finds its way into our waterways from coal plants, volcanos, and other sources, accumulates in fish in the form of methylmercury. Large fish, like tuna, have higher levels of mercury because they live longer and also ingest smaller fish that contain mercury, allowing the heavy metal to build up. When we eat the fish, we ingest the mercury as well. The primary danger of overexposure to mercury is neurotoxicity. Fetuses, infants and children are  most susceptible to the effects of mercury, and it’s consumption can lead to developmental delays including impaired cognition, motor skills, memory, language, attention and visual spatial skills.

This is not to say that we should eliminate fish from our diets altogether. Fish, after all, is an important part of a healthy diet, providing a great source of protein and heart-healthy, brain-boosting omega-3 fats. Although the following guidelines for fish consumption have been established with children and women of childbearing age in mind, everyone should make low-mercury choices when possible:

  • Light tuna is usually lower in mercury than white tuna, and therefore a better choice.
  • When it comes to canned tuna, young women and children should limit their intake.
  • Children under 45 lbs should consume less than 4 oz of light tuna or 1.5 oz of white tuna per week.
  • Pregnant and breast feeding women should eliminate tuna from their diets entirely.
  • Avoid shark, swordfish, king mackerel, orange roughy, marlin, and tilefish
  • Eat up to 12 oz (~2 servings) of low-mercury fish per week. Low-mercury fish include salmon, shrimp, catfish, pollock, anchovies, crab, haddock, sardines, oysters, tilapia, and trout
  • Check with your local advisory about fish caught by family and friends in area waters
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  • My parents are long-time albacore fishermen, and we’ve been custom canning and selling their tuna for about a decade. We wanted to add one more item of things you can do to help yourself and the oceans: learn about the difference between troll-caught and long-lined albacore, and then choose troll-caught.

    Troll-caught albacore has been tested and shows mercury levels comparable to chunk light tuna (which is considered safe by the FDA).To see the results of the Oregon State University study go to http://osuseafoodlab.oregonstate.edu/hg-info.htm. The FDA does not test troll-caught and long-lined albacore separately, which results in reports of high mercury in all albacore. It’s like taking a thousand bushels of conventional corn, mixing it with a quarter bushel of organic corn, and then recommending all corn be avoided because pesticides were found in the mixed sample. (Okay, not the greatest analogy, but you get the point.)

    Similar to how conventional and organic farming both produce corn with different pesticide levels, different fishing methods consistently result in fish with different levels of mercury. Long-lining targets fish deeper in the ocean, resulting in by-catch and older fish with higher mercury levels.

    Troll-caught albacore are caught one-at-a-time by hook-and-line by people like my parents. Their 12 lures skitter near the surface of the ocean, attracting young albacore who have not had time to accumulate as much mercury in their bodies. Bycatch is almost nonexistent.

    How can you know if the albacore tuna is troll-caught? Look for:

    the MSC logo on the cans. The Marine Sustainability Council has rated our fishery sustainable.the words ‘troll-caught’ or ‘caught one-at-a-time by hook-and-line’ on the can.

    a higher fat content in the fish

    albacore canned in micro (or custom) canneries

    For more information you can visit our website http://www.WildPacificSeafood.com or http://www.PacificAlbacore.com, the trade site for the North Pacific Albacore Fishery

    Stephanie Hopkinson
    Wild Pacific Seafood

  • Not all tuna companies fish for large tuna…especially if they follow sustainable practices. Wild Planet Foods sources their tuna from the North Atlantic where the tuna are smaller, therefore much lower in mercury. They also fish using the pole and troll method which eliminates bycatch, and they only cook the tuna once in the can – meaning more Omega 3s for the body.

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