Julie Whittington, RD

Healthy tips from a Registered Dietitian

Tuna Can Have High Levels of Mercury

Recent studies done on sushi found at sushi bars in New York City found disturbing results.  Out of 20 restaurants surveyed, five restaurants were serving tuna with high levels of mercury.  In fact, levels were so high they were above the FDA (Food and Drug Administration’s) “action level”, where the FDA can legally remove the food from the market.  According to the laboratory results, if someone were to eat six of these sushi pieces per week, the amount of ingested mercury would be above that recommended as safe by the EPA (Environmental Protection Agency).  Researchers and health professionals have commented, too, that there is no reason to believe that results would not be similar at other sushi restaurants around the US.

 

The positive thing is that many of the managers of the restaurants where the contaminated tuna was being served were shocked and immediately took action to remove the tuna from their menus.  Regular tests to check for mercury contamination are apparently not in place by the government, so you may not know if the seafood you are eating is safe or not.

 

Mercury (methylmercury) in seafood poses a threat to human health in a number of ways.  First of all, it can harm a developing nervous system.  According to the EPA, methylmercury can impact cognitive thinking, memory, attention, language and fine motor and visual spatial skills in children exposed to methylmercury in the womb.  See http://www.epa.gov/hg/effects.htm for more information.  Additionally, mercury can also pose a threat to other adults, in that it may increase the risk of cardiovascular disease and neurological problems. 

So, pregnant women, infants and children should avoid all fish with typically higher concentrations of mercury in them.  In 2004, the FDA and EPA put out specific guidelines on the safety of consuming fish while trying to become pregnant, during pregnancy, while nursing and also in young childhood.  Included in the advisory were recommendations on canned tuna, but not fresh tuna.  The 2004 recommendations included:

  • Do not eat Shark, Swordfish, King Mackerel, or Tilefish because they contain high levels of mercury.
  • Eat up to 12 ounces (2 average meals) a week of a variety of fish and shellfish that are lower in mercury.
    • Five of the most commonly eaten fish that are low in mercury are shrimp, canned light tuna, salmon, pollock, and catfish.
    • Another commonly eaten fish, albacore (“white”) tuna has more mercury than canned light tuna. So, when choosing your two meals of fish and shellfish, you may eat up to 6 ounces (one average meal) of albacore tuna per week.
  • Check local advisories about the safety of fish caught by family and friends in your local lakes, rivers, and coastal areas. If no advice is available, eat up to 6 ounces (one average meal) per week of fish you catch from local waters, but don’t consume any other fish during that week.
  • Follow these same recommendations when feeding fish and shellfish to your young child, but serve smaller portions.

As a dietitian, I support the above recommendations.  However, I also urge consumers to be more conservative.  I advise avoiding fresh tuna when trying to become pregnant, during pregnancy and while breastfeeding.  Also, I encourage consumers to not serve fresh tuna to small children.  This especially includes bluefin tuna which appears to contain the highest levels of methylmercury of all the tuna types and may not be suitable for anyone of any age.  Other fish to avoid during and surrounding pregnancy and in young childhood, in addition to those listed above are Chilean sea bass, grouper & marlin.  The following fish (of which this is not guaranteed to be an all-encompasing list) that have been found to contain medium levels of methylmercury include: freshwater bass, black cod, bluefish, croaker, grouper, North American lobster, orange roughy and Sacramento black fish. 

Care should be taken to usually select fish containing the lowest levels of potential mercury as possible. If you select a fish not in the group of lowest risk for methylmercury contamination, be sure you meet recommended guidelines for age group and life stage (i.e. pregnancy) and that you only consume the appropriate serving size.  See charts with average levels of methylmercury in fish at http://www.cfsan.fda.gov/~frf/sea-mehg.html or http://www.cfsan.fda.gov/~frf/seamehg2.html.    

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2 comments on “Tuna Can Have High Levels of Mercury

  1. Michelle Galantino
    November 22, 2008

    I have been eating tuna (about 3oz.) per day. I have been doing this for weigh loss purposes. It seems to be working. After reading your article, I will cut down. Can I break the 12 oz. up into 3 oz. 4 times a week. Is this safe?

  2. juliewhittingtonrd
    November 22, 2008

    Michelle-
    Yes, you can break up the 12oz into 3oz portions across the week.
    Know that chunk light tuna has less mercury risk than albacore tuna. Chunk light tuna is considered a “lower mercury fish”.
    Try canned salmon as an alternative, too.

    Thanks for reading,
    Julie Whittington

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This entry was posted on March 11, 2008 by in Food Safety and tagged , , , .

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