Does Eating Fish Really Increase Your Mercury Levels?

by Chris Centeno, MD /

fish mercury levels

One thing everyone seems to agree on is that eating fish is healthy, but many also say that because of current fish mercury levels, eating fish can increase the mercury levels in your own body and that this can cause many harmful health problems. Eat fish, just don’t eat too much—that’s the plug.

There are infographics online that list fish species that have the least amount of mercury contamination (e.g., catfish, oysters, and tilapia) and the highest amount of mercury contamination (e.g., swordfish, orange roughy, and tuna). You can print wallet cards to carry with you so you’ll always have how much fish you should eat, what type, and how often right at your fingertips. There are even apps you can pull up right on your smartphone to measure mercury levels in your sushi. But is all this really necessary? Is eating a little extra fish every now and then really all that bad?

The Fish Mercury Connection

The mere mention of mercury takes many of us back to middle-school science class. The mercury on the periodic table (Hg, number 80) is the same mercury that makes its way into our lakes, rivers, and oceans. Mercury is an element found naturally in the environment, and both natural sources, such as volcanic eruptions, and unnatural sources, such as industrial emissions and intentional dumping, are responsible for its presence in our bodies of water.

Once in the water, a complex chemical process converts mercury to methylmercury, the mercury found in our fish, and there are many theories as to how this happens. Scientists are even looking at the possibility that methylmercury is generated by a specific layer in the ocean itself. However it happens, our fish consume it, and we, in turn, consume our fish.

This leads us back to our presenting question: does eating fish really increase your mercury levels? If so, is this a bad thing?

Mercury Study on the Brain

A recent study looked at whether eating fish increased mercury levels, and if so, whether or not it resulted in a brain pathology, or disease, such as Alzheimer’s disease, Lewy bodies, and cerebral infarctions. The study looked at 554 deceased elderly participants with a mean age of 89.9. Via a questionnaire, seafood consumption was first measured about 4.5 years prior to death. Researchers autopsied 286 brains, and they found that the brains did indeed have mercury levels consistent with the amount of seafood consumed. For example, people who ate more fish had more mercury in the brain. The researchers expected to find that this, of course, meant that these moderate-to-high fish-consumption people had more brain problems.

However, the surprise finding of the study was that people who consumed moderate amounts of seafood, in fact, showed less Alzheimer’s disease pathology! So while this study answers our question—yes, eating fish really does increase our mercury levels—there was no association between those higher levels of mercury and brain problems. In fact it went the other way, showing less potential for Alzheimer’s disease.

The upshot? While you wouldn’t want to bet the bank on the results of one study, the results are likely important. The health benefits of fish are undeniable, and the concern for mercury’s impact on our environment and fish supply isn’t going to subside anytime soon. Everything in moderation and that includes eating fish mercury and all. So don’t sweat that extra tuna steak or sushi roll and there’s likely no need to buy that smartphone app!

Category: Diet/Nutrition

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12 thoughts on “Does Eating Fish Really Increase Your Mercury Levels?

  1. Judith Farrell

    I eat a lot of fresh fish, only the best kind and not farmed and I do not have high levels of mercury in my blood, as a matter of fact I was tested for toxins not long ago and all was clear. Farm fish is not good but it is not as bad as they say either. fish is good for you and as long as you get it from a good market or producer no problems. i shop at Whole Foods a little more expensive but good fish and meats. I also find Costco’s fish is good, frozen and well kept.

    1. Regenexx Team Post author

      Judith,
      Fish is very good for you, and source as you say, is very important, whether we’re talking about fish or fish oil. But if you eat that much fish, do get tested yearly, as sometimes even reputable sources change.

  2. mary ellen

    So I should not eat a starkist tuna packet every day for lunch?

    1. Regenexx Team Post author

      Mary Ellen,
      Probably not everyday, as the canning process removes a lot of the Omega 3’s which have some protective qualities from the negative affects of Mercury.

  3. SANDRA O'DONNELL

    DR CENTENO, I AGREE WITH THE FISH/MERCURY ISSUE. I DO NOT EAT MUCH FISH BUT WHEN WILD SALMON OR HALIBUT IS IN SEASON AND IS FRESH AND NON-FROZEN, I WILL HAVE IT. I WILL ALSO ENJOY SHELLFISH, WHICH IS LOWER IN MERCURY.ARINE MY omega 3 has CALAMARINE OIL– I DON’T USE FISH OIL ANY MORE.. I LIKE YOUR COMMENTS!

    1. Regenexx Team Post author

      Sandra,
      Thanks! Good fresh fish and seafood in season are wonderful, especially if you know the source!

  4. Bob G.

    @ CB

    “Not to mention that we have decimated 75% of the world’s fish population, used the extinction of many species and have completely disrupted the oceans’ global ecosystem – possibly irreparably.”

    The legal profession would call this statement “conclusory.” Can you back this allegation up with verifiable facts? How can you possibly know that 75% of the world’s fish population has been decimated, or the rest of your statement? How was that 75% number calculated? Why not 78% or 69% ? And to decimate means to reduce by 10%, not 75%.

    What happens when you make statements like yours above that have a high probability of being false or nonprovable, is that the rest of your argument becomes suspect as well.

    1. Regenexx Team Post author

      Bob,
      Well stated.

  5. Tim

    Hi CB, could you recommend me what kind of fat & protein (sources) we have to get enough for healthy life:)? Recently I’ve read that omega-3 is the most beneficial & omega-6 to protect omega-3 (I guess from oxidation?).
    I take krill oil 1.0 gr. w/CoQ10 100 mg, B12 & Folic Acid (brand-Daily Nutra) & organic flex seed oil 1.0 gr. The tastes seems are not rancid (unfortunately I don’t have the gas chromatography to check the purity level). I avoid fish & meat & trying to be vegetarian.
    You say waters are poisoned then what about other food (even organic) & supplement production & consumption?
    How we can avoid poisoned waters?
    And just curios how some ocean turtles survive in so much poisoned environment & live over 150 years (genes?)?
    Thanks

    1. Regenexx Team Post author

      Tim,
      This link will take you to many articles on Fish Oil, Omega 3’s, what brands of Fish Oil are reputable, what types and brands to avoid, contains many studies, and answer many of your questions: http://www.regenexx.com/?s=fish+oil etc. There will always be many opinions on every issue, but if we stick with actual studies and not special interest groups, we get a more balanced and factual view of things.

  6. Rich H

    I went out on a chartered fishing boat recently and we caught lots of fish in Lake Ontario. Are intentions were to consume most of our catch in the weeks to come, but we were concerned and asked the captain about mercury in the fish. He quickly replied that the mercury was in the organs of the fish and not the meat per se. So when you fillet a fish properly, as he was doing right on the boat, the organs and mercury go back into the lake. If this is true, then I don’t know what the problem would be in the first place.

    1. Regenexx Team Post author

      Rich,
      The Charter Boat captain appears to have been misinformed. While the concentration of Mercury would be higher in the organs, it is not true that it is not also found in the flesh.

Chris Centeno, MD

Regenexx Founder

Chris Centeno, MD is a specialist in regenerative medicine and the new field of Interventional Orthopedics. Centeno pioneered orthopedic stem cell procedures in 2005 and is responsible for a large amount of the published research on stem cell use for orthopedic applications.
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