Toxic Thursdays-Mercury in Fish

29 Dec

Poison in our Seafood?


If this is the first Toxic Thursday post you have read, check out the posts on shampoo, lotions. and body wash.  Each Thursday, I highlight a potential source of toxins in our everyday lives, explain what health risks the potential toxins have been linked to and suggest healthier, safer alternatives.  Today we are going to talk about mercury levels in fish.

What is Mercury?

Mercury is a naturally occurring chemical element.  Most of the mercury that ends up in the water is from coal-burning power plants and chlorine production plants (source).  The largest source of mercury contamination in the US is from coal-fueled power plants (source).

The dangerous form of mercury is methylmercury.

Methylmercury is formed when mercury is acted upon by anaerobic organisms that live in aquatic areas such as lakes, rivers and the ocean (source).

Why is Methylmercury in Our Fish?

Mercury and methylmercury are present in very small concentrations in water sources.  Methylmercury is absorbed by algae which is at the bottom of the food chain.   This algae is eaten by small fish which are then eaten by larger fish.  Fish absorb the methylmercury but do not excrete it well (source).  Thus, it accumulates in the organs and muscles of fish which are then eaten by larger fish and humans  (source).


What are Methylmercury’s Health Risks?

Mercury cannot be eliminated by cooking (source).  When we eat methylmercury in our food, more than 95% of it is absorbed by the gastrointestinal tract.  It is  transported to the blood and is distributed to all organs. It takes 30–40 hours for methylmercury  to be completely distributed throughout the body.  It then can cross the blood-brain barrier and builds up in the brain.  In the brain, it  can damage the central nervous system (source).  Methylmercury has a half-life in human blood of about 50 days which means it lasts for a very long time in our body (source).

Methylmercury has been linked to:

  • Increased risk of heart attacks (source) (source) (source) and increased risk of death from heart disease.  This is likely due to the promotion of lipid peroxidation by mercury which encourages atherosclerosis(source)
  • Increasing systemic inflammation (source)
  • Increased heart rate and blood pressure (source)
  • Negatively impacting the immune system (source)

It is still undecided if the high mercury content in fish diminishes the cardioprotective effect of fish (source) (source)

Who is Especially at Risk?

Although we should all avoid mercury exposure, pregnant women and children need to be most careful.  Methylmercuy can easily cross the placenta and levels in umbilical cord blood can be 1.7 times higher than the mother’s blood levels (source).

Babies who were exposed to mercury in the womb have shown to experience a loss of IQ and demonstrate decreased performance on tests examining memory, attention, language, and spatial cognition. (source)

How Can We Limit Exposure to Mercury?

The best way to limit your exposure to mercury is to choose fish that are low on the food chain.


Here is a great link listing the mercury levels in different fish and shellfish.


Did you know all the different health risks of mercury?  How do you limit your mercury exposure?


7 Responses to “Toxic Thursdays-Mercury in Fish”

  1. Corinne @ RI Nutrition Housecalls December 31, 2011 at 2:42 am #

    I don’t eat fish or seafood (mainly for ethical reasons) so not getting mercury from those sources is a bonus for me. With all the health benefits you hear about from fish, especially the omega-3’s, it makes you wonder if the trade off with all the contaminants is worth it. The one source of mercury that really scares me, and I know this is controversial, is from amalgam dental fillings. That could be your next topic!

    • naturallyhealthyandgorgeous December 31, 2011 at 12:45 pm #

      I agree with you. I try to limit my fish intake because it’s a little scary. Thanks for the suggestion for the next post! 🙂

  2. Lisa @ Healthful Sense December 31, 2011 at 2:15 pm #

    Glad to see tilapia in the low level section! That is the only fish that my boys will eat…
    I look forward to your take on mercury in dental fillings… dentists tell you they’re safe but it’s always helpful to see what the research says!

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  1. Toxic Thursday-Food Preservatives « naturallyhealthyandgorgeous - January 5, 2012

    […] Thursday post you have read, check out the posts on shampoo, lotions, body wash and mercury levels in fish.  Each Thursday, I highlight a potential source of toxins in our everyday lives, explain what […]

  2. Toxic Thursdays-Toxins in Water « naturallyhealthyandgorgeous - January 12, 2012

    […] first Toxic Thursday post you have read, check out the posts on shampoo, lotions, body wash, mercury levels in fish and food preservatives.  Each Thursday, I highlight a potential source of toxins in our everyday […]

  3. Benefits of Omega-3 Fatty Acids and DHA « naturallyhealthyandgorgeous - February 23, 2012

    […] water fish such as mackerel, salmon and sardines (as mentioned before, be careful to choose fish with low mercury levels or a supplement made from fish with low mercury […]

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