According to Environmental Toxicology and Chemistry over 50% of tested canned tuna (from national brands) exceeded the U.S. Environmental Protection Agency’s (EPA) safety levels.  Learn more about mercury levels and read my recommendations to minimizing mercury in your diet.

Interestingly the FDA found only 5% of the same tested tuna to be over the safety allowance for human consumption.  Clearly the FDA does not have as strict standards as the EPA when it comes to allowable mercury levels. 

The researchers said that “Americans consume about 1 billion pounds of canned tuna a year”, wow!  It is true that some varieties of tuna are lower in mercury such as canned light tongol, but you still have high residues of toxins from the metal can!  Basically fish is the main culprit for exposing people to methylmercury (the organic form) which is why it is important to be aware of the seafood you are choosing. 

The body is capable of dealing with small amounts of mercury and it is normal to find trace amounts in the blood stream.  As long as high-mercury fish are eaten sparingly, you shouldn’t be alarmed.  For those absorbing too much mercury through food, water, environment and injections, you may experience some common symptoms of mercury poisoning (fatigue, headache, memory loss and joint pain/ inflammation).  Mercury toxicity can be very poisonous to the nervous system, has been linked to cancer, and can harm an unborn baby.  If you are concerned about the mercury-levels in your body, the levels can be tested through blood and hair analysis.

Levels of mercury in fish are dependent on 4 main factors:

1. The mercury content in the water
2. Size of the fish
3. A fish’s lifespan
4. Whether or not the fish has gills

Generally, the larger the fish, the higher levels of mercury stored.  A fish that is higher on the food chain tends to eat a large variety of other fish.  That large fish will absorb the smaller fish’s mercury-laden protein (mercury stores in the protein tissue of the fish).  Fish that live longer naturally absorb more mercury during their lifetime.  As they age and grow larger, they are more likely to eat larger fish with higher mercury concentrations.  Lastly, fish with gills are able to circulate clean water through their body and eliminate unhealthy toxins and wastes.  Fish without gills don’t have a built-in filtration system and are more likely to store toxins.

Here are my recommendations…

1. 1.     Be extra cautious with children, pregnant women and nursing moms eating fish, especially albacore tune, high in mercury.
2. 2.     Don’t buy canned albacore tuna because it has higher amounts of mercury compared to light canned tuna which is considered low in mercury.
3. 3.     Avoid these fish which are highest in mercury: Shark, swordfish, marlin, King Mackerel, albacore tuna, barracuda and whales
4. 4.     Consume these fish minimally that have moderate amounts of mercury: Wild Ahi, sea bass, red snapper, trout, grouper
5. 5.     Consume these fish more freely which are the lowest in mercury: Wild salmon, cod, herring, halibut, sardines and catfish

Smaller fish such as mackerel and sardines are extremely low in mercury due to their size.  Most supplement companies who produce fish oils, generally use mackerel and sardines due to their low-mercury levels. 

References:

http://www.epa.gov/waterscience/fish/advice/index.html

Environmental Toxicology and Chemistry

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