Methylmercury is toxic to the human body, specifically the brain, kidneys, liver, heart, and nervous system. While mercury itself is a naturally occurring element, human industrial activity--coal-fired electricity generation, for example--pollutes the air and then finds its way into lakes, streams, and the ocean. Fish feed on other fish that are contaminated with mercury, that’s why mercury levels in large fish tend to be higher. This guide uses data from NRDC, EWG, and EPA.
People who aren't aware of mercury levels in fish and are exposed to too much, can suffer from a wide array of symptoms including sleep disturbance, headaches, fatigue, memory and concentration problems, and neuropathy. But mercury is most dangerous to the developing fetus because it can cause lasting problems in infants and children including reduced intelligence, memory and concentration issues, and hyperactivity.
Fresh Salmon (Choose wild salmon because farmed salmon may be contaminated with PCBs and other chemicals.)
Shrimp (Check the fishing method because unsustainable fishing methods, often used to catch shrimp, can cause major environmental damage.)
Moderate Mercury (6 servings or less per month)
Atlantic or Pacific Halibut
Canned Light Tuna
High Mercury (3 servings or less per month)
Spanish or Gulf Mackerel
Sea Bass (overfished)
Albacore Canned Tuna
Yellowfin Tuna (overfished)
Highest Mercury (Avoid. Mostly all of the highest mercury fish are also overfished)
Bigeye or Ahi Tuna
However, while mercury levels in fish are important, Omega 3 fatty acids are also important for the developing fetus and for heart and brain health in adults, it’s important to choose fish that are high in omega 3 fatty acids and low in mercury. It’s not that you can’t eat fish that are low in omegas and low in mercury, but if you’re in search of omegas, here’s how to get your fill.
High In Omega 3 Fatty Acids, Low in Mercury
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Image: Pedro Angelini