Mercury in Seafood


“I used to be a vegetarian, but then I started eating fish because of its health benefits. Now everyone is saying fish is bad for you because it is high in mercury. If this is true, which fish should I avoid and which fish do you recommend?” — Carol A.

Your question is quite timely. Unfortunately, the health benefits of not all, but many, fish are countered by contamination. What I am referring to is the problem we have with mercury entering streams, rivers, lakes, and oceans. When mercury enters these bodies of water the bacteria convert it to an organic form called methylmercury — the form that is dangerous to humans.

While methylmercury is a health concern for all of us, the risks are greater in children and women who are pregnant or planning to become pregnant. Infants exposed to mercury before birth may exhibit problems with mental development and coordination. The neurological hardships that may result are similar to cerebral palsy. For children and adults, the symptoms of high mercury levels can include numbness, burning or tingling of the extremities (lips, fingers, toes), fatigue, weakness, irritability, loss of memory and coordination, and changes in hearing and blurred vision.

The cause

Before you run out and start boycotting fish, have you ever wondered where mercury comes from? Methyl mercury is simply the symptom of a superior cause. The mercury in fish is primarily caused by emissions from coal-fired power plants, waste incinerators (burning of garbage), and certain factories and mining operations. According to an Environmental Defense Report, the top 10 mercury hot spots are Indiana, Michigan, Maryland, Florida, Illinois, South Carolina, North Carolina, Pennsylvania, Texas and Tennessee.

While coastal fish are often high in mercury, freshwater fish are more likely to be contaminated than ocean fish. The reason for this is simple: Wherever you have an industry that is near bodies of water, the fish in that area are more likely to be contaminated.

The solution

The problem of mercury-contaminated fish is widespread. However, there are things you can do. For one, you can choose to avoid fish high in mercury. Conceptually, methylmercury biomagnifies the food chain. What this means is that when small fish with low mercury levels get eaten by bigger fish, the amount of mercury biomagnifies. For this reason, long-lived fish and top-level predators like swordfish and sharks often have the highest mercury levels. Also high on the mercury list are farmed salmon (also called Atlantic salmon) orange roughy, albacore tuna, marlin, king mackerel, tilefish, and bluefish.

To continue enjoying delicious fish and enjoying their health benefits, choose wild Alaskan salmon, which is relatively toxin-free and is a great source of omega-3 fatty acids. Also, other fish that are lowest in mercury levels include sardines, herring, and black cod (sablefish).

Keeping in the know

Because of the limited space in my column, I am not able to provide you with a broader spectrum of information on this important concern. For more information, see my Web site,; e-mails are welcome at

Robert Ferguson is a nutritionist, researcher, best-selling author, speaker, host, NAACP nominee, creator of the Diet Free Life methodology, and Chief Nutrition Officer at iCoura Health, Inc., who serves on the Presidential Task Force on Obesity for the National Medical Association. E-mail him at, or visit his Web site at





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