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Heart Smart Living

Cardiologist, author, and heart health expert Dr. Sarah Samaan offers advice on how to live a heart smart life.

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Fish, Mercury, and Your Heart

By Sarah Samaan, MD, FACC | Published Mar 24, 2011

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Mercury Food Chain, CC BY 3.0

Fish is an excellent source of lean protein, and the best way to get heart healthy omega-3 fats into our diet. It’s no wonder that doctors and dieticians recommend seafood to our patients. Unfortunately, pollution from mercury and other toxins threaten the safety of our seas, and may even cause harm to our hearts.

Most mercury in our environment comes from coal burning plants, with the U.S. alone responsible for 48 tons of mercury pollution each year. Tiny algae and plankton take the mercury into their bodies, and are in turn eaten by small fish, which are eaten by larger fish, until eventually the mercury becomes concentrated in the body tissues of many of the fish and other seafood that we eat.

Mercury is more than just a pollutant. It can have serious ramifications for our heart and brain health. It may work against the antioxidants that help to protect our hearts and brains from harm, and may even increase the risk for dangerous blood clots. People with very high levels of mercury in their blood stream have twice the risk for heart attacks and strokes as those who have little or no detectable mercury.

In children and in the developing fetus, mercury can interfere with normal brain development, and can cause permanent damage. That is why the Institute of Medicine recommends that pregnant women, those considering pregnancy, and children eat only six to 12 ounces of seafood each week. Fortunately, adult bodies can usually eliminate mercury over time without long term harm, as long as levels are not allowed to build up indefinitely.

Fish that are especially high in mercury include tilefish (also known as golden bass or golden snapper), swordfish, king mackerel, and shark. To be safe, these fish should be avoided. Tuna is moderately high in mercury, especially white albacore tuna. So are Alaskan cod, halibut and mahi mahi. It’s best to eat these no more than six times each month. Salmon, shrimp, scallops, freshwater trout, and tilapia are considered low mercury fish, and are generally safe. The National Resources Defense Council website lets you download a handy wallet card listing the mercury levels of a wide variety of fish.