Fish provide healthy essential fatty acids and high quality protein, but some species are contaminated with high levels of a dangerous substance called mercury. While almost all fish contain some mercury, certain species have much higher levels than others. Understanding the dangers of mercury in fish and how to avoid getting too much can help ease your mind and allow you to enjoy a delicious seafood dinner without worrying about mercury contamination.
Mercury
Mercury builds up in the environment after being emitted by industrial factories. When it enters water, it becomes methylmercury, which can enter the bodies of fish, where it builds up to potentially dangerous levels. Consumers who eat fish may ingest mercury in their meals and develop health problems related to mercury toxicity. Symptoms of chronic mercury poisoning in adults can include blindness, deafness and an increased risk of heart attack. Infants exposed to methylmercury in the womb or shortly after birth may develop a form of cerebral palsy that is characterized by brain and spinal cord damage.
Fish Types
The fish with the highest levels of mercury is tilefish, with 1.45 parts per million, or ppm. Shark, swordfish and king mackerel all have levels above .70 ppm. Salmon is a healthy fish, low in mercury and high in beneficial omega-3 fatty acids. Fresh or frozen salmon contains 0.014 ppm of methylmercury. Sardines are another good fish choice, with 0.016 pm of mercury and 351 mg of calcium, an important mineral for bone health. Other healthy fish low in mercury include pollock, catfish, canned light tuna, tilapia, anchovies and haddock. The fish used to make fish sticks and fried fish sandwiches tends to be species low in mercury.
Fish Origin
The place where a fish originates may be more important than the type of fish when it comes to mercury levels. For example, Spanish mackerel from the Gulf of Mexico have over twice the amount of mercury than Spanish mackerel from the southern Atlantic ocean.
Considerations
Pregnant women, nursing mothers and small children are particularly vulnerable to the effects of mercury. Women of childbearing age who could become pregnant may also want to stick to low-mercury fish, since the element can build up in the body and remain there for a long time.
Recommendations
The American Heart Association recommends that healthy adults consume at least two 3.5 oz servings of fish per week, but preferentially choose fish having lower levels of mercury. The FDA warns pregnant and breastfeeding women to completely avoid fish with high levels of mercury, including swordfish, shark, tilefish and king mackerel. These women should eat 12 oz or less of fish and seafood per week, preferentially choosing from species with the lowest levels of mercury, such as canned light tuna, salmon, shrimp, oysters, pollock, and catfish.
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