Mercury in Fish:
The Methyl Mercury Contamination Conundrum

Grilled tuna, succulent sushi, roasted lobster … there’s virtually no end to the delicacies you can find in the water. Disturbing studies, however, have detected high levels of mercury in fish and shellfish. More specifically, fish and shellfish worldwide have elevated levels of methyl mercury—a form of mercury that is linked to several serious health issues when ingested by animals and humans. This, of course, begs the question: is any fish safe to eat?

Generally speaking, the answer is yes, but you have to be careful. It is practically impossible to find mercury-free fish, because regardless of the species, you’ll find at least a small amount of mercury in fish and shellfish. Mercury exists naturally in the environment, and mercury is also released into the atmosphere by coal-burning power plants and other industrial facilities. Eventually, mercury settles in water and on land where microorganisms turn mercury into methyl mercury. Once methyl mercury is absorbed by fish and shellfish, it enters the food supply of both animals and humans.

As you eat seafood over time, mercury in fish and shellfish can accumulate in your body over time and cause mercury toxicity years down the road. According to the Food and Drug Administration (FDA), mercury in fish and shellfish should not exceed 1 part per million, or 1ppm. Cooking does not remove mercury in fish, so the only way to reduce methyl mercury consumption is to monitor the amount and types of fish you eat. Species that are considered high in mercury—close to or more than 1ppm—include king mackerel, swordfish, shark, and tilefish.

Other species tend to have elevated mercury levels, too (up to 0.6 ppm) including grouper, orange roughy, fresh tuna, and frozen tuna. However, these species are not considered problematic as long as you watch your consumption and try to limit it to about three servings a week. If you are concerned about your fish consumption, there are therapies that can help you with heavy metal removal from your body tissues.

It is important to note that, when monitoring the amount of mercury in fish you consume, you should listen for news about mercury in fish because officials may find elevated levels from time to time. Recently, certain species of very large tuna sold as fresh steaks and sushi were found to have methyl mercury levels of more than 1 ppm.

Mercury in fish can be a true health hazard for fetuses and children because their nervous systems are still developing and are very sensitive to methyl mercury. For this reason, babies, children, and women who are pregnant should be especially careful about the types and amounts of fish and shellfish they eat. This warning also applies to women who may one day become pregnant, because mercury in fish can accumulate in the body over time.

Fish and shellfish are full of essential fatty acids and other nutrients that are an important part of a nutritious diet. As long as you don’t have other health issues like allergic reactions, you don’t have to ban fish and shellfish from your life. Simply be aware of mercury in fish, pay attention to news reports, and keep track of the amount you eat.