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Mercury in Fish: Cause for concern?

Health Benefits and Risks of Eating Fish

Fish is an important part of a balanced diet. It provides essential fatty acids, lean protein, and several vitamins and minerals (zinc, iron, calcium, selenium, iodine, Vitamins A, D, E and B Vitamins).

The types of fats found in fish are referred to as polyunsaturated fatty acids and these are heart healthy fats (unlike the saturated fats found in red meat, butter, and fried foods). By consuming fats, you are also helping your body absorb certain vitamins (A, D, E & K).

Due to all of the health benefits of consuming fish, we obviously do not want to overlook them in our diets. However, some fish are safer than others when it comes to mercury levels and it is important to know how mercury bioaccumulates in our seafood.

Methylmercury in our food - cause for concern

Mercury occurs naturally in our environment and major sources include waste incineration and the burning of fossil fuels. However, 75% of our exposure to methylmercury- a toxic residue of mercury converted by bacteria in the water-comes from consumption of fish. Methylmercury is a neurotoxin which damages the tissue of the central nervous system. This is of particular importance to women of child bearing age due to its deleterious effects to the unborn fetus.

Methylmercury has also been linked to cardiovascular disease which is troubling to many since heart disease patients are encouraged to eat more fish/seafood for the essential omega-3 fatty acids that they possess (heart healthy fats). If you get your blood checked for mercury, anything above 5 micrograms per liter is considered too high.

The process of bioaccumulation: Today, levels of mercury in soil are three times higher than they were before the Industrial Revolution. The real trouble starts when this mercury runs out of the soil and into the water and is converted into methylmurcery by bacteria present in the water. Plankton contaminated with methylmercury are eaten by small fish which get eaten by larger fish. Humans then eat these large fish and the resulting high levels of methylmercury in their tissue. This level can be up to 1 million times higher than the level in the water when it first enters.

*This is a good reason not to eat large, longer-lived fish such as shark, swordfish, king mackerel, golden bass (tilefish), Albacore tuna, marlin, and grouper.

Mindful eating to avoid mercury in Fish

The more fish you eat, the more aware you need to be of the mercury content of your fish and seafood choices.

Responsible Seafood Choices- a list of available wild-caught fish and their sustainability ratings developed by the Blue Ocean Institute.

Mercury in Fish Pocket Guide- go for the green! This guide also denotes fish with high levels of PCB’s and those that are caught using environmentally destructive methods.

Today’s post was written by Kristin Bogdonas, MPH. She is a Certified Health Education Specialist and Nutrition & Wellness Educator covering Mercer, Henry, Rock Island and Stark Counties. She specializes in local foods, seasonal eating, program planning, and food safety/preservation.



Blue Ocean Institute

Virtanen, J.K., Rissanen, T.H., Voutilainen, S., Tuomainen, T.P. (2007). Mercury as a risk factor for cardiovascular diseases. J Nutr Biochem, 18(2), 75-85.

Effect of Marine Omega 3 Fatty Acids on Methylmercury-Induced Toxicity in Fish and Mammalian Cells In Vitro.

Mozaffarian D. Fish intake, contaminants, and human health: Evaluating the risks and the benefits. Cardiology Rounds. 2006 Oct;10(8).