Mercury Rising - Are You at Risk?

Sometimes the truth can be hard to come by in today's world of health claims, magic pills, and wonder diets. So what about mercury levels in fish? Is it all hype? In fact, it is not. Nearly all fish contain mercury, which is a naturally occurring element found in air, water, and food. Most of the mercury we come into contact with is from food (particularly fish). Fish contain a type of mercury called methylmercury, an organic form, which is also the most dangerous and cannot be removed by cooking or cleaning the fish. Methylmercury in fish comes from sediment on the ocean floor. The fish absorb the methylmercury through their gills as they swim through streams and oceans. Some fish contain more mercury than others, and factors such as the type of fish, size, location, habitat, diet and age all affect the mercury levels. The effects of methylmercury toxicity can include depression and blurred vision. In fetuses and young children the effects are even more severe, such as decreased attention span, language capabilities, and coordination.

Does this mean that you should avoid fish altogether? Of course not! Fish can be an important part of a healthy diet. It contains high quality protein, is naturally low in saturated fat and calories, and contains omega-3 fatty acids. Studies have shown that a well balanced diet including fish can promote heart health as well. With this being said, some types of fish consumption should still be limited. Larger fish contain the most mercury. This is because they are higher in the food chain, and therefore consume the smaller fish, which contain methylmercury. The larger the fish and the longer it has lived, the more mercury it collects. The FDA (United States' Food and Drug Administration) tests and regulates the fish market. The FDA's current limit for methylmercury is 1 ppm per fish. Any fish containing a higher level of mercury is not permitted to be sold for human consumption. Due to limitations in supervision, the FDA recommends that larger species of fish, such as shark, swordfish, yellowfin tuna,and bluefin tuna, be consumed infrequently due to their higher mercury levels. The EPA (Environmental Protection Agency) also sets a recommended safe 'dose' of mercury exposure for each state and water region.

What does this mean to you the consumer? Well, if you are eating a variety of fish species without consuming in excess you are probably not at risk. The effects of methylmercury poisoning are more likely in the at-risk population, which includes women who are pregnant or nursing, young children, and those with impaired kidney function or a highly sensitive immune response to metals. An excess amount of fish consists of more than 7 ounces per week (a serving size is between 3 to 6 ounces) of the high mercury containing fish (i.e. shark, swordfish). For fish with lower mercury levels, 14 ounces a week is considered tolerable. The recommendations are different for women who are pregnant or plan on becoming pregnant. The suggestion is to completely avoid shark, swordfish, king mackerel, and tilefish. It is acceptable for pregnant women to consume a variety of other types of fish (up to 12 ounces a week), but canned albacore tuna should be limited to 6 ounces a week. Below is a guide that helps break down the types of fish and their recommendation levels.

Fish to be avoided by women who are/may be pregnant or nursing, and young children:
  • Shark
  • Swordfish
  • King Mackerel
  • Tilefish (a.k.a. golden bass, golden snapper)
Slightly lower in mercury but still to be limited:
  • Tuna steak (also used in sushi and sashimi)
  • Canned Albacore white tuna
Fish to be eaten in limited quantities by women who are/may be pregnant or nursing, and young children:
  • Blue mussel
  • Canned light tuna
  • Channel catfish (wild)
  • Cod
  • Eastern Oyster
  • Great Lakes salmon
  • Gulf Coast blue crab
  • Gulf Coast oysters
  • Haddock
  • Halibut
  • Lake whitefish
  • Largemouth bass
  • Mahi mahi
  • Marlin
  • Pike
  • Pollack
  • Sea bass
  • White croaker
  • Walleye
Fish lowest in methylmercury:
  • Catfish (farmed)
  • King crab
  • Fish sticks
  • Flounder (summer)
  • Salmon (wild Pacific)
  • Sardines
  • Scallops
  • Shrimp
  • Tilapia
  • Trout (farmed)

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