The Best Types of Fish to Avoid Mercury

Fish and Mercury
Fish and Mercury. Charlie Schuck / Getty Images

We know that eating fish is good for you. In fact, fish may be the ultimate anti-aging superfood, but eating the wrong kinds of fish too often can raise the level of mercury in your body. This is especially dangerous for pregnant and breastfeeding women because fetuses and newborns are very sensitive to mercury. Find out the best fish to eat and in what amounts.

Why Eat Fish?

Fish are a great source of protein.

They contain healthy fats that will reduce your cholesterol and improve your health. Fish also contain omega-3 fatty acids that help keep your heart healthy and may even improve your mood. Fish have been shown to be an important diet of many long-lived peoples around the world.

Mercury Concerns With Fish

All fish contain trace amounts of mercury. For most people, the small amounts in fish do not pose a health problem. Some fish, however, contain high amounts of mercury—enough to damage a fetus or newborn. That is why pregnant and nursing mothers must be very careful about the amounts and types of fish they eat. Young children should also avoid eating fish high in mercury. According to the FDA, pregnant women and small children (under 6) should not eat more than 2 servings of fish each week—and should only eat those fish with low mercury content (see below).

Mercury levels can build in adults too—eventually becoming harmful to health.

High mercury levels can cause permanent damage to the kidneys and brain. Mercury is naturally eliminated from your body but it can take several months for it to pass through. For that reason, women who are planning to become pregnant may want to begin to avoid fish that are higher in mercury before they become pregnant.

How Does Mercury Get Into Fish?

The mercury found in fish is methylmercury. First, mercury is released into the air and then settles onto the land and into the water. Bacteria and other microorganisms convert the mercury into methylmercury. Then, fish and shellfish in the water begin to absorb it. Fish that eat other fish and who live longer have higher levels of methylmercury.

Effects of Methylmercury on Humans

Methylmercury is toxic to the central nervous system—the brain and spinal cord. It causes irreversible damage. The brains of unborn babies and infants are especially susceptible. How much damage is done depends on how much you are exposed to the chemical. The effects of methylmercury poisoning include cerebral palsy, blindness, deafness, impaired mental functioning, impaired lung function, growth problems, and having a small head.

Which Fish Have the Most Mercury?

Large fish have more mercury for the simple reason that big fish usually live longer. They have more time to build up higher levels of mercury in their bodies. The Environmental Protection Agency (EPA) recommends checking local advisories for the mercury content of fish caught in your area using this website. See the lists below for general mercury levels of many common types of fish and how much of each type to eat (according to the National Resource Defense Council)

Fish and Shellfish Lowest in Mercury

Eat 2-3 servings a week of the following fish (pregnant women and small children should not eat more than 12 ounces or 2 servings):

  • Anchovies
  • Catfish
  • Clam
  • Crab
  • Crawfish
  • Croaker (Atlantic)
  • Flounder
  • Haddock
  • Hake
  • Herring
  • Mackerel (North Atlantic, Chub)
  • Mullet
  • Oyster
  • Perch (The FDA lists this on the low list, but the NDRC lists it as moderate or high)
  • Pollock
  • Salmon
  • Sardine
  • Scallop
  • Shrimp
  • Sole
  • Squid
  • Tilapia
  • Trout
  • Whitefish

Fish With Modest Amounts of Mercury

Eat six servings or fewer per month (pregnant women and small children should avoid these):

  • Bass (Saltwater, Stiped, Black)
  • Buffalofish
  • Carp
  • Cod (Alaskan)
  • Halibut
  • Lobster
  • Mahi Mahi
  • Monkfish
  • Perch (freshwater)
  • Snapper
  • Skate
  • Tilefish (Atlantic)
  • Tuna (canned chunk light)

Fish High in Mercury

Eat three servings or less per month (pregnant women and small children should avoid these):

  • Bluefish
  • Grouper
  • Sea Bass (Chilean)
  • Mackerel (Spanish, Gulf)
  • Croaker (White, Pacific)
  • Sablefish
  • Perch (ocean)
  • Tuna (canned albacore, yellowfin)

Fish Highest in Mercury

The FDA lists these choices to avoid eating:

  • King mackerel
  • Marlin
  • Orange Roughy
  • Shark
  • Swordfish
  • Tilefish (from the Gulf of Mexico)
  • Tuna (Bigeye, Ahi)
  • Bluefish and grouper: The National Resources Defense Council adds these to the list of those to avoid.

A Word From Verywell

Fish can be part of a healthy diet, but it is wise to choose fish that will be lower in mercury. If you or members of your family are at a stage of life where exposure to mercury should be kept to a minimum, be sure to follow the FDA recommendations to only choose low-mercury fish and have only two servings per week.

Sources:

Center for Food Safety and Applied Nutrition. Metals - Eating Fish: What Pregnant Women and Parents Should Know. U S Food and Drug Administration Home Page. https://www.fda.gov/Food/FoodborneIllnessContaminants/Metals/ucm393070.htm.

Greenfield, N. The Smart Seafood Buying Guide. National Resource Defense Council. https://www.nrdc.org/stories/smart-seafood-buying-guide.

Mercury Levels in Commercial Fish and Shellfish. Food and Drug Administration (FDA). https://www.fda.gov/food/foodborneillnesscontaminants/metals/ucm115644.htm.

Methylmercury poisoning. MedlinePlus Medical Encyclopedia. https://medlineplus.gov/ency/article/001651.htm.

Public Health Statement for Mercury. Centers for Disease Control and Prevention. https://www.atsdr.cdc.gov/phs/phs.asp?id=112&tid=24. Published January 21, 2015.​​

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