Fish may be an 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.

Overview

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 age 6) should not eat more than two servings of fish each week—and should only eat those fish with low mercury content.

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 Fish Get Contaminated

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 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.﻿﻿

Mercury Levels in Fish

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. 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).﻿﻿

The Environmental Protection Agency (EPA) recommends checking local advisories for the mercury content of fish caught in your area using their website.

Low Levels

Herring. Verywell / Alexandra Shytsman

Eat two to three servings a week of the following fish (pregnant women and small children should not eat more than 12 ounces or two 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

Moderate Levels

Halibut. Verywell / Alexandra Shytsman

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

Bass (Saltwater, Striped, Black)

Buffalofish

Carp

Cod (Alaskan)

Halibut

Lobster

Mahi Mahi

Monkfish

Perch (freshwater)

Snapper

Skate

Tilefish (Atlantic)

Tuna (canned chunk light)

High Levels

Mackerel. Verywell / Alexandra Shytsman

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)

Highest Levels

The FDA lists these choices to avoid eating:

Bluefish and grouper: The National Resources Defense Council adds these to the list of those to avoid.

King mackerel

Marlin

Orange Roughy

Shark

Swordfish

Tilefish (from the Gulf of Mexico)

Tuna (Bigeye, Ahi)

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. Explore recipes for fish, including these using seafood from the low-mercury list:

Enjoy this great source of protein and omega-3 fatty acids. In fact, many long-lived peoples around the world have a diet rich in fish and seafood.﻿﻿