Mercury is a natural part of the Earth's environment, and its presence is increased by human activity. Mercury is in the air, water, and soil of the planet. Fish absorb mercury in the water, and when you eat it, you absorb it, too.
Eating seafood is promoted as part of a healthy diet. Seafood contains an abundance of omega-3 fatty acids, high-quality protein, and many nutrients. And it is low in saturated fat.
These all are positive benefits, and a moderate amount of seafood is a healthy addition to the diet.
But nearly all fish contain at least a trace amount of mercury, and the concern over this issue hovers over this advice. The risk of mercury poisoning is real if you eat a lot of fish, especially fish that has a high concentration of mercury.
Women who may become pregnant, are pregnant or nursing, babies, and young children are especially at risk because mercury is toxic to a child's developing brain and nervous system, say the Food and Drug Administration and the Environmental Protection Agency. These groups especially should avoid the fish on the top level of this list with the highest amounts of mercury and limit their consumption of fish on the other levels, the FDA and the EPA advise. It's wise for any woman of child-bearing age, from age 16 to 49, to also avoid eating fish that has the highest mercury levels, the FDA says.
The FDA advises that women at high risk can eat two to three servings a week of seafood with low mercury levels and one serving per week of fish with mid-range levels. It says children over age 2 can have one or two servings of seafood a week. Moderation and mindfulness are key.
Everyone else should try not to eat more than one or two meals per month of fish and seafood with the highest levels of mercury; that means go easy on the bigeye tuna.
These levels are designated by the FDA.
Fish With the Highest Levels of Mercury
- King mackerel
- Tilefish (Gulf of Mexico)
- Orange roughy
- Bigeye tuna
Fish and Seafood With Mid-Range Mercury Levels
- Tuna (all varieties except bigeye and skipjack)
- Spanish mackerel
- Chilean Seabass
- Weakfish (sea trout)
- Striped bass
- Tilefish (Atlantic Ocean)
- Mahi Mahi
- White and Pacific croaker
Fish and Seafood With Low Mercury Levels
- Freshwater perch
- Canned light tuna (skipjack)
- American and spiny lobster
- Boston or chub mackerel
- American shad
- Flounder, fluke, plaice, sand dabs