Potential effects include impaired cognitive development and difficulties with attention, memory, and other neurological functions.
This is why marlin is included among the fish that pregnant women and young children should avoid under FDA guidance.
Does marlin provide nutritional benefits?
Yes.
Marlin contains protein and other nutrients found in fish.
However, the presence of beneficial nutrients does not cancel out the potential risk associated with high mercury concentrations.
A healthier strategy is to choose seafood that provides similar nutritional benefits with lower mercury levels.
6. Orange Roughy: A Long-Lived Deep-Sea Fish That Can Accumulate Mercury
Orange roughy is a deep-sea fish that may appear less familiar than tuna, shark, or swordfish.
It has a distinctive orange color and is sometimes sold as a mild-tasting white fish.
Its relatively firm flesh makes it suitable for baking, grilling, and other cooking methods.
However, orange roughy is classified as a high-mercury fish in FDA guidance.
One important reason is its unusual life history.
Why does orange roughy deserve special attention?
Orange roughy are long-lived deep-sea fish.
Some individuals can survive for well over a century.
Because they live for such a long time, they may accumulate mercury over many years.
Their slow growth and late maturity also make them vulnerable to overfishing.
This creates two separate concerns for consumers:
First, their potential mercury content.
Second, the sustainability of harvesting a slow-growing species.
The mercury issue is particularly relevant to pregnant women and children.
Why is a long lifespan important?
Mercury does not disappear immediately after entering a fish's body.
Methylmercury binds to proteins within tissues and is eliminated relatively slowly.
In long-lived fish, repeated exposure over many years can result in significant accumulation.
A large, older fish may therefore contain more mercury than a younger fish of the same species.
The exact amount varies, but the general relationship between age, size, and mercury accumulation is an important feature of many predatory fish.
Should consumers avoid orange roughy?
People following FDA pregnancy and childhood seafood guidance should avoid orange roughy.
Other consumers may wish to choose more sustainable and lower-mercury alternatives.
Cod, haddock, pollock, and certain other white fish can provide similar culinary versatility while generally containing lower mercury concentrations.
7. Why Mercury Is Particularly Dangerous for Pregnant Women and Children
Mercury exposure does not affect every person in exactly the same way.
The amount consumed, duration of exposure, chemical form, and individual susceptibility all influence the risk.
However, pregnancy and early childhood are especially important periods because the nervous system is still developing.
During pregnancy
Methylmercury can cross the placenta.
This means that a pregnant woman may expose her developing baby even if she does not experience obvious symptoms herself.
The developing fetal brain is particularly sensitive to toxic substances.
Excessive exposure may interfere with neurological development.
Possible consequences include problems with:
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Learning ability.
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Memory.
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Attention.
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Language development.
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Fine motor coordination.
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Visual and spatial skills.
The effects can be long-lasting.
This is why seafood recommendations for pregnant women focus on both the benefits of fish and the need to avoid high-mercury species.
During infancy and childhood
Children's brains and nervous systems continue developing after birth.
Their bodies are also smaller, meaning that a given amount of mercury exposure can represent a greater dose relative to body weight.
Parents should therefore pay attention to the species and serving sizes of fish offered to children.
The goal should not be to eliminate seafood from children's diets.
Fish can provide important nutrients, including omega-3 fatty acids, iodine, selenium, vitamin D, and protein.
Instead, parents should select lower-mercury species and follow age-appropriate serving recommendations.
What about adults?
Adults are generally less vulnerable to the developmental effects associated with prenatal exposure.
Nevertheless, excessive methylmercury exposure can still affect the nervous system.
Symptoms of significant mercury poisoning may include numbness, tingling, difficulty walking, muscle weakness, and sensory disturbances.
People who consume large quantities of fish from the same source over extended periods may benefit from discussing their exposure with a healthcare professional.
8. The Difference Between Mercury and Methylmercury
Understanding mercury exposure requires distinguishing between different chemical forms of mercury.
Mercury exists in several forms, including elemental mercury, inorganic mercury compounds, and organic mercury compounds.
Methylmercury is an organic form that can accumulate in fish and other aquatic organisms.
It is particularly important in seafood safety because it is readily absorbed through the digestive system.
It can also cross the blood-brain barrier and placenta.
This makes it especially relevant to neurological health.
The term mercury poisoning is often used broadly, but the health effects depend on the specific form of mercury and the exposure route.
For seafood consumers, methylmercury is the primary concern.
Why can't consumers detect it?
Methylmercury does not give fish a distinctive smell or taste.
A fish containing high mercury concentrations may look completely normal.
It may have clear eyes, firm flesh, and a fresh smell.
It may also taste delicious.
This means that traditional methods of judging freshness cannot determine mercury safety.
Consumers must rely on species identification, reliable sourcing, and established seafood advisories.
9. Six Lower-Mercury Fish Choices That Families Can Consider
The good news is that people do not need to stop eating fish.
There are many seafood options that provide valuable nutrients while generally containing lower mercury concentrations.
The FDA's consumer guidance identifies several fish as Best Choices.
These include:
1. Salmon
Salmon is one of the most popular choices for people interested in heart-healthy eating.
It provides high-quality protein, vitamin D, vitamin B12, and omega-3 fatty acids.
It can be baked, grilled, steamed, or cooked in a variety of other ways.
Salmon is generally a low-mercury seafood choice.
2. Sardines
Sardines are small oily fish that provide omega-3 fatty acids, protein, calcium when eaten with their soft bones, and vitamin B12.
Because they are relatively small and occupy a lower position in the food chain, they generally contain less mercury than large predatory fish.