Making Informed Seafood Choices
While seafood is a valuable source of protein and heart-healthy omega-3 fatty acids, not all fish and shellfish are created equal. Several factors influence seafood safety and quality, including the levels of mercury and other pollutants, the risk of foodborne illnesses, and the sustainability of fishing or farming practices. Consumers, particularly those in vulnerable groups like pregnant women, nursing mothers, and young children, must navigate these risks by making informed choices.
The Dangers of High Mercury Levels
Mercury is a neurotoxin that can accumulate in large, predatory fish over their lifespan through a process called bioaccumulation. When consumed by humans, high levels of mercury can damage the brain and nervous system, especially in developing babies. The U.S. FDA and EPA advise certain groups to completely avoid fish with the highest mercury content.
High Mercury Seafood to Avoid:
- Shark: A large, long-living predator at the top of the food chain.
- Swordfish: Another top predator known for its high mercury concentration.
- King Mackerel: A larger mackerel species to be avoided, unlike its smaller, safer relative, the Atlantic mackerel.
- Marlin: Similar to swordfish and shark, marlin contains high levels of mercury.
- Tilefish (Gulf of Mexico): This species, specifically from the Gulf, is flagged for high mercury.
- Bigeye Tuna: Often used in sushi, bigeye tuna has one of the highest mercury levels among tuna species.
- Orange Roughy: A long-lived, slow-reproducing bottom feeder with high mercury levels.
Limiting Exposure to PCBs and Dioxins
Polychlorinated biphenyls (PCBs) and dioxins are industrial chemicals that persist in the environment and accumulate in the fat of fish and other animals. Fatty fish and bottom feeders in contaminated waters often have the highest levels. While many contaminants were banned decades ago, they remain a concern due to their persistence.
High PCB/Dioxin Seafood to Limit or Avoid:
- Farmed Atlantic Salmon: Some studies have shown higher PCB concentrations in farm-raised salmon, though levels vary by source. Always check the origin.
- Wild Striped Bass and Bluefish: These fatty fish, especially when caught in coastal or freshwater areas with advisories, can carry higher levels of PCBs.
- American Eel: Often overharvested and known to have high levels of PCBs and mercury.
- Local Catfish and Carp: If caught in rivers or lakes near industrial areas, these bottom feeders can contain significant contaminants. Checking local advisories is crucial.
The Importance of Sustainability and Avoiding Overfished Species
Choosing seafood responsibly also means considering the health of ocean ecosystems. Overfishing and harmful harvesting practices can decimate populations and damage marine habitats. Organizations like the Marine Stewardship Council (MSC) and Aquaculture Stewardship Council (ASC) provide certifications to help consumers make sustainable choices.
Unsustainable Seafood to Steer Clear of:
- Bluefin Tuna: Severely overfished and often high in mercury.
- Chilean Sea Bass: This species, also known as Patagonian toothfish, was nearly fished to extinction.
- Imported Farmed Shrimp: While US-farmed shrimp can be a good option, many imported versions rely on environmentally destructive farming practices.
- Sharks, Rays, and Skates: These species are often slow-growing and late to reproduce, making them highly vulnerable to overfishing.
Risks Associated with Foodborne Illness
Improperly handled or undercooked seafood can lead to foodborne illness from bacteria, viruses, or toxins. Vulnerable individuals should be particularly cautious. Cooking seafood thoroughly to an internal temperature of 145°F kills most pathogens.
Foodborne Illness Risk Factors:
- Raw Shellfish: Raw oysters, clams, and mussels can contain harmful bacteria like Vibrio and viruses such as Norovirus and Hepatitis A.
- Sushi and Sashimi: Raw fish preparations inherently carry a risk of bacterial or parasitic contamination.
- Scombroid Poisoning: Improperly refrigerated fish high in histamine, such as tuna and mahi-mahi, can cause an allergic-like reaction.
- Ciguatera Poisoning: Toxin accumulation in large reef fish like barracuda and grouper can cause neurological and gastrointestinal symptoms.
Comparison of High-Risk vs. Safer Seafood
| Feature | High-Risk Seafood (Avoid) | Safer Seafood (Choose) |
|---|---|---|
| Mercury Levels | King Mackerel, Shark, Swordfish, Bigeye Tuna | Anchovies, Salmon, Tilapia, Catfish, Canned Light Tuna |
| Contaminants (PCBs) | Fatty fish from contaminated waters, some farmed salmon | Wild Alaskan Salmon, Mussels, Oysters |
| Sustainability | Bluefin Tuna, Chilean Sea Bass, American Eel | U.S. Wild-Caught Shrimp, U.S. Farmed Catfish, Pacific Sardines |
| Foodborne Illness Risk | Raw shellfish, sushi (for vulnerable groups) | Thoroughly cooked seafood from reputable sources |
| Size & Longevity | Large, older, predatory fish | Smaller, younger fish and fast-reproducing shellfish |
A Balanced Perspective: Eating Seafood Responsibly
Avoiding certain seafood is not about abandoning it entirely, but rather about making educated choices. The health benefits of low-mercury and sustainably sourced fish, like omega-3 fatty acids, are well-documented and important for a healthy diet. By being selective, consumers can minimize risks while still enjoying the nutritional advantages. When in doubt about locally caught fish, consulting advisories from local health or environmental agencies is the safest approach. You can find additional guidance on safe seafood consumption from the official FDA website, which offers detailed lists of fish and their mercury levels. By prioritizing smaller, wild-caught, or sustainably farmed options, and being mindful of food safety, you can make healthy and environmentally conscious choices for yourself and your family.
Where to Find More Information
For detailed recommendations on fish consumption, including specific advisories, check the official FDA website: Advice about Eating Fish.
Conclusion
Knowing which seafood should be avoided is a crucial step toward a healthier and more responsible diet. The primary concerns revolve around high mercury levels in large predatory fish, persistent organic pollutants like PCBs in fatty species, and the risks of foodborne illness from improperly handled or raw seafood. Additionally, considering the sustainability of a species helps protect marine ecosystems. While fish offers many health benefits, careful selection and preparation are necessary to mitigate potential risks. By following guidance from health authorities and choosing a variety of low-mercury, sustainably sourced options, you can safely enjoy seafood as part of a balanced diet.
