On EWG web site, it has published a report on seafood choices.  We eat fish or shellfish for the benefits of omega-3s.[1] However, seafood are also high in mercury and other pollutants (i.e., PCBs).[4] Therefore, we need to choose fish based on its omega-3 and mercury levels.  

Tradeoffs

These days we need to pay more attention to what fishes to eat and what not because fishes could be contaminated with toxic compounds such as mercury, lead, PCB, or pesticide.[8]  

While PCBs are present in everything from dairy products to drinking water, the highest levels tend to be found in fish.

While mercury can be found in other foods, such as vegetables, one study found that 78% of participants' mercury intake came from fish and seafood.

Based on a seafood guide published by Monterey Bay Aquarium, fishes are classified into three categories:

• Best Choices

  • Well managed, caught or farmed in environmentally responsible ways.

• Good Alternatives

  • Some concerns with how they are caught or farmed.

• Avoid

  • Overfished, or strong concerns with how they are caught or farmed.

For a full list of recommendations please visit Monterey Bay online or download their application.  If you are pregnant, you should also read Mayo Clinic's guidelines.[5,8]

The NHS recommends that pregnant and breastfeeding women limit their intake of fish species more likely to contain PCBs, as well as other pollutants like dioxins, to two portions per week.

Although mercury can affect the central nervous system at any developmental stage, unfortunate episodes of community-wide poisoning in Japan and Iraq revealed the particular sensitivity of the fetus to the toxic effects from mercury exposure.[10.11]

Depending on your age, weight, and gender, EWG makes the following recommendations on what kinds of seafood to eat or avoid.  Calculation are based on 4 oz. serving size.  Note that sustainability is also considered in EWG's recommendations, which is based on the Seafood Watch from Monterey Bay Aquarium.[2,6]

References

1. California Fish Contaminated with Fukushima Radiation (accessed in 2013)

2. Monterey Bay Aquarium Seafood Watch 2013 (new link)

3. Farm raised vs. wild caught salmon (Dr. Mercola)

4. Farming the Seas (PBS)

5. Pregnancy and fish: What's safe to eat?

6. There Aren’t Plenty of Fish in the Sea

7. Polychlorinated Biphenyls (PCBs) and Their Impacts on Human Health: A Review

   • PCBs are considered potent toxicants capable of producing a wide spectrum of adverse health effects in humans such as skin diseases, enzyme induction, liver toxicity, vitamin A deficiency, endocrine effects, immune system effects, brain dopamine levels deficiency, and genotoxicity. 

8. Is eating fish healthy?

9. Fish consumption, methylmercury and child neurodevelopment

10. Harada M. Minamata disease: methylmercury poisoning in Japan caused by environmental pollution. Crit Rev Toxicol. 1995;25:1–24.

11. Amin-Zaki L, Elhassani S, Majeed MA, et al. Intra-uterine methylmercury poisoning in Iraq. Pediatrics. 1974;54:587–595.