There are numerous healthy benefits of eating seafood. Fish and shellfish contain high levels of protein and essential nutrients and low levels of saturated fat. “Oily” fish like mackerel, sardines, and wild salmon are a good source of omega-3 fatty acids, which can promote neurological development, and reduce cardiovascular disease and growth of some cancers.
Eating some seafood, however, carries a health risk. Some species of fish contain high levels of polychlorinated biphenyls (PCBs) and/or mercury that are toxic and can cause a range of health problems including cancer, reproductive problems and memory loss. The risk is highest for infants and unborn babies. PCBs are man-made chemicals and were commonly used in paints, lubricants and pesticides; they are no longer manufactured today. Mercury is naturally occurring, although the greatest source today is from coal-burning power plants where it is washed from the sky into rivers and waterways. Both compounds are long-lasting in the environment and bioaccumulate in tissues, particularly organs, skin and fat.
Bioaccumulation causes the concentrations of PCBs and mercury, and thus their toxicity, to increase as you can move up the food chain from small to predatory fish. Large, long-lived fish have also had more time to accumulate these toxins in their tissues. Top predators like sharks, swordfish and some tunas and salmon therefore have the highest concentrations of mercury or PCBs. Considering that canned tuna and salmon are the 2nd and 3rd most commonly eaten seafood in the US, this is a major concern. However, not all tuna and salmon are equally unhealthy. Canned light tuna typically consists of Skipjack Tuna, which is a fast growing, relatively small tuna species; these attributes make it less likely to accumulate much mercury. Wild Alaska Salmon is healthier than Farmed Salmon, because it is largely free of PCBs. Both Skipjack Tuna and Wild Alaska Salmon score highly on BOI ranking system, so consumption is good both for the environment and your health.
To see whether your seafood dinner contains high levels of PCBs or mercury check out BOI seafood pages (http://www.blueocean.org/seafood/seafood-guide) or use FishPhone, our text base querying service. Simply text 30644 with the message FISH and the name of the fish you are curious about.