Perhaps you’ve come to this site because you’d like to eat more seafood, but are concerned about mercury. The truth is that the real risk for most of us is eating too little fish and ending up with too few omega-3 fats in our diets.
That’s especially true for pregnant women and the developing fetus.
The U.S. government recommends adults eat at least eight ounces of seafood per week. Seafood provides protein, vitamins B12 and D, iron, selenium, zinc, iodine, and those all-important omega-3 fats. Salmon, sardines, crab, and scallops are listed as safe to eat three times a week (Center for Food Safety and Applied Nutrition, 2020).
But here’s the vital part to know: That doesn’t mean you can’t eat more. Mercury exposure has been tied to neurological problems in the developing fetus and in children and animals. However, you’d need to eat a lot of seafood, especially salmon (one of the lowest-mercury kinds of seafood), to run that risk.
In fact, in a 2014 U.S. government report, scientists concluded that a pregnant woman could eat up to 53 pounds of salmon a week without putting her fetus at risk of reduced I.Q. from mercury (Center for Food Safety and Applied Nutrition, 2014). Here’s part of the chart showing risk from salmon and other relatively low-mercury seafood:
In the same report, the benefits of pregnant women eating seafood were startling. Just 10 ounces a week of salmon, roughly three modest servings, could boost her child’s IQ by more than 3 points, on average, by age nine (McGuire et al., 2016). And of course, seafood features abundant brain and heart benefits for those of us who are not pregnant.
You might worry that pollution is increasing, but current levels of mercury in fish remain low enough for the benefits to far outweigh any risks. In a study published this year, a team in Portugal analyzed mercury concentrations in Atlantic mackerel, Atlantic chub mackerel, European anchovy, Atlantic horse mackerel, and European pilchard in the Atlantic off the coast of Europe. They found that the mercury content was far below the European Food Safety Authority and World Health Organization food safety thresholds in all species (Costa, 2020).
One reason to feel safer: Older research assumed that all of the mercury in fish was 100 percent bio-available; that is, capable of circulating in your blood and tissues in a way that could harm you. The new quest is to determine bio-availability, which varies widely, but is rarely 100 percent, and usually much lower (Bradley et al., 2020).
How much is too much?
Suppose you become inspired to eat seafood every day. Will mercury (or other toxins) hurt you? The American journalist Paul Greenberg actually spent a year eating seafood at every meal, in every form he could think of, including spaghetti and fish-balls (Greenberg, 2019).
His omega-3 levels rose. “I had around 11 percent omega-3 levels in my blood — most Americans are below 5 percent. A finding above 8 percent is desirable. Somebody said to me that I had the blood of a Sicilian fisherman circa the 1890s,” he told a reporter for the Today Show.
His mercury levels also rose, but with no apparent bad effects. When he returned to eating two to three portions of seafood a week, those mercury levels fell again. Although mercury can increase your risk of high blood pressure in high doses, in a large meta-analysis Americans generally had mercury exposure that was too low to produce this effect (Hu et al., 2018). Greenberg said his blood pressure didn’t budge during his year-long binge.
What about other toxins?
When it comes to risks from other toxins, including polychlorinated biphenyls (PCBs), dioxins, and pesticide residues, seafood once again appears vindicated. The vast majority of the PCBs and dioxins in the U.S. food supply come from non-seafood sources, including meats, dairy, eggs, and vegetables (Harvard T H Chan School of Public Health, 2019).
In short, Americans don’t need to worry that eating common varieties of fish or shellfish in generous amounts will harm them. They would be better advised to eat these regularly for the many advantages that this nutrient-rich food provides – especially the fatty acids DHA and EPA, which are essential for brain and heart health, and difficult to get from other food sources. This is especially true for pregnant women, who need abundant DHA and EPA to supply the developing fetus’ brain with the building blocks it needs to achieve its I.Q. potential.
If mercury in seafood remains a concern for you, stay away from large predator fish such as swordfish, king mackerel, fresh big-eye tuna, shark, and orange roughy, where mercury can tend to bioaccumulate. Gorge instead on cod, crab, flounder, haddock, oysters, salmon, sardines, scallops, and shrimp (Center for Food Safety and Applied Nutrition, 2020), where mercury concentrations are so low that even the most voracious fish-eating pregnant woman can’t consume enough to cause harm.
Wild Alaskan salmon in particular is an excellent choice. The Alaska Department of Environmental Conservation, which samples thousands of fish, has determined “All species of Alaska wild salmon have very low levels of mercury” (Fish Facts and Consumption Guidelines). Yet salmon is among the richest sources of vital omega-3 fatty acids, a classic win-win.
Bradley MA, Barst BD, Basu N. A Review of Mercury Bioavailability in Humans and Fish. International journal of environmental research and public health. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5334723/. Published February 10, 2017. Accessed September 18, 2020.
Center for Food Safety and Applied Nutrition. Advice About Eating Fish. U.S. Food and Drug Administration. https://www.fda.gov/food/consumers/advice-about-eating-fish. Accessed September 19, 2020.
Center for Food Safety and Applied Nutrition. Peer Review on Quantitative Assessment on Net Effects from Eating Fish. U.S. Food and Drug Administration. https://www.fda.gov/food/metals-and-your-food/peer-review-report-quantitative-assessment-net-effects-eating-commercial-fish-fetal-neurodevelopment. Published 2014.
Costa F, Coelho JP, Baptista J, Martinho F, Pereira ME, Pardal MA. Mercury accumulation in fish species along the Portuguese coast: Are there potential risks to human health?. Mar Pollut Bull. https://pubmed.ncbi.nlm.nih.gov/31780086/ Published January, 2020.
Fish: Friend or Foe? Harvard T.H. Chan School of Public Health. https://www.hsph.harvard.edu/nutritionsource/fish/. Published May 22, 2019.
Fish Facts and Consumption Guidelines. (n.d.). Retrieved September 21, 2020, from http://dhss.alaska.gov/dph/Epi/eph/Pages/fish/default.aspx
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Institute of Medicine. Seafood Choices: Balancing Benefits and Risks. Washington, DC: The National Academies Press. https://www.nap.edu/catalog/11762/seafood-choices-balancing-benefits-and-risks Published 2007.
McGuire J, Kaplan J, Lapolla J, Kleiner R. The 2014 FDA assessment of commercial fish: practical considerations for improved dietary guidance. Nutrition journal. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4942920/. Published July 13, 2016.
Minamata Disease. "Sustainability" Boston University. https://www.bu.edu/sustainability/minamata-disease/. Accessed September 19, 2020.
TodayShow. What happened when I ate fish at every meal for a year. TODAY.com. https://www.today.com/health/fish-oil-omega-3-supplements-eating-fish-every-day-healthy-t139838. Published April 18, 2019.
Ye BJ, Kim BG, Jeon MJ, et al. Evaluation of mercury exposure level, clinical diagnosis and treatment for mercury intoxication. Ann Occup Environ Med. 2016;28:5. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4724159/ Published January 22, 2016.