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EWG’s Consumer Guide to Seafood: Frequently Asked Questions
- Why is mercury in fish?
- Why should we eat more fish? Aren’t global fisheries at risk?
- Should I be concerned about other pollutants in seafood?
- How much seafood should I eat?
- I am vegetarian, what should I do to get omega-3 fats?
- Should I take an omega-3 (DHA) supplement?
- How does EWG’s seafood advice differ from the 2014 advisory issued by the FDA and EPA?
Why is mercury in fish?
Industrial mining and coal-fired power plants are the major sources of mercury in the environment. When mercury is emitted into the air, it condenses and falls into waterways and oceans, where bacteria and zooplankton transform it into methyl mercury, an organic compound that is more toxic than elemental mercury and inorganic mercury compounds.
Methyl mercury pollution concentrates in the marine food chain. Mercury concentrations are highest in predatory fish that eat smaller fish. In 2013 the U.S. and 100 other nations signed the Minamata Convention, a global treaty committing signers to reducing mercury emissions. The treaty is a good start, but as ocean temperatures rise because of global warming, mercury accumulation is projected to intensify due to increased metabolic activity in the marine creatures in the lowest tier of the ocean food chain. This increase in mercury could lead to greater concentrations in larger fish and increased risk for seafood consumers.
Why should we eat more fish? Aren’t global fisheries at risk?
Over the past decade the scientific evidence on the health benefits of fish consumption has become more definitive. Federal nutrition guidelines now recommend that all adults and children aim to eat two or three seafood meals per week. If Americans adopted this advice the massive increase in seafood consumption would strain global fisheries. EWG encourages consumers to optimize the benefits of seafood by picking healthy, sustainably produced seafood. The Monterey Bay Aquarium Seafood Watch® website offers extensive details about ecological sustainability of commercial fish and shellfish stocks.
What about other pollutants in seafood?
Decades of industrial activities have polluted fish and shellfish with a variety of toxic chemicals. Fat-accumulating organic molecules like dioxin and PCBs can be found in fatty fish, which are in many cases those with higher concentrations of omega-3 fats. In general the benefits of eating fatty, low-mercury seafood from commercial fisheries outweigh other the harms from other persistent contaminants. However if you eat more than three meals per week, or get species harvested from highly polluted areas the balance could shift. Frequent fish eaters should search EPA’s database of government warning for local waterbodies. In general it is healthiest to eat a variety of species to minimize the risks from elevated levels of pollutants in any particular species.
How much seafood should I eat?
That depends primarily on your health status. If you are pregnant, nursing or have heart disease, you should eat fish and shellfish with some regularity.
EWG recommends that people who enjoy eating seafood aim for one or two meals of sustainable, low-mercury seafood each week. Pregnant women, children and people with heart disease should include species high in omega-3 fatty acids. More than three meals per week may not be beneficial and increases your exposure to other contaminants in seafood. EWG’s EWG’s Good Seafood Guide gives specific recommendations for women who are pregnant or considering pregnancy, parents feeding young children, people with heart disease, sushi or tuna lovers, and people who eat non-commercial fish and shellfish.
EWG’s Seafood Calculator will help you pick the best seafood and give advice tailored to your age, weight and health status.
I am a vegetarian, what should I do to get omega-3 fats?
Vegetarians may miss out on some of the health benefits of omega-3 fatty acids, because they are found primarily in fish and shellfish. If you are pregnant, nursing or considering pregnancy, you should consult with your doctor about the best way to add extra omega-3 your diet. Some nutritional supplements market DHA and EPA extracted from seaweed, and some omega-3 fortified eggs and margarines derive omega-3s from vegetarian sources. If you buy foods that claim to be fortified with omega-3s, check the DHA or ALA content. (No foods are supplemented with EPA.) Keep in mind that nutritional guidelines suggest that women consume an average of 250 milligrams of DHA and EPA daily during pregnancy. Many foods contain far less.
Should I take an omega-3 (DHA) supplement?
There are a variety of omega-3 nutritional supplements that contain DHA and EPA. Most are derived from fish oil. In general, dietary supplements are poorly regulated, so consumers do not have independent verification of the omega-3 content or contaminants in fish oil supplements. Consumer Labs tests of fish oils sold in the U.S. found none with more than 0.01 parts per million mercury; meaning fish oils contained notably less mercury than a single serving of fish1.
The National Center for Complementary and Integrative Health, a branch of NIH reports that eating fish is generally more beneficial than omega-3 supplements, particularly for cardiac health. This may be due to the fact that in addition to omega-3s, seafood has important trace nutrients like iodine, vitamin D, vitamin B12 and selenium. The Office of Dietary Supplements gives a more detailed review of the evidence about beneficial omega-3 fats.
While many studies find a benefit of consuming fish during pregnancy there is less evidence that omega-3 supplements provide a similar benefit.2 One recent meta-analysis found existing evidence did not “support or refute that omega-3 supplementation improves cognitive or visual development.”3 Another concluded the some evidence of lower rates of some allergies in children in the first three years of life, but researchers concluded the overall evidence was “limited” on the ability of omega-3 supplements to lessen risks of allergic diseases.4 Yet at least one expert in seafood and pregnancy recommend omega-3 supplements as a low risk and possibly beneficial supplement during pregnancy.5
Fish liver oils, such as cod liver oil, are not the same as fish oil supplements. Fish liver oils contain high doses of vitamins A and D in addition to omega-3 fatty acids. Both of these vitamins can be toxic in large doses, and excessive vitamin A is particularly harmful during pregnancy and childhood.
EWG recommends that women who are pregnant and anyone at risk for cardiac disease consult their physicians if they do not eat seafood frequently to discuss other ways to add omega-3s to their diets.
How does EWG’s seafood advice differ from the 2014 advisory issued by the FDA and EPA?
EWG’s recommendations are stricter, more comprehensive and more user-friendly than those of the federal agencies.
Our calculator and wallet card aim to steer consumers toward the species that provide the highest amounts of omega-3 fatty acids and least mercury. In contrast the FDA and EPA recommend that pregnant women eat seafood frequently but name only four highest mercury species to avoid. EWG recommends limiting additional high-mercury species. The EWG Seafood Calculator estimates portion size and frequency based on a child or adult’s weight and recommends that pregnant women and children ingest 25 percent less mercury than the current EPA guideline.
The FDA and EPA issued their first Joint Advisory on Seafood in 2004, before the protective role of omega-3 fatty acids in pregnancy was clearly understood. Earlier this year the FDA and EPA proposed to update their joint advisory to recommend that pregnant women eat a minimum of 8 to 12 ounces of fish and seafood per week and to “choose fish lower in mercury” (FDA 2014a). But the draft guidelines do not provide the details that consumers need to select the healthiest species. EWG has urged the agency to provide more specific and protective guidance for consumers.
For example, consumers who read the proposed new seafood guidance by the federal Food and Drug Administration and Environmental Protection Agency will find that the first mention of omega-3 fatty acids is well down on the first page of the agencies’ announcement and does not appear at all on a PDF summary linked to that page, even though omega-3s are a primary reason the government is encouraging people to eat more fish. Consumers who scroll down the announcement page will find a table of commonly eaten fish and their associated omega-3 and mercury levels, but it is very difficult to determine from this table how much of these fish people must eat per week to get the recommended amount of omega-3s and how much they can eat per week without getting too much mercury.
As EWG’s January 2014 report cautioned, not everyone who followed federal government dietary guidelines and eats two or three fish meals per week will achieve the intended health benefits because some people could consume too much mercury, and others, too few omega-3s (EWG 2014). Eight of the 10 most popular seafood species are very low in omega-3s. Other popular choices, like canned albacore tuna, swordfish and some types of sushi, pose a risk of too much mercury if pregnant women or children eat them frequently.
EWG has repeatedly urged the federal government to improve its guidelines for mercury in seafood and to get contaminated species off store shelves. We have stressed that it must provide consumers with clearer and more detailed advice about mercury in seafood and must highlight clearly beneficial choices, or consumers may consume too much mercury and/or too few omega-3s (EWG 2014). Until the government heeds our advice, EWG’s Seafood Calculator is the only online consumer guide that gives health-based seafood recommendations that incorporate both beneficial fatty acids and mercury concerns and that tailor portion size and frequency recommendations based on an individual’s bodyweight and health status.
1 Consumer Lab. 2013. Product Review: Fish Oil and Omega-3 Fatty Acid Supplements Review (including Krill, Algae, and Calamari Oil). Consumer Lab.com, January 3, 2013. https://www.consumerlab.com/reviews/fish_oil_supplements_review/omega3/
Adrian Covaci, et al. 2010. Chapter 20, Anthropogenic and Naturally Produced Contaminants in Fish Oil: Role in Ill Health. In Modern Dietary Fat Intakes in Disease Promotion. Available: http://link.springer.com/chapter/10.1007%2F978-1-60327-571-2_20
2 Cristina Campoy, et al. 2012 Omega 3 fatty acids on child growth, visual acuity and neurodevelopment. British Journal of Nutrtion.107 Suppl 2:S85-106. Available: http://journals.cambridge.org/abstract_S0007114512001493
3 Jacqueline F. Gould. 2013. The effect of maternal omega-3 (n-3) LCPUFA supplementation during pregnancy on early childhood cognitive and visual development: a systematic review and meta-analysis of randomized controlled trials. American Journal of Clinical Nutrition. 97(3):531-44. Available: www.ajcn.nutrition.org/content/early/2013/01/30/ajcn.112.045781.full.pdf
4 Anoja W. Gunaratne. 2015. Maternal prenatal and/or postnatal n-3 long chain polyunsaturated fatty acids (LCPUFA) supplementation for preventing allergies in early childhood. Cochrane Database Systemic Review. 22;7:CD010085. Available: www.onlinelibrary.wiley.com/doi/10.1002/14651858.CD010085.pub2/abstract
5 Emily Oken, et al. 2012. Which Fish Should I Eat? Perspectives Influencing Fish Consumption Choices. Environmental Health Perspectives. 120(6)790-8. Available: www.ncbi.nlm.nih.gov/pmc/articles/PMC3385441/