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Healthy Choices: EWG’s Consumer Guide to Seafood

Public guidelines on which and how much seafood is safe to eat can be downright confusing, causing some people to avoid the nutrient-dense food all together.
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Healthy Choices: EWG’s Consumer Guide to Seafood
(Olesya_sh/Shutterstock)
Zrinka Peters
4/26/2024
Updated:
4/26/2024
0:00

Seafood, which includes fish and shellfish, has earned its reputation as one of the healthiest, brain-and-body-boosting foods for good reason. Seafood contains generous amounts of high-quality protein, various nutrients including omega-3 fatty acids and vitamin B-12, and trace minerals.

However, despite the oft-mentioned advice to eat fish at least twice a week, determining exactly which types are best can be a challenge. Also, recent research has increasingly highlighted the risk of mercury toxicity from seafood. Let’s have a closer look at which types of seafood are the safest and healthiest.

Weighing Benefits to Risk

The substantial amounts of omega-3 fatty acids found in seafood are likely the main driver for why health-minded people incorporate it as part of their regular diet. These important nutrients offer many potential health benefits.

Jessie Anderson, a board-certified specialist in sports dietetics at Top Nutrition Coaching, told The Epoch Times “Omega-3 fatty acids are a type of polyunsaturated (healthy) fat that is most commonly known for its role in boosting heart, metabolic, and cognitive health while improving pain, inflammation, and symptoms of depression. At the cellular level, omega-3 supports the structure of cell membranes. The specific omega-3s involved in promoting these health benefits are eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)—primarily found in oily fish.”

Along with the health and nutritional benefits of seafood, the risk of methylmercury must also be weighed. However, knowing how to best derive the benefits of seafood while also skirting the toxic effects of methylmercury (MeHg) toxicity can be a challenge.

Much of the mercury that finds its way into seafood comes from industrial emissions, especially power plants that burn coal to produce electricity. Mercury is naturally occurring in coal and other fossil fuels and becomes airborne when these materials are burned. It is then deposited into lakes, rivers, and oceans, where it is transformed into methylmercury via a complex interaction with aquatic microbes.
The Environmental Protection Agency (EPA) website explains that “Methylmercury, a highly toxic organic compound, is the form of mercury people in the United States encounter most frequently ... Nearly all methylmercury exposures in the United States occur through eating fish and shellfish that contain higher levels of methylmercury.”
Nearly everyone has detectable levels of methylmercury in their blood. In 2000, the EPA published a “Reference Dose for Methylmercury” offering guidelines for a level of exposure to methylmercury considered safe for the general population to ingest daily and over a lifetime, and without risk of adverse effects. The reference dose (RdF) was set at 0.1 micrograms (mcg) of methylmercury per kilogram of body weight, per day. Since most people don’t eat fish every day, this number can be multiplied by seven to determine a “safe” level of consumption per week. So for example, a “safe” dose for a person weighing 65 kg (143 pounds) would be (0.1 mcg) x (65 kg) x (7 days) = 45.5 mcg.
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This weekly reference dose can then be compared with the total amount and type of fish consumed per week by using an online mercury calculator such as those provided by OMNI calculator or Seatopia. There we can easily calculate that, for a 143-pound person, two six-ounce servings of salmon per week contain 16.3 micrograms (mcg) of mercury—well within the 45.5 mcg limit—while two six-ounce servings of Chilean sea bass provide a concerning 121.4 mcg of mercury.

Since both levels of omega-3, and methylmercury concentrations vary widely between seafood species, it is possible that someone who follows the general guideline of eating fish “at least twice a week” could be getting inadequate amounts of omega-3s, while simultaneously ingesting methylmercury at potentially toxic levels.

Filling the Gaps

In response to these concerns, the Environmental Working Group (EWG) developed a Consumer Guide to Seafood which addresses shortcomings in the FDA and EPA recommendations. The guide criticizes the “safe” reference levels for mercury set by the EPA based on research conducted prior to 2001, since more recent studies have shown that, for the developing fetus and young children in particular, observable harm can occur at lower levels.
Even if a pregnant woman’s intake of methylmercury is within the “safe” levels established by the EPA, the amount her unborn child receives in utero could be much higher. A review article published in the July 2011 Journal of Toxicology pointed out that “MeHg crosses the placenta, and levels in umbilical cord blood are about 1.7 times as high as the mother’s blood levels ... The developing nervous system is known to be particularly vulnerable to MeHg; effects depend on both the dose and the timing of exposures. Prenatal exposure to MeHg can result in cognitive deficit, motor skill effect, attention deficits, language skill deficiencies, and decreased learning capacity and memory.”
The FDA published a fact sheet titled “Advice About Eating Fish” which categorizes many commonly eaten types of seafood into “Best choices,” “Good choices,” and “Choices to Avoid,” based on each species’ estimated level of methylmercury, and encourages pregnant and breastfeeding women to eat 8–12 ounces weekly from the “Best Choices” list, or four ounces from the “Good Choices” list.

As the EWG guide points out, these recommendations fall short in failing to also inform the public about the levels of omega-3s found in each species, noting that “Twenty-one of the 35 common fish and shellfish we investigated would not provide an adequate amount of omega-3s when eaten twice weekly. This includes most fish and shellfish species often found in the American diet.”

Cooking methods also affect the nutritional value of seafood. Ms. Anderson advises, “The best methods to retain the omega-3 content of seafood is either baking, boiling, steaming, microwaving, sous vide, or poaching. In contrast, direct heat from roasting, pan frying, and submersion from deep frying can reduce the EPA and DHA levels in fish.”

To receive the many benefits of omega-3s from seafood, while limiting exposure to methylmercury, involves a little research and something of a balancing act. The Environmental Working Group’s online Seafood Calculator is free, easy to use, and offers a personalized breakdown of the best seafood options which are both high in omega-3s and low in methylmercury.

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Zrinka Peters
Zrinka Peters
Author
Zrinka Peters is a freelance writer focusing on health, wellness, and education. She has a bachelor's degree in English literature from Simon Fraser University in British Columbia, Canada, and has been published in a wide variety of print and online publications including Health Digest, Parent.com, Today's Catholic Teacher, and Education.com.
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