Heavy Metals in Fish & Seafood: Should We Be Worried?

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I am a huge seafood fan, so when I hear concerns from you about whether seafood is safe to eat, I definitely want to talk about it! One of the biggest concerns about seafood is the bioaccumulation of heavy metals from pollution in the oceans.

It can be confusing to know what fish or seafood is safe to serve, especially in a sensitive time like pregnancy or breastfeeding.

Let’s take a look at some of the concerns and what the current research says, and how we can make the best choice for our families.

Pollution in Fish & Seafood: Is It a Problem?

Fish can contain various contaminants because of their environment. These contaminants come from agricultural and industrial pollutants.

Persistent organic pollutants, or POPs, are in every ocean and every type of fish.

For this reason, many people fear that eating fish is no longer safe. However, let’s start with the good news about POPs:

Recent studies show that the levels of pollutants have consistently dropped over the past 30 years. A 2016 study in particular (cited below) claims levels have dropped 15 – 30% each decade.

The takeaway: The average fish now contains 50% fewer POPs than it did in the 1980s.

If our oceans are polluted, why the downward trend?

Since 2001, 152 countries have agreed to ban or eliminate the 12 most common POPs. This means the reduction could be because of bans on POPs. It could also be the result of dietary changes in marine life as they adapt to changing environments.

Researchers are quick to say that another 10 years of study are needed before we can know if this is a long-term trend.

Heavy metals are a hot topic, as I explain in this post. We encounter them in makeup, food, building materials, and more. You’ve probably heard that heavy metals can build up in fish, too.

Some of the most common heavy metals that contaminate seafood are:

  • lead
  • cadmium
  • arsenic
  • and mercury

For many people, the biggest concern is methylmercury, which is made from inorganic mercury that our bodies cannot process.

Inorganic mercury comes from industrial waste, smokestack emissions, volcanoes, and coal powered factories. Aquatic organisms convert this inorganic mercury into methylmercury.

According to the Food and Drug Administration (FDA), methylmercury is found in small concentrations in all seafood. However, they also claim that in many species of fish the levels are safe for most people to eat.

If you want to learn more about how to detox from heavy metals, check out this podcast.

Is Fish Safe for Pregnant and Nursing Mothers?

If you’ve been pregnant, you already know… pregnant women get all kinds of (sometimes unwanted) advice! A hot topic of course is what food an expectant mom should eat.

Expectant mothers know that high quality, nutrient-rich foods are essential to the health of the baby. Many caution pregnant women against eating seafood. However, seafood contains many of these necessary nutrients.

Just one of these nutrients is omega-3 fatty acids, which is crucial for brain development. One of the best and most common sources of long-chain omega-3s is seafood.

You can read one of my posts on the importance of omega-3s to learn more, but here is some evidence:

  • A 2008 study encourages mothers to eat more fish for baby’s optimal neural development.
  • In 2014, the FDA and EPA issued a statement that pregnant/nursing mothers and young children should eat 2-3 servings of fish per week!

Continue reading to learn about the best and safest fish to eat, whether or not you’re an expectant mother.

Do Fish Naturally Have Mercury in Them?

Fish naturally have a small amount of mercury. This mercury does not only come from pollution. Mercury also gets into the ocean from natural sources (volcanoes and soil runoff).

While methylmercury is a concern, few fish contain harmful levels. Mercury becomes an issue when levels get high through bioaccumulation.

What Is Bioaccumulation?

Bioaccumulation is the process by which pollutants collect in an organism faster than they can be excreted or metabolized, and it is a result of the food chain. Bigger fish eat smaller fish. Just like us, fish are what they eat. Fish absorb contaminants from their food.

Smaller fish have smaller amounts of heavy metals. This changes with each ascending step in the food chain. Top feeders, like marlin and swordfish, are high in heavy metals, especially methylmercury.

Marine mammals are very high in methylmercury because of bioaccumulation. Marine mammals are still used as food in parts of the world. Studies on the effects of methylmercury have been done in locations where marine mammals were a diet staple.

The famous study in the Faroe Islands showed devastating effects on children whose mothers ate seafood high in methylmercury. This study prompted a warning on eating fish, especially for pregnant and nursing mothers.

However, the waters around the Faroe Islands were heavily contaminated. Also, these mothers and children were eating seal, shark, and whale meat, not regular fish.

Farm-Raised vs. Wild-Caught Fish

Ocean-caught fish is a great source of selenium. The selenium actually binds to methylmercury and eliminates the risk to our bodies.

Farm-raised fish does not have selenium in it. Farms try to mimic the natural diet and environment of fish. Even the best farm cannot produce fish with the same nutrients as wild caught.

Read more about the differences between farm raised and wild caught fish in this post.

All fish contain some mercury, however, many contain very little. Small fish that are lower on the food chain are best because they do not bioaccumulate POPs and methylmercury.

Fish with a short life span are better choices than longer living, larger fish. Anchovies, herring, and sardines are great options. They are nutrient-dense and low in anything that could be a potential health concern.

Here is a shopping guide for popular fish:

Good choices:

This list includes fish that have shorter lives and are lower on the food chain. Both decrease the levels of mercury and POPs in fish. As a general rule, always opt for wild caught instead of farmed, and domestic over imported.

  • Sardines (my favorite)
  • Anchovies
  • Herring
  • Butterfish
  • Wild caught Pacific or Alaskan Salmon
  • Trout
  • Cod (Pacific is more sustainable)
  • Arctic Char
  • Halibut (Pacific)
  • Mackerel
  • Mussels (I buy them canned and smoked)
  • Oysters
  • Squid
  • Sablefish
  • Pollock
  • Alaskan King Crab
  • Haddock
  • Shrimp
  • Scallop
  • Lobster

Fish to Avoid:

  • Farmed fish
  • Imported Fish, especially from Southeast Asia
  • Tilefish
  • King Mackerel
  • Bluefin Tuna
  • Swordfish
  • Catfish
  • Shark
  • Chilean Sea Bass (high in mercury and endangered)
  • Orange Roughy (high bioaccumulation because of its long life and overfished)
  • Eel
  • Imported King Crab
  • Atlantic Salmon
  • Norwegian Salmon (over-farming has had a negative impact on even wild fish in Norway)

What I Do

Fish is an important part of every diet. There are some that should be avoided. However, most fish are safe to eat. Understanding what makes fish safe is the first step in choosing well.

Whenever possible, we source our fish through our local fish market using the guidelines above. I also keep frozen and canned fish and seafood in the freezer and pantry for busy nights. These companies have high quality standards and will deliver right to your home:

  • Thrive Market – My go-to budget option for quality seafood for the pantry. They have their own brand of sardines and tuna that beat everything else I’ve tried for quality and taste. You do need a subscription to order from Thrive Market, but I’ve found it’s worth it in every way.
  • Vital Choice – Listen to this podcast from founder Randy Hartnell and you’ll understand why this company is my go-to for frozen seafood. Their standards for sourcing are incredibly high (and you can tell from how it tastes!).

For additional help on the go, I recommend the Seafood Watch app put out by Monterey Bay Aquarium.

Who knows… now that you know the benefits of fish, maybe you’ll whip up one of my seafood recipes. Let “minnow” if you like it!

This article was medically reviewed by Madiha Saeed, MD, a board certified family physician. As always, this is not personal medical advice and we recommend that you talk with your doctor.

Do you consider the level of metal when choosing your seafood? What’s your favorite seafood recipe used at home?


  1. American Heart Association. (2018, March 1). How can I eat more nutrient-dense foods? Retrieved from https://www.heart.org/en/healthy-living/healthy-eating/eat-smart/nutrition-basics/how-can-i-eat-more-nutrient-dense-foods
  2. Bonito, L., Hamdoun, A., & Standin, S. (2016, February 04). Study finds toxic pollutants in fish across the world’s oceans. Retrieved from https://scripps.ucsd.edu/news/study-finds-toxic-pollutants-fish-across-worlds-oceans
  3. Bosch, A. C., O’Neill, B., Sigge, G. O., Kerwath, S. E., & Hoffman, L. C. (2016, January 15). Heavy metals in marine fish meat and consumer health: A review. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/26238481
  4. Center for Food Safety and Applied Nutrition. (n.d.). Questions & Answers from the FDA/EPA Advice on Eating Fish. Retrieved from https://www.fda.gov/food/consumers/questions-answers-fdaepa-advice-about-eating-fish-women-who-are-or-might-become-pregnant#V
  5. Center for Food Safety and Applied Nutrition. (2017, January). Eating fish: what pregnant women and parents should know. Retrieved from https://www.fda.gov/food/consumers/advice-about-eating-fish
  6. Dórea, J. G. (2009). Risks of mercury exposure related to gestational fish consumption: Beyond the sea. Reproductive Toxicology, 28(1), 113-114. doi:10.1016/j.reprotox.2009.03.008 Retrieved from https://www.sciencedirect.com/science/article/abs/pii/S0890623809000653
  7. Innis, S. M. (2008). Dietary omega 3 fatty acids and the developing brain. Brain Research, 1237, 35-43. doi:10.1016/j.brainres.2008.08.078 Retrieved from https://pubmed.ncbi.nlm.nih.gov/18789910/
  8. Nichols, P. D., Petrie, J., & Singh, S. (2010, May 26). Long-chain omega-3 oils-an update on sustainable sources. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3257669/
  9. United Nations University. (2012, February 23). Persistent organic pollutants in the marine food chain. Retrieved from https://unu.edu/publications/articles/persistent-organic-pollutants-in-the-marine-food-chain.html
  10. National Institute of Standards and Technology. (2018, August 27). Many Arctic pollutants decrease after market removal and regulation. Retrieved from https://www.sciencedaily.com/releases/2018/08/180827180752.htm
  11. Weihe, P., & Joensen, H. D. (2012). Dietary recommendations regarding pilot whale meat and blubber in the Faroe Islands. International Journal of Circumpolar Health, 71(1), 18594. doi:10.3402/ijch.v71i0.18594 Retrieved from  https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3417701/
  12. Willcox, D. C., Scapagnini, G., & Willcox, B. J. (2014, January 21). Healthy aging diets other than the Mediterranean: A focus on the Okinawan diet. Retrieved from https://pubmed.ncbi.nlm.nih.gov/24462788/
  13. Yousafzai, A. M., Ullah, F., Bari, F., Raziq, S., Riaz, M., Khan, K., . . . Ahmad, H. (2017). Bioaccumulation of some heavy metals: analysis and comparison of Cyprinus carpio and Labeo rohita from Sardaryab, Khyber Pakhtunkhwa. BioMed Research International,2017, 1-5. doi:10.1155/2017/5801432 Retrieved from https://www.hindawi.com/journals/bmri/2017/5801432/

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