Fish can be an excellent part of a healthy diet, providing important nutrients like omega-3 fatty acids which can lower your risk for diseases like cardiovascular disease, cancer, Alzheimer’s and dementia, age-related macular degeneration, and rheumatoid arthritis, among others . However, there are some fish you shouldn’t eat.
Unfortunately, due to human industrial activity like coal-fired electricity generation, smelting, and the incineration of waste, large amounts of mercury are ending up in our waterways, and subsequently, the fish that swim in them.
Once this mercury gets into the marine food chain, it “bioaccumulates.” This means that as smaller fish get eaten by gradually larger fish, the concentration of mercury at each level becomes greater .
Consuming too much mercury can be dangerous to your health, and lead to mercury poisoning. For this reason, the US Food and Drug Administration (FDA) and the US Environmental Protection Agency (EPA) have issued guidelines regarding how much mercury is safe for humans to ingest, and the non-profit Environmental Defense Fund (EDF), provides suggestions for which fish you shouldn’t eat .
16 Fish You Shouldn’t Eat (or eat less of)
Tilapia is one of the most widely consumed fish in America, but it contains very low levels of omega-3s and high levels of omega-6s, which is linked to inflammation throughout the body. Eating a diet with an adequate ratio of omega 3 to 6 fatty acids is important when trying to deal with chronic inflammation.
The main problem with most of the tilapia that is consumed in the US is that it is farmed, which does not have the same nutrition profile as wild-caught fish. A 2008 study revealed that the shift to consuming more farmed fish like tilapia has led to a larger consumption of inflammatory fatty acids, and thus inflammatory diets .
2. Atlantic Cod
The problem with Atlantic cod has less to do with your health, and everything to do with the environment and the fish population. Atlantic cod has been fished heavily for a thousand years, and in the late 1990s, the fishery collapsed. Fishing for Atlantic cod has been dramatically reduced since then, but the species has struggled to rebound. Scientists agree that the collapse of the fishery has fundamentally changed the North Atlantic food web, and the species is now considered vulnerable to extinction .
3. Atlantic Flatfish (halibut, flounder, and sole)
This is another case of overfishing and general waste. Commercial fisheries have what is referred to as “wasted bycatch”, which is when a fish or other marine species are caught unintentionally while catching other fish.
US fisheries throw about 2 billion lbs of wasted bycatch overboard every year. This is equivalent of about half a billion meals! The California gillnet fishery, which targets halibut, has been identified as one of the worst, and if you’ve eaten halibut in the US it likely came from this operation .
Caviar are the eggs of the Beluga Sturgeon, an ancient fish that can live for one hundred years. Its eggs are highly sought after and can be sold for thousands of dollars a pound. Because of this, this special fish is now highly vulnerable to extinction . The same goes for many other types of Sturgeon as well.
5. Chilean Sea Bass
In terms of the environment, this is another species that has been highly over-fished. In addition to that, its high mercury content poses a health risk to humans .
This is one fish you may want to avoid on the sushi menu. Eel are slow to mature and have been overfished in many parts of the world, causing some populations to collapse.
This is problematic because eels play an important role in spreading mussel populations, which act as natural water filters . Additionally, eels absorb and store harmful chemicals and pollutants very easily. This is such a problem that in some areas residents are advised to eat eel no more than once per year .
7. Farmed Salmon
The majority of the salmon consumer in the US is farmed, and farmed salmon may contain higher amounts of harmful contaminants like PCBs, which are linked to a litany of health problems like insulin resistance, obesity, cancer, and stroke .
Farmed Atlantic salmon are also often treated with antibiotics that make them higher in the inflammatory omega-6 fatty acids .
Some progress has been made
While farmed salmon has been shown to contain high contaminants when compared to its wild counterparts, the trend may be shifting. Between 1999 and 2011 PCBs in Norwegian farmed salmon has decreased significantly .
8. Imported Basa, Swai, Tra, Striped Catfish
In many cases, these fish are simply labeled “catfish”, and should be avoided. A 2016 study found that seventy to eighty percent of these fish were contaminated by Vibrio Bacteria, which is what causes most cases of shellfish poisoning .
9. Imported Farmed Shrimp
There are a number of pesticides that are used globally in shrimp production. All but one of them are banned in the United States. On top of that, these shrimps have often been treated with large quantities of antibiotics, and so any time you handle these raw shrimp you run the risk of being infected with antibiotic-resistant bacteria [13,21].
10. Imported King Crab
Around three-quarters of all crab sold in the United States is imported from Russia, where unsustainable fishing practices are very common. Technically, the only crab that was caught in Alaska can be called “Alaskan King Crab.” However, mislabelling is incredibly common, so it is important to know where your crab is coming from. If it says “imported” and “Alaskan” on the label, something is amiss and you should stay away .
11. Orange Roughy
These fish can live for several decades, and don’t typically reach sexual maturity until they’re at least twenty years old. They are another species that have been overfished, but because of their very slow reproduction cycles, they have an extremely difficult time recovering .
Orange Roughy are also known to have high levels of mercury .
Since sharks are at the top of the food chain, they have very high levels of mercury . They are also slow to mature and reproduce, and thus overfishing has depleted their populations as well.
13. Atlantic Bluefin Tuna
Bluefin tuna have been severely overfished, and are now considered to be highly vulnerable to extinction . They are also large predatory fish and thus contain high levels of mercury .
15. King Mackerel
Both King Mackerel and Spanish Mackerel have high levels of mercury and should be avoided, especially by women and children .
Grouper has moderately high mercury levels and is vulnerable to overfishing . It is also often the target for seafood fraud. The “grouper” that is for sale is often actually a cheaper form of fish that is being intentionally mislabeled .
The Role of Selenium in Mercury Toxicity
If you love fish but you are concerned about mercury toxicity, there is some good news for you- many of the fish that people routinely eat are high in selenium, which can play a significant role in preventing mercury poisoning .
This does not mean that you can eat as many high-mercury fish as you want, but if you do choose to eat some fish that have a higher content of the heavy metal occasionally, eating enough selenium will help to prevent any negative side effects.
The core message here is this: If you’re eating high selenium fish that is low to moderately high in mercury, the overall risk is lower. If you’re consuming fish is high in mercury but low in selenium (i.e. shark), its best avoid or to consume very rarely.
To learn more about the role of selenium when it comes to fish, and mercury toxicity, check this article out!
Fish To Eat More Of
This does not mean you have to give up fish altogether, but it highlights the importance of reading labels and knowing where your fish is coming from. Wild-caught Alaskan salmon, Pacific Sardines, and Atlantic mackerel are all high in omega-3s, as well as several other nutrients, and have less of a negative impact on the environment.
Other good choices include Albacore tuna that was caught in the US or Canada, Alaska Cod, Arctic Char, Rainbow Trout, among others. The EDF Seafood Selector provides a comprehensive list of the best seafood and fish to eat, including where it should come from and how it should be produced.
The Bottom Line
When you’re choosing which foods to eat, it is important not only to consider the impact that those foods will have on your health, but also the impact that they’re having on the planet. It is crucial that we as consumers make responsible choices to ensure that our planet- and all the organisms upon it- continue to thrive for future generations.