As a sushi lover, I’ll take any excuse to go grab sashimi — but it’s important to choose seafood carefully due to risks like mercury exposure.
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Mercury is a toxic metal that can lead to some unwanted health impacts, both overall and to our hair growth. Evidence shows that increased levels of mercury are associated with negative effects to the digestive, immune, and nervous system, as well as higher instances of hormonal disorders and autoimmunity. Increased mercury levels can even cause changes to the expressions of our genes that are linked to issues such as diabetes and heart disease. By causing disruptive hormone signaling and inflammation, these imbalances are stressors on the inner workings of our bodies.
While every organ in your body can be impacted by mercury exposure, our hair is especially impacted when ingesting high amounts. Internal stress can come in many forms, but they all have the potential to send your hair running from its growth phase into its resting and shedding phases. Plus, unwanted inflammation can impact our ability to digest necessary nutrients for hair growth.
Rising mercury levels in ocean life
Concentrations of methylmercury in fish have increased significantly over the last few decades, and experts agree this is due to both climate change and overfishing. A 2018 study identified the human activities most responsible for releasing mercury into our air, soil, and water are coal combustion, mining, and cement production. A staggering 80% of this mercury deposits into our oceans, where it’s turned into the toxin methylmercury by microorganisms and then ingested by unknowing fish.
While our industrial practices around mercury have improved in recent years, changes to our global environment and practices have still encouraged a spike in methylmercury concentration in fish. The increasing temperature of the sea has caused small fish to have higher-energy needs, leading them to eat more mercury-laden prey than they did previously. For these fish, it may not add up to much of a change. But mercury exposure has the tendency to stick around and accumulate, so as these small fish are continually eaten by bigger fish, the overall impact becomes more apparent. These small fish pass on the mercury they’ve collected to the large fish, who continue to build their own internal collection until they finally end up on our dinner plates. And then guess who gets passed the mercury baton? Us.
According to the Food and Agriculture Organization of the United Nations (FAO), fish production for human consumption is up 21% from the 1960s, and the unforeseen impact of our overfishing has finally reached us on the food chain. For example, our overfishing of Atlantic cod’s favorite meals like sardines have forced them to pursue higher-mercury food options like lobster and large herring, which then causes them to have a higher mercury concentration by the time they make it to our plates.
High mercury fish to avoid
Decreasing your personal exposure to mercury doesn’t have to mean swearing off all seafood. The U.S. Food and Drug Administration (FDA) continually recommends at least eight ounces of seafood per week for most adults as part of a healthy eating pattern, thanks to their easily-digestible protein, high omega-3s, and a variety of important vitamins and minerals. However, keeping your mercury levels low does likely mean avoiding the worst culprits. According to the Environmental Working Group (EWG) and the FDA, the biggest offenders for high mercury content fish are as follows.
10. Orange roughy
This deep-dwelling fish can be found worldwide, but the orange roughy is most commonly found in New Zealand and Australia. This fish can live up to 100 years, giving it plenty of time to accumulate mercury. One four ounce serving contains 132% of your recommended weekly mercury consumption; with 100% being the recommended highest threshold of general mercury consumption.
9. Bigeye tuna
Commonly found in the Pacific Ocean, this species of tuna is usually priced more affordably than its cousin, bluefin tuna, and is often included in sashimi preparations. One four ounce serving contains 141% of your recommended weekly mercury consumption.
8. Bluefin tuna
The largest species of tuna, the speedy bluefin can live up to 40 years and spends its life migrating across all oceans. Bluefin tuna are known to be spectacular predators, with their prey of choice being schools of herring, mackerel, and occasionally eels. One four ounce serving contains 181% of your recommended weekly mercury consumption.
7. Striped marlin
This fish can reach a whopping 12 feet in length and weigh over 450 pounds, solidifying its place in the “big fish” category. Striped marlins are found primarily in the warmer waters of the Indian and Pacific oceans. One four ounce serving contains 201% of generally recommended mercury consumption.
Shark fin soup has become such a popular delicacy, it’s part of the reason some shark species have found themselves on the International Union for Conservation of Nature (IUCN) Red List of Threatened Species. While not at the top of the mercury list, sharks vary so significantly in size that it’s no surprise their maximum mercury content can easily test higher than other fish. Mercury ranges in tested samples vary as widely as 0.05 mg to 13.23 mg. Sharks have a greater chance of ingesting mercury because they’re so long-lived, which makes them a risky choice both for your dinner and when used in cartilage supplements. One four ounce serving contains 204% of your recommended weekly mercury consumption.
Previously a restaurant staple, swordfish have now found themselves on many vulnerable species lists. A fast-swimming fish with a long bill to slice prey, they have a reputation to be successful, predatory fish — so naturally, swordfish gobble up a significant amount of smaller, mercury-laden fishes. One four ounce serving contains 206% of your recommended weekly mercury consumption.
4. King mackerel
Despite their smaller size, king mackerels still make it to the top four of the FDA’s mercury list. Growing to about 20 to 35 inches in length, they prefer hanging out in warmer climates and adopt a diet of small schooling fish. One four ounce serving contains 255% of your recommended weekly mercury consumption.
3. Gulf tilefish
These large, slow-growing fish can be found in the deep waters of the Gulf of Mexico. A study published in 2019 found that around 90% of tested tilefish far surpassed the U.S. regulations on recommended thresholds for mercury. One four ounce serving contains 336% of your recommended weekly mercury consumption.
Several species of marlin exist, and all of them carry the similar characteristics of being long-nosed carnivores of impressively huge size. They primarily feed on other fish, which is likely the reason behind their significant accumulation of mercury. One four ounce serving contains 352% of your recommended weekly mercury consumption.
1. Blue marlin
These massive fish can reach nearly 2,000 pounds and live over 20 years, making them one of the biggest fish species in the world. Blue marlins spend most of their lives out in the depths of the sea, migrating along warm ocean tides for thousands of miles. Thanks to their meals of choice, which include other fish on this list, they earned #1 spot. One four ounce serving contains 588% of your recommended weekly mercury consumption.
Stick with smaller fish
You may have heard that smaller fish tend to contain less mercury, and it’s true! Bigger fish are usually higher up on the food chain, meaning they’re more likely to have eaten greater amounts of smaller fish and inherited each meal’s individual mercury load.
Low mercury fish to consider include:
- Atlantic mackerel
- Rainbow trout
- North Atlantic cod
If you’re looking for other seafood options, consider oysters, mussels, scallops, pacific clams, crayfish, shrimp, king crab, and squid.