Is Your Shark Meal Poisoning You? Latest Research Says Yes.

The myths swirling around sharks are numerous.

“Man-eating monsters…”

“Sharks are mindless killers…”

“Megalodon still exists…”

“They can’t get cancer and are immune to disease…”

All of these have been debunked. Yet many still believe that consuming shark-derived products will promote vitality and health instead of what it actually does: pose a health risk to consumers, especially women of childbearing age. But for many communities around the world, these products are an important – if not only – source of protein for them.

“That’s why we need to get a better idea what health risks might be facing those communities,” Laura García Barcia, a Florida International University (FIU) Ph.D. candidate, said.

García Barcia, part of FIU’s Predator Ecology and Conversation lab, collaborated with a team of scientists from the United States and Hong Kong to assess the health risks of eating shark-derived products. They focused on one of the biggest safety concerns associated with consuming these products — mercury. Found naturally in our planet, this heavy metal is released into the environment in several ways (some manmade, like burning coal, or natural events like eruptions). Marine life absorbsmethylmercury — the organic form of mercury — from their food and from their surrounding environment as water passes over their gills. Tightly bound to the proteins in all sea life tissue, it “bioaccumulates” as you move up the food chain. Picture this: methylmercury gets absorbed by phytoplankton, which are then eaten by zooplankton, which are gobbled up by small fish and so on and so forth. As methylmercury is absorbed by bigger animals — which tend to live longer and eat more things — larger fish species tend to accumulate a lot more methylmercury in their body than smaller fish. Expectant mothers and parents of young children know to limit certain seafood intake to avoid these high levels of mercury, staying away from any seafood with the ominous warning: “High in Mercury.” But is mercury that bad for us?

Yes. While mercury isn’t exactly the issue since it occurs naturally at low levels, methylmercury is highly toxic. It causes serious health problems when it reaches certain levels in your body. Seafood has been pointed out to be the source of nearly all the methylmercury that we acquire in our human bodies and presents the greatest risk to fetuses, infants, and children – their growing brains and nervous systems can be adversely affected by this toxin. But some communities don’t have the luxury to choose a “safer” seafood option and rely mostly, if not solely, on shark-derived products.

“After the first study we did in 2020, the next question we wanted to answer was how many bowls of shark fin soup — or how much shark meat — you can have without consuming too much mercury,” explained García Barcia. Typically, shark fin soup is reserved for special occasions, so people only have anywhere between one to six bowls a year. However, researchers have warned in the past that due to high methylmercury levels in many shark species people should limit their intake of this.

In order to answer this question, they needed some fins sold for human consumption. Luckily, they had fin trimmings on hand, previously collected from markets in China and Hong Kong as part of a larger, ongoing project to understand the species composition of the global shark fin trade. Most of the meat and fin samples tested had mercury levels surpassing local legal safety limits, while the greatest risk to consumers is from hammerhead shark products. The findings were recently published in Exposure & Health. The team set out to test mercury levels in the nine most common shark species that end up in the fin trade — since these would most likely end up in a bowl of shark fin soup. Out of the 267 fin trimmings, 75% exceeded the Hong Kong Center for Food safety’s maximum legal limit of 0.5 parts per million (ppm) of methylmercury.

Hammerhead species had the most staggeringly high amounts of mercury. Great hammerhead fins had the highest methylmercury levels, ranging from between 0.28 and 26.24 ppm. Scalloped hammerhead fins had 0.26 to 10.20 ppm, and smooth hammerhead fins between 0.17 and 25.53 ppm. Some hammerhead shark samples were over 20 times the limit of 1 ppm. “Hammerheads are one of the premium species in the fin trade, yet the high-end consumers who buy them probably don’t realize that by purchasing the most expensive fins they actually are putting themselves and their guests at the greatest health risk,” said Dr. Demian Chapman, one of the study’s authors and director of the Sharks & Rays Conservation Program at Mote Marine Laboratory & Aquarium and adjunct professor at FIU. “The fin trade has contributed to the high extinction risk faced by the hammerhead sharks, yet trading these species in particular also puts consumers at risk. It’s a lose-lose scenario for people and wildlife.”

While the global shark fin trade has contributed to a rise in shark fishing — and this includes the illegal shark fishing and trade — recent reports show that demand for shark meat across the world is also growing. In fact, the meat trade is beginning to surpass the fin trade in volume and value. This change poses questions into how shark meat could also introduce mercury into a person’s diet.

For this question, the team analyzed 33 meat samples sold in Trinidad and Tobago, where shark meat is frequently consumed. Scalloped hammerhead (Sphyrna lewini) and Atlantic sharpnose shark (Rhizoprionodon terraenovae) meat had the highest levels of mercury, surpassing local safety consumption limits of 1 part per million — and should be avoided, particularly by anyone who relies on a lot of shark meat in their diet. Some hammerhead samples were 2 to 3 times that 1 ppm limit. “The differences in health risk between species is striking and we encourage both governments and consumers to start questioning what species end up on a plate,” García Barcia said. This is an especially poignant point as most health advisories focused on the risk of mercury toxicity in shark products are treated with a broad brushstroke, listing all shark species. But as this study shows, certain species — like hammerheads — pose a greater risk than others.