Shark Meat and Cartilage Contain Neurotoxins Linked to Alzheimer’s, Study Warns

A variety of shark species from the Atlantic and Pacific Oceans have high concentrations of two toxins linked to neurodegenerative diseases like Alzheimer’s in their fins and muscles, according to researchers at the University of Miami.

Their study, “Cyanobacterial Neurotoxin BMAA and Mercury in Sharks,” published in Toxins, suggests that restricting the consumption of sharks may have beneficial health effects, and also improve shark conservation, since a number of the analyzed shark species are at risk of extinction due to overfishing.

Shark products are widely consumed in Asia and globally in Asian communities. Currently, shark fin soup is in increasingly high demand, a popular food at weddings and other celebrations. Other shark products, such as shark cartilage, are included in dietary supplements as a source of traditional Chinese medicine, and have gained popularity in Western nations.

But concern is growing as to the potential health consequences of consuming shark parts, including fins, meat, and cartilage. Researchers have  reported that the neurotoxin methyl mercury tends to bioaccumulate in sharks over their lifespans, and recent studies have also revealed the presence of pro-inflammatory compounds in commercial shark cartilage supplements that could pose health risk for consumers.

“Since sharks are predators, living higher up in the food web, their tissues tend to accumulate and concentrate toxins, which may not only pose a threat to shark health, but also put human consumers of shark parts at a health risk,” Neil Hammerschlag, a research assistant professor at the UM Rosenstiel School and UM Abess Center for Ecosystem Science and Policy, and the study’s lead author, said in a press release.

The team collected fins and muscle tissue samples from 10 shark species found in the Pacific and Atlantic, which included some endangered species at risk of extinction due, in part, to overfishing. These samples were then examined for the presence of mercury and another neurotoxin called β-N-methylamino-L-alanine (BMAA). “Recent studies have linked BMAA to neurodegenerative diseases such as Alzheimer’s disease and amyotrophic lateral sclerosis (ALS),” said Deborah Mash, a professor of Neurology and the study’s senior author.

They found that all shark species have concentrations of mercury and BMAA that could pose a threat to human health. And because they are both at high levels, the researchers believe they could have synergistic negative effects on consumers.

“Our results suggest that humans who consume shark parts may be at a risk for developing neurological diseases,” said Mash.

“Limiting the consumption of shark parts will have positive health benefits for consumers and positive conservation outcomes for sharks, many of which are threatened with extinction due in part to the growing high demand for shark fin soup and, to a lesser extent, for shark meat and cartilage products,” Hammerschlag said.