Is Shark Fin Soup a Threat to Brain Health?

Fins found to contain high concentrations of a neurotoxin linked to degenerative brain diseases.

Coral Gables (February 28, 2012) — Sharks, which are among the most threatened of marine species, are killed primarily for their fins alone to fuel the growing demand for shark fin soup, an Asian delicacy. Now, a new study by University of Miami scientists in the journal Marine Drugs has found that shark fins contain high concentrations of BMAA, a neurotoxin linked to neurodegenerative diseases in humans including Alzheimer’s and Lou Gehrig’s disease (ALS). The study suggests that consumption of shark fin soup and cartilage pills may pose a significant health risk for degenerative brain diseases.

“Shark fins are primarily derived through finning, a practice in which shark fins are removed at sea and the rest of the mutilated animal is thrown back in the water to die,” said co-author Neil Hammerschlag, research assistant professor of marine affairs and policy and director of the RJ Dunlap Marine Conservation Program (RJD) at UM.

“Estimates suggest that fins from as many as 70 million sharks end up in soup. As a result, many shark species are on the road to extinction. Because sharks play important roles in maintaining balance in the oceans, not only is shark fin soup injurious to the marine environment, but our study suggests that it is likely harmful to the people who are consuming them,” Hammerschlag said.

Seven species of shark were tested for this study: blacknose, blacktip, bonnethead, bull, great hammerhead, lemon, and nurse sharks. Samples were collected from live animals in waters throughout South Florida.

“The concentrations of BMAA in the samples are a cause for concern not only in shark fin soup but also in dietary supplements and other forms ingested by humans,” said study co-author Deborah Mash, director of the University of Miami Brain Endowment Bank, which supports basic and clinical research and houses one of the world’s largest collections of postmortem human brains encompassing a wide range of neurological disorders.

In 2009, Mash and co-authors published a study in the journal Acta Neurological Scandinavica, demonstrating that patients dying with diagnoses of Alzheimer’s Disease and ALS had unusually high levels of BMAA in their brains, whereas healthy people had no BMAA or only trace quantities of the toxin present.

The shark study found a similar range and even higher BMAA levels in the fins tested. The new study found levels of between 144 and 1836 ng/mg of BMAA, “which overlapped the levels we measured in the brains of Alzheimer’s and ALS victims,” said Mash. This level, according to Mash, fits with the levels of BMAA that researcher Paul Cox discovered in fruit bats, animals that concentrate BMAA from their diet of cycad seeds. He linked ingestion of fruit bats to the severe ALS/Parkinsonism dementia that afflicted many people in Guam.

“Not only does this work provide important information on one probable route of human exposure to BMAA, it may lead to a lowering of the demand for shark fin soup and consumption of shark products, which will aid ocean conservation efforts,” said Hammerschlag.

The project was funded through a generous donation from the Herbert W. Hoover Foundation. Established in 1990, the foundation takes a leadership role in supporting unique opportunities that provide solutions to issues related to the community, education, and the environment.

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Shark fins drying in the sun in Kaohsiung before processing. Thirty percent of the world’s shark species are threatened or near threatened with extinction. Photo Credit: Shawn Heinrichs for the Pew Environment Group.

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