Delicacy linked to neurodegenerative diseases is another health risk to consumers already facing mercury hazard and criticism from conservationists
04, March 2012
Besides protecting the ecosystem, there may be another reason to avoid eating shark fin – your health.
The fins contain a high dose of a neurotoxin linked to neurodegenerative diseases, researchers have found. The neurotoxin BMAA is linked to such conditions as Alzheimer’s and motor neurone disease (also called Lou Gehrig’s disease), which causes loss of mobility in the limbs.
The study, which appeared last month in the journal Marine Drugs, suggests that eating shark’s fin soup or shark cartilage pills may pose a significant health risk for degenerative brain diseases. It was conducted by scientists at the University of Miami in the United States.
“Shark fins are primarily derived through finning, a practice whereby 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 and professor of marine affairs and policy.
“Estimates suggest that fins from as many as 70 million sharks end up in soup [a year],” he said in an interview posted on his university’s website. “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’s fin soup injurious to the marine environment, but our study suggests that it is likely harmful to the people who are consuming them.”
The researchers believe BMAA accumulates in sharks because they are at the top of the marine food chain. As a result, the high amounts of the neurotoxin potentially pose health risks to consumers of shark products.
Seven species of shark were tested: blacknose, blacktip, bonnethead, bull, great hammerhead, lemon and nurse sharks. Four of them – bull, great hammerhead, lemon and blacknose – can be found in Hong Kong, according to the city’s marine conservation group Bloom Association.
“The concentrations of BMAA in the samples are a cause for concern, not only in shark’s fin soup, but also in dietary supplements and other forms ingested by humans,” said Deborah Mash, also a member of the US research group.
In 2009, Mash and her colleagues published a study in the journal Acta Neurologica Scandinavica demonstrating that patients diagnosed with Alzheimer’s disease had unusually high levels of BMAA in their brains – up to 256ng/mg, whereas healthy people have no BMAA or only traces of the toxin present.
The shark fin study found even higher BMAA levels in the fins, as much as 1,836ng/mg.
Hammerschlag said: “Not only does this work provide important information on one probable route of human exposure and BMAA, it may lead to a lowering of the demand for shark’s fin soup and consumption of shark products, which will aid ocean conservation efforts.”
The study is not the first to show that shark fins may not be good for human health. A 2008 study found that the mercury content in Asian shark fins exceeded safe levels, posing a health risk especially to infants.
The joint study by San Francisco-based WildAid and Hong Kong’s EarthCare tested fin samples on the mainland and in Hong Kong, Singapore, Taiwan and Thailand. The samples contained mercury concentrations that exceeded each place’s safety standards, the study found. In Hong Kong, eight of 10 samples exceeded the Food and Environmental Hygiene Department’s limit of 0.5 parts per million.
Mercury in large doses “can cause a decrease in intelligence quotient, lack of co-ordination, blindness and seizures in children” as well as personality changes, deafness and memory loss in adults, according to Hong Kong’s Centre for Food Safety.
Shark fins with mercury content are expected to have a gradual and very small effect on consumers, but nonetheless, they pose a risk. Shark and other large predatory fish are at the top of the food chain, thus accumulating mercury from the smaller fish they eat. Sharks also live longer, collecting higher doses of mercury than other fish.
The fin is 83 per cent protein, the material to which mercury binds. The older tissue at the fin’s base, in particular, contains higher levels of mercury.
The European Union is the world’s largest exporter of shark fins. In November, the European Commission proposed a full ban on shark finning. In the US, states including California, Oregon, Hawaii and Washington have banned the sale of shark fins. New York is expected to join the pack early next year.
In China, 142 business leaders of companies such as Lenovo (SEHK: 0992, announcements, news) , Haier and China Merchants Bank (SEHK: 3968) pledged not to eat shark fin. Last year, 45 members of the Chinese People’s Political Consultative Conference signed a motion to develop regulations on banning the shark fin trade.
Hong Kong remains the global centre of the trade, but an increasing number of businesses are saying no to the delicacy. The Peninsula Hotels group has banned shark fin from its menus since the start of the year.
Even so, the delicacy is served at 93 per cent of the city’s top hotels, according to a survey by conservation group the Hong Kong Shark Foundation in January. It also found that 80 per cent of the hotels were offering three to five types of endangered sea life on their menus.
Hong Kong is said to handle half of the world’s shark fin trade, with Spain its biggest supplier.
Bertha Lo-Hofford, the foundation’s programme director, discourages the consumption of sharks because they mature late and reproduce slowly and have few offspring. If they become extinct, she warned, it could upset the delicate balance of the marine ecosystem. The depletion of sharks jeopardises the stability of the ocean because the species regulates the population of animals lower down the food chain, she said.
Bloom’s project co-ordinator Stanley Shea said shark fin traders, and restaurant and hotel managers, had noticed shark fin consumption decreasing at wedding banquets, festival dinners, new year family reunions and other occasions.
“More couples, especially the young, have requested no shark fin during their wedding banquets, and more families have started to ask for shark fin alternatives,” he said.
“Thanks to enduring efforts from environmental groups, people in Hong Kong seem to realise the importance of protecting sharks.”