Shark Fin Consumption May Expose People to Neurotoxic BMAA

Shark-fin soup has gotten a bad rap since conservation groups began raising awareness of shark finning, a practice in which fishermen slice the fins off the animals, sometimes while they are still alive, and discard the bodies overboard. Now, scientists have found another reason to avoid the Asian delicacy: it may be detrimental to neurologic health. Worldwide, an estimated 26–73 million sharks are traded on the fin market annually. Shark fin and cartilage are also sold as powder or in capsules, and traditional Chinese medicine claims it nourishes the blood, enhances appetite, and energizes multiple internal organs. Administration has not confirmed any health benefits, and a 2004 court injunction required one company to pay restitution to customers who purchased shark-fin products falsely claiming to treat cancer and HIV. 3 Deborah Mash, a neuroscientist at the University of Miami Medical School, led the first study to show shark tissues contain the neurotoxic amino acid β-methylamino-l-alanine (BMAA). 4 The nonprotein amino acid is produced by cyanobacteria (sometimes called " blue-green algae "), which are often associated with nutrient runoff in coastal waters, although huge blooms also occur in the open ocean. BMAA has received attention due to increasing evidence that consumption of contaminated food or water may contribute to amyotrophic lateral sclerosis, Alzheimer disease, and Parkinson disease. 5 Mash collaborated with Neil Hammer-schlag, a University of Miami research assistant professor, who captured sharks in Florida coastal waters. BMAA was detected in 23 of 29 fin samples and in all species tested—nurse, great hammerhead, lemon, bull, bonnet head, black nose, and blacktip sharks—at concentrations of 144–1,836 ng/mg wet weight. BMAA levels in shark fins fell within the range Mash measured in a previous study 6 of the brains of humans who died from neuro degenerative disease, which she says suggests BMAA has biomagnified in these top predators. The scientists also tested a few samples of organ tissue from great hammerheads killed in recreational fisheries. BMAA levels averaged 1,450 ng/mg in kidney, 588 ng/mg in liver, and 58 ng/mg in muscle. None was detected in heart tissue. By comparison, eight hammer-head fins averaged 1,028 ng/mg. " What the shark is teaching us is that, like man, apex predators are probably getting exposed to BMAA through their diet, " says Mash. Past studies have detected high levels of BMAA in some fish and crustaceans in Florida waters, including pink shrimp and blue crabs, which both …