Environmental neurotoxins β-N-methylamino-l-alanine (BMAA) and mercury in shark cartilage dietary supplements

Abstract

Shark cartilage products are marketed as dietary supplements with claimed health benefits for animal and human use. Shark fin and cartilage products sold as extracts, dry powders and in capsules are marketed based on traditional Chinese medicine claims that it nourishes the blood, enhances appetite, and energizes multiple internal organs. Shark cartilage contains a mixture of chondroitin and glucosamine, a popular nutritional supplement ingested to improve cartilage function. Sharks are long-lived apex predators, that bioaccumulate environmental marine toxins and methylmercury from dietary exposures. We recently reported detection of the cyanobacterial toxin β-N-methylamino-l-alanine (BMAA) in the fins of seven different species of sharks from South Florida coastal waters. Since BMAA has been linked to degenerative brain diseases, the consumption of shark products may pose a human risk for BMAA exposures. In this report, we tested sixteen commercial shark cartilage supplements for BMAA by high performance liquid chromatography (HPLC-FD) with fluorescence detection and ultra performance liquid chromatography/mass spectrometry/mass spectrometry (UPLC–MS/MS). Total mercury (Hg) levels were measured in the same shark cartilage products by cold vapor atomic fluorescence spectrometry (CVAFS). We report here that BMAA was detected in fifteen out of sixteen products with concentrations ranging from 86 to 265μg/g (dry weight). All of the shark fin products contained low concentrations of Hg. While Hg contamination is a known risk, the results of the present study demonstrate that shark cartilage products also may contain the neurotoxin BMAA. Although the neurotoxic potential of dietary exposure to BMAA is currently unknown, the results demonstrate that shark cartilage products may contain two environmental neurotoxins that have synergistic toxicities.