Trace Metals (Cd, Co, Cr, Cu, Hg, Ni, Pb, and Zn) in Food Supplements of Marine Origin

ABSTRACT

We determined the concentrations of Cd, Co, Cr, Cu, Hg, Ni, Pb, and Zn in dietary supplements of marine origin. Four supplement categories were studied; algae, coral, krill, and shark cartilage. A direct mercury analyzer was used for Hg determinations while acid digestions and ICP-AES were used for Cr analysis and ICP-MS for the other trace metals. Algae are the supplements showing the highest concentrations of Pb, Cr, and Ni with respective means of 1.6 mg Pb/kg dry weight (d.w.), 3.2 Cr mg/kg d.w., and 8.0 mg Ni/kg d.w. Krill supplements have the highest levels of Cd, Cu, and Zn with 0.65 mg Cd/kg d.w., 63 mg Cu/kg d.w., and 50 mg Zn/kg d.w., respectively. Shark cartilage supplements show the highest levels of Hg and Co with mean concentrations of 160 μg Hg/kg d.w. and 73 ± 51 μg Co/kg d.w., respectively. No samples in our study exceeded the provisional tolerable daily intakes set by Health Canada, the joint committee of the World Health Organization/Food and Agricultural Organization, or the U.S. Environmental Protection Agency. Nevertheless, Ni and Pb in algae and Hg in shark cartilage may end up contributing to a very significant portion of the allowable daily intake—leaving little room for normal intake through food consumption and other exposure pathways.

Key Words:

• algae
• coral
• krill
• shark cartilage
• trace metals
• nutraceuticals
• natural health products
• dietary supplements

ACKNOWLEDGMENTS

Thanks go to Carmen Donisa, Hélène Lalande, and Dominic Bélanger for their help with the analytical work. Financial support was provided by the Natural Sciences and Engineering Research Council of Canada.

Notes

^†The maximum allowable daily intake for methylmercury is 0.1, albeit we have measured total Hg, for shark cartilage, we expect 95% of the mercury to be methylmercury (Krystek and Ritsema 2005).