Analysis of Essential Minerals and Heavy Metals in Canine and Feline Dietary Supplements Marketed in the United States

Heavy metals have been documented in dietary supplements for people and animals. Cadmium, selenium, lead, and mercury are of particular concern. Our objective was to determine the concentrations of five essential minerals and 12 heavy metals in 70 canine and feline dietary supplements, and to evaluate potential toxicity risks. Our secondary objective was to compare the analysed concentrations to the content claims on product labels. Samples were analysed using inductively coupled plasma mass spectrometry. Concentrations were compared to maximum tolerable levels (MTL) established by the National Research Council. Beryllium, mercury, and thallium were not detected in any supplements. The most prevalent essential mineral was zinc (68 products). The most prevalent heavy metal was nickel (66 products); lead was detected in 16 supplements (median 0.145 mg/kg; 0.1-3.7 mg/kg) and cadmium was detected in 10 supplements (median 0.115 mg/kg; 0.1-1.5 mg/kg). Selenium, an essential nutrient with a narrow margin of safety, was detected in 52 samples (median 0.32 mg/kg; 0.1-14.0 mg/kg) but only declared as an ingredient in 10 products. Of 18 supplements with label claims for one or more of the minerals analysed, eight did not meet one or more claims. None of the analysed supplements exceeded the MTL for any mineral, suggesting that the risks are low when following label directions. However, species-specific MTL data are lacking for many minerals in dogs and cats, necessitating extrapolation with safety factors. More research is needed to characterise the risks of chronically high intakes of minerals by dogs and cats. Data presented as an oral abstract at the American Academy of Veterinary Nutrition 24th Annual Clinical Nutrition & Research Symposium and the 28th European Society of Veterinary & Comparative Nutrition Congress 2024.