Zinc Intake Is Associated with Lower Cadmium Burden in US Adults1–3

Background: Cadmium is a toxic transition metal whose absorption and accumulation might depend on zinc intake. Objective: We sought to determine whether zinc intake and serum zinc would be inversely associated with cadmium exposure. Methods: This study used data fromNHANES 2003–2012, fromwhich therewere 6678 and 6488 participants with urinary and blood cadmium data, respectively, and 1195 participants with serum zinc data. Mean blood and urinary cadmiumwere reported by quintiles of zinc intake and by the dose and duration of zinc supplement use. The associations between zinc intake from diet and supplements, serum zinc, and blood and urinary cadmiumwere determined usingmultiple regression. Analyses were adjusted for age, body mass index, race/ethnicity, gender, income-to-poverty ratio, education, smoking status, and mean intakes of energy, calcium, and iron. Results: Urinary cadmium concentrations were 0.04 mg/g creatinine lower among participants in the highest vs. lowest quintile of total zinc intake (P-trend = 0.0041). Zinc supplement dose and duration were inversely associated with blood cadmium (P = 0.0372) and serum zinc (P-trend = 0.0017), respectively. In adjusted regression models, a 10 % increase in total zinc intake corresponded to a predicted decrease in blood cadmium of 0.42 % (95 % CI: 20.79%, 20.06%; P = 0.0260) and in urinary cadmium of 0.42 % (95 % CI:20.81%,20.04%; P = 0.0340). A 10 % increase in serum zinc was associated with a predicted 1.99 % (95 % CI: 23.17%, 20.81%; P = 0.0012) decrease in blood cadmium and a predicted 4.09 % (95 % CI: 2.14%, 6.04%, P = 0.0001) increase in urinary cadmium. Conclusions: Dietary and serum zinc in US adults are associated with cadmium exposure, presumably by influencing the absorption and accumulation of cadmium. Whether the degree of reduction in cadmium exposure from greater zinc intake and status is causal or relevant from a public health perspective needs further investigation. J Nutr doi: 10.3945/jn.115.223099