Deficient calcium, zinc, and iron intake on absorption of cadmium from diet

Background/Aim: In vitro and in vivo studies have demonstrated that deficient calcium, zinc, and iron dietary intake upregulates metal ion transporters to increase intestinal absorption. However, these gut transporters are not specific and bind to other metals, including cadmium. Few human studies have investigated whether deficient calcium, zinc, and iron intake increases intestinal absorption of dietary cadmium. Methods: We used enrollment data (2010-2012) from the Study of Environment, Lifestyle & Fibroids, a cohort of 1693 African American women ages 23-35 who reside in the Detroit, Michigan area. Whole blood cadmium concentrations (proxy for cadmium absorption) were measured in 1548 participants. Dietary and supplemental calcium, zinc, and iron intake was estimated using Block 2005 Food Frequency Questionnaire data; deficient intake was defined as <80% of the recommended daily allowance. Daily dietary intake of total grains was used as the proxy for dietary cadmium intake as grains are a major source of cadmium exposure in U.S. diet. We estimated the percent difference in blood cadmium concentrations per median daily intake of total grains (4.55 ounce equivalents) using multivariable linear regression, stratified by deficient and sufficient calcium, zinc, and/or iron intake. We restricted the analyses to never smokers with plausible values for total energy intake (>400 and <5000 kcal/day) (n=1087). We adjusted for age at enrollment, total energy intake, body mass index, height, education, and natural log-transformed blood lead concentrations. Results: The observed percent difference in blood cadmium concentrations in relation to intake of total grains was stronger among those with deficient intake of calcium, zinc, and/or iron (28%, 95% CI; 6, 53%) than among those with sufficient intake of all 3 essential nutrients (5%, 95% CI: -7, 19%). Conclusions: Our preliminary findings suggest that women with deficient calcium, zinc, and/or iron intake have increased absorption of cadmium from the diet.