New evidence of iron and zinc interplay at the enterocyte and neural tissues

Because combined iron-zinc supplementation regimens are employed with increasing frequency in field trials to combat co-occurring iron and zinc deficiencies, there is a growing concern for potential antagonisms between these 2 metals. Several supplementation trials hinted at such a competition, and the intestinal divalent metal transporter-1 (DMT1) has often been cited as a possible site for its occurrence. We summarize new evidence showing that although iron does seem to reduce the absorption of zinc, the DMT1 is an unlikely site for this absorptive antagonism by virtue of the fact that zinc is not transported by the DMT1. We also propose a shift in thinking about iron-zinc interactions from the level of enterocyte to other sites/systems in the body that may be equally relevant for the outcome and interpretation of supplementation trials. We present an overview of iron and zinc absorption and function in neural tissue as one example of possible interactions.