Tissue iron distribution and mineral excretion in rats after prolonged exposure to high levels of NaFeEDTA

Abstract

Sodium iron ethylenediaminetetraacetate (NaFeEDTA) has considerable promise as an iron fortificant in food. However, effects of administering high levels of NaFeEDTA on tissue iron distribution and mineral excretion are not well understood. The objectives of this study were to assess nonheme iron distribution in the body and urinary excretion of Ca, Mg, Cu, Fe and Zn after 21-day administration of high levels of iron in rats. Iron was given either orally with food or injected subcutaneously, as either FeSO4 or NaFeEDTA. Selected iron-containing tissues were collected for nonheme iron analysis. Estimated total body nonheme iron levels were similar in rats fed NaFeEDTA or FeSO4, but the tissue distribution was different: it was 53% lower in the liver and 86% higher in the kidneys among rats fed NaFeEDTA than among those fed FeSO4. In contrast, body nonheme iron was 2.2-fold higher in rats injected with FeSO4 than in rats injected with NaFeEDTA. Administering (fed and injected) NaFeEDTA elevated urinary Cu, Fe and Zn excretion compared with FeSO4 (1.41-, 11.9-, and 13.9-fold higher, respectively). We conclude that iron is dissociated from the EDTA complex prior to or during intestinal absorption. A portion of intact FeEDTA may be absorbed via a paracellular route at high levels of intake but is mostly excreted in the urine. Metal-free EDTA may be absorbed and cause the elevated urinary excretion of Cu and Zn.