Dietary Factors That Affect Biological Availability of Trace Elements

There are numerous dietary factors that affect the biological availability of trace elements (Cr, Mn, Fe, Co, Cu, Zn). Notable among these factors are solubility, adsorption and complexation with natural or synthetic chelating agents. Recently, the significance of chelation in promotion or inhibition of absorption has become widely recognized. The stability and solubility of trace metal complexes either present in the diet or formed in the gastrointestinal tract are important determinants in the absorption fate of a complexed ion. If the chelate is much more stable than the complex formed with specific proteins at the absorption site, or if the complex is insoluble, the ion will not be efficiently absorbed. If the complex is soluble and less stable than the absorption site complexes, it may promote absorption, particularly if an insoluble compound results from interaction of the ion with a competing chelating agent. Phytate forms insoluble complexes with iron and zinc and decreases their absorption. In the case of zinc, chelating agents such as EDTA and certain amino acids counteract the phytate effect. 41 references, 4 figures, 4 tables.