Metal chelates are complexes in which the metal atom is held through more than one point of attachment. A chelating agent which yields a soluble metal complex is a sequestering agent. Chelating agents vary in the strength with which they bind metals and in the specificity for binding various metals. The stability Constant of a chelating agent for a metal is a measure of the affinity of the metal to complex with the ligand or the chelate. The animal body contains a host of chelating agents capable of binding metals. Many plant seeds contain phosphates combined with inositol, or phytate, which may be further combined with metals such as Ca, Mg, or K. Clays, which are consumed in some cultures, have metal-binding properties and can be important in reducing the availability of trace elements which are marginally adequate in diets. Synthetic chelating agents can improve or impair the utilization of dietary minerals, depending upon their specific properties.