The present invention relates to a method for the preparation of biologically active amorphous calcium carbonate (ACC)-polyphosphate microparticles. The method comprises preparing an aqueous solution of a polyphosphate salt (polyP) in about 0.1M sodium hydroxide； adding about 0.5mol/L of sodium carbonate； diluting the resulting solution with about 1.5 volumes of deionized water； and mixing the solution with the same volume of an aqueous solution containing calcium chloride such that an about equimolar concentration ratio between calcium ions and carbonate ions results. The mixture is then washed with a lower alkyl ketone at about room temperature, followed by filtering and drying of a precipitate as formed. Preferably the polyphosphate salt is sodium polyphosphate (Na-polyP). Also claimed is an implant material produced by the method, preferably an artificial bone implant. The polyphosphate is thought to block the transformation of the metastable ACC into the most stable crystalline calcium carbonate polymorph. This stabilized ACC composition is claimed to be used as a food or dietary supplement, for use in the treatment of calcium deficiency and for use in the prophylaxis and/or therapy of osteoporosis.
