A dietary source of mineral in the form of a metal carboxylate is prepared using the acid-base-like reaction. A salt of a carboxylate anion and a by-product cation is reacted in aqueous solution with a salt of a metal cation and a by-product anion under conditions which form a metal carboxylate and the by-product salt. Solutions formed in the reaction may be applied directly to a dry carrier to produce a dry dietary supplement or, alternatively, the solutions may be filtered to remove precipitated by-product salt and the filtrate used as a liquid dietary supplement. Preferably, a reducing agent, such as ascorbic acid, is added to help prevent the oxidation of divalent to trivalent form of a metal salt, when an easily oxidized divalent metal is used as starting material.