A nutrient composition for biological systems, such as humans, animals, plants and microorganisms, which comprises at least one monometallic or mixed-metallic phosphate of the (M1 M2 М3…Мх)3(РО4)2 · а Н2О type where 0 ≤ a ≤ 9, where (M1, M2, M3… Mx) represent the one metal of the monometallic phosphate or the two or more metals of the mixed-metallic phosphate and are selected from Na, K, Mg, Ca, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, Zn and B, with the proviso that at least one of the metals in the phosphate is selected from Mn, Fe, Co and Ni, the at lest one phosphate being preparable or having been prepared by a) preparing an aqueous solution (I) comprising at least one or more than one of the metals Mn, Fe, Co and/or Ni as divalent cations, by introducing oxidic metаl(II), metal(III) and/or metal(IV) compounds or mixtures or compounds thereof having mixed oxidation states, selected from hydroxides, oxides, oxide hydroxides, oxide hydrates, carbonates and hydroxide carbonates, of at least one of the metals Mn, Fe, Co and/or Ni together with the elemental forms or alloys of at least one of the metals Mn, Fe, Co and/or Ni, into an aqueous medium comprising phosphoric acid, and reacting the oxidic metal compounds with the elemental forms or alloys of the metals (in a redox reaction) to give the divalent metal ions, b) removing any solids present from the aqueous phosphoric acid solution (I), c) if the phosphate is a mixed-metallic phosphate and, in addition to the metals introduced into the solution in stage a), comprises further metals selected from (M1, M2, M3… Mx), at least one compound of at least one of the metals (M1, M2, M3… Mx) is additionally added to the aqueous solution (I) in the form of an aqueous solution or as a solid in the form of a salt, the at least one compound preferably being selected from hydroxides, oxides, oxide hydroxides, oxide hydrates, carbonates, hydroxide carbonates, carboxylates, sulfates, chlorides or nitrates of the metals, d) providing an i
