A nutrient composition for biological systems, such as humans, animals, plants or microorganisms includes at least one monometallic or mixed-metallic phosphate of the (M1 M2 M3 . . . Mx)3(PO4)2.aH2O type where 0&nlEa&nlE9, 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.
