In vitro dialyzability of zinc from different salts used in the supplementation of infant formulas.

Seven zinc salts--acetate, chloride, lactate, sulfate, citrate, gluconate, and oxide--were added to milk--and soy-based infant formulas to estimate possible differences in zinc availability depending on the type of salt used. For this purpose, an in vitro method that estimates the dialyzability of the element (i.e., the fraction available for absorption) was applied. Zinc dialyzability is always higher in milk-based products than in soy products, even when the total zinc contents are higher in the latter. The salts can be classified according to the zinc dialyzability in the two types of formulas as follows: oxide > gluconate = chloride = lactate > citrate = acetate > sulfate. Therefore, according to the dialysis percentage, oxide and gluconate are the compounds of choice for zinc supplementation of infant formulas.