University of Illinois researchers found that zinc was more bioavailable when ingested as zinc methionine (OptiZinc®) than as zinc sulfate or zinc oxide. In addition, the increased bioavailability of OptiZinc® was not affected by the type of diet or level of fiber provided in the study, which is known to inhibit zinc absorption.

Source: Wedekind KJ, Hortin AE, Baker DH, Methodology for Assessing Zinc Bioavailability: Efficacy Estimates for Zinc-Methionine, Zinc Sulfate, and Zinc Oxide, Journal of Animal Science, 70:178-187, 1992.