USE OF ZINC TOLERANCE-TEST AND 24-HOUR URINARY ZINC CONTENT TO ASSESSORAL ZINC-ABSORPTION

Objectives: The sensitivity of one plasma and two urinary methods to a ssess zinc absorption after oral dosing were compared over the dose ra nge of 10 to 100 mg. Methods: Eleven healthy subjects participated in this four-way crossover design study. After an overnight fast, the sub jects received a single oral dose of zinc acetate corresponding to 10, 25, 50, or 100 mg of elemental zinc. Plasma zinc concentrations were measured at baseline (pre-zinc administration) and hourly intervals po st-zinc administration for 9 hours. Urine was collected for 24 hours p rior to and for 24 hours after zinc administration. During this 48-hou r period, subjects consumed an isocaloric, caffeine-free diet containi ng 18 mg of elemental zinc per day. Results: The area under the plasma zinc concentration versus time curve (PZAUC) increased linearly with doses between 10 and 50 mg, then flattened out. By contrast, urinary z inc excretion was approximately linear with doses in the 25 to 100 mg range, but no differences were observed in urinary zinc excretion afte r doses of 10 and 25 mg. Conclusions: Plasma zinc concentration is a u seful method of evaluating oral zinc absorption from doses of 10 to 50 mg. Urinary zinc excretion is an alternative method of assessing zinc absorption, particularly when doses of 50 to 100 mg of elemental zinc are administered.