Effects of Initiation and Discontinuation of Short Term Zinc Supplementation on the Magnitude and Velocity of Change in Plasma Zinc Concentration

The study will be a double blind, randomized, placebo controlled trial conducted in men 19-65 years of age. Participants will receive daily zinc or placebo liquid supplements for 21 days. Supplemental zinc will be given as zinc sulfate; the lower dose zinc supplement will contain 10 mg/d elemental zinc, and the higher dose zinc supplement will contain 20 mg/d elemental zinc. The placebo will contain the same excipients expect for zinc sulfate.

Multiple blood draws will be performed throughout the course of the study, to determine the responsiveness of plasma zinc concentrations to zinc supplementation. Two baseline blood draws will occur prior to the start of supplementation (study days -7 and 0). Blood draws will be performed on days 1, 2, 5, 9, 14 and 21 of the 21 day supplementation period. Upon termination of supplementation (day 21), blood draws will be performed on days 1, 2, 5, 9, 14 and 21 post-supplementation (study days 22, 23, 26, 30, 35 and 42).

The major outcomes of interest are the magnitude and velocity of change in plasma zinc concentration. Other outcomes to be assessed are plasma concentrations of the acute phase proteins CRP and AGP, as well as reported morbidity, because of their potential roles as confounding variables. Anthropometric variables will be assessed at baseline.