Effects of Initiation and Discontinuation of Short Term Zinc Supplementation on Plasma Zinc Concentration

This is a double-blind, randomized controlled trial conducted in men 19-65 years of age who will receive daily zinc supplements (10 or 20 mg zinc/d as zinc sulfate) or placebo for 21 days. Blood samples for plasma zinc and CRP concentrations will be drawn at baseline and days 1, 2, 5, 9, 14, and 21 during supplementation and days 1, 2, 5, 9, and 14 after discontinuation of supplementation.

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.

• Dietary Supplement: zinc sulfate
  20 or 10 mg zinc per day for 3 weeks
  Other Name: Producer: UCD pharmacy
• Dietary Supplement: Placebo
  Daily placebo for 3 weeks
  Other Name: Producer: UCD pharmacy

• Experimental: Zinc supplement (20 mg)
  Daily intake of 20 mg supplementary zinc
  Intervention: Dietary Supplement: zinc sulfate
• Experimental: Zinc supplement (10 mg)
  Daily intake of 10 mg supplementary zinc
  Intervention: Dietary Supplement: zinc sulfate
• Placebo Comparator: Placebo supplement
  Daily intake of placebo supplement
  Intervention: Dietary Supplement: Placebo

Inclusion Criteria:

• Generally health men
• 19-65 years
• Non-anemic

Exclusion Criteria:

• Age <19 or >65
• Hemoglobin <120 g/L
• Clinical evidence of illness
• Consumption of mineral supplements
• Recent blood donation (within 8 weeks)