This multi-center study aims to determine the pharmacokinetics and pharmacodynamics of a novel gastro-retentive, sustained-release zinc cysteine preparation on the blood and urine measures of copper and zinc balance in Alzheimer's disease and mild cognitive impairment. Data expected to be derived include tolerability of the novel preparation in comparison with oral inorganic zinc salt, and long-term effects on primarily blood-measured copper-zinc balance. The study design is that of a prospective, randomized, double blind placebo-controlled clinical trial, with a duration for individual subjects of 6 months. The study will be performed at a total of 3 sites, under the direction of a single principal investigator, with a sub-investigator. The statistical plan calls for a comparison of data from the two long-term parallel groups using ANOVA and other applicable techniques. In addition to blood parameters, mental function assessments obtained at baseline, 3 and 6 months will be evaluated statistically.