A method of providing zinc to a subject in need of treatment includes administering to the subject an effective amount of a zinc-cysteine complex. The zinc-cysteine complex is preferably a zinc-monocysteine complex. The complexes of zinc-cysteine of the present invention increase the activity of antioxidant enzymes catalase and glutathione peroxidase, and the antioxidant protein metallothionein. The complexes of zinc-cysteine of the present invention protect retinal pigment epithelial cells from increasing hydrogen peroxide concentrations.
