The RDA for zinc is 11 milligrams for men and 8 milligrams for women, and long term supplementation is safe up to at least 40 milligrams daily. The most readily absorbed forms of zinc are acetate, citrate, glycerate, monomethionine, and picolinate; in one of the few studies, zinc picolinate bested zinc citrate and zinc gluconate for absorption. Another form, zinc carnosine, has been shown to help protect gastrointestinal layers and support healthy friendly beneficial bacteria, adds Feingold. To minimize colds, it's important to take zinc in lozenge form, which allows more contact with the rhinovirus.
-Vegetarian Times Magazine, December 2015