Zinc

Research summary

• An updated Cochrane review found zinc can reduce the duration of common cold symptoms when started within 24 hours of onset, a finding consistent with an earlier Cochrane review and supportive systematic reviews, though the benefit is modest and dosing/formulation dependent.
• In eye health, the landmark AREDS randomized trial found high-dose zinc combined with antioxidant vitamins reduced progression to advanced age-related macular degeneration in at-risk patients — one of the more definitive supplement trials in ophthalmology.
• For metabolic health, multiple meta-analyses find zinc supplementation modestly improves lipid profiles and glycemic control in people with type 2 diabetes, with one study triangulating evidence from both a randomized trial and Mendelian randomization to support a causal glycemic benefit.
• As with several supplements here, zinc's effects are real but specific and modest rather than broadly protective.