How strong is the evidence for Zinc?

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. That evidence is currently rated moderate (60/100), built on 10 published studies, including 1 randomized controlled trial and 7 meta-analyses -- a reasonable base, but not yet enough for full certainty.