What it's actually good for
Zinc is an essential trace mineral involved in immune cell development, wound healing, and protein synthesis. Most people eating a varied diet get adequate zinc, but vegetarians, older adults, and people with GI conditions may fall short. The strongest supplementation case is for immune support, particularly around common colds.
What the research says
Immune support and colds (Grade B). A 2013 Cochrane review found that zinc lozenges or syrup, started within 24 hours of cold symptom onset, reduced cold duration by about a day. Daily zinc supplementation supports normal immune cell function, with the most benefit seen in people with marginal zinc status. The evidence is solid but not quite Grade A because optimal dosing, form, and population vary across studies.