Neither the zinc form nor a doubled dose changed much
Zinc acetate beat placebo by 40% and gluconate by 28%, a gap whose range still includes gluconate ahead. Going from roughly 90 mg a day to roughly 200 moved it two points.
What the study found
Doubling the lozenge dose bought two percentage points
The two claims the lozenge market runs on both failed their direct test. Zinc acetate beat placebo by 40% and gluconate by 28%, a gap whose range still includes gluconate coming out ahead. Going from roughly 90 mg of zinc a day to roughly 200 moved the answer by two points.
The caveat · Tiny groups could hide a real gap
These are null results in very small groups: three acetate trials against four gluconate ones, and five lower-dose trials against two higher-dose. Failing to show a difference in 575 people is not the same as showing there is none, and the ranges are wide enough to hide a real one in either direction. Every trial used lozenges in adults with ordinary colds, so none of it reaches children, prevention, or any other route.