All the evidence for the three-day claim comes from 199 people
Every zinc acetate lozenge trial ever run pools to 199 patients and a cold about three days shorter than the usual seven. Two of the three came from one group.
What the study found
The three-day figure rests on 199 patients and one group
Every zinc acetate lozenge trial ever run pools to 199 patients and a cold about three days shorter than the usual seven. The trial anchoring it treated 50 people. Two of the three came from one research group, and the pooled analysis has a co-author working for a lozenge developer.
The caveat · Trial and pooled result overlap
Fifty people in the primary trial, which reported colds 44% shorter, far above anything the wider literature supports. That trial is one of the three inside the pooled analysis, so the two are not independent confirmations of each other. The finding that the effect held regardless of allergy, smoking, age or gender rests on those same 199 people, too few for that comparison to carry weight.
What we don't know
Fifty people in the primary trial, which reported colds 44% shorter, far above anything the wider literature supports. That trial is one of the three inside the pooled analysis, so the two are not independent confirmations of each other. The finding that the effect held regardless of allergy, smoking, age or gender rests on those same 199 people, too few for that comparison to carry weight.