Daily zinc did not change your chance of catching a cold
Across nine trials and 1,449 people, daily zinc left the odds of catching a cold where it found them: anywhere from 15% fewer to 1% more.
What the study found
Taking zinc every day did not stop people catching colds
Prevention is the half of the zinc story that quietly failed. Across nine trials and 1,449 people, daily zinc left the odds of catching a cold where it found them: anywhere from 15% fewer to 1% more. The reviewers rate even that much as low certainty.
The caveat · Lozenges, syrups, gels pooled as one
Nine trials and 1,449 people, graded low certainty. The review pooled lozenges, syrups, tablets and nasal gels as one treatment, with the gluconate lozenge doses alone spanning 45 to 276 mg a day. It also excluded any product mixing zinc with other vitamins or herbs, which is most of what a pharmacy actually sells.