Zinc may shorten a cold, on trials that barely agree with each other
The current estimate is about two and a half days off a cold. It comes from eight trials whose results scatter so widely that almost none of the spread is chance.
What the study found
Zinc may cut a cold short, on trials that barely agree
The current estimate is about two and a half days off a cold, and it arrives with a warning. Eight trials produced it, and their results scatter so widely that almost none of the spread is chance. The reviewers rate the rise in side effects as more certain than the benefit.
The caveat · Mixes three zinc forms
Eight trials, 972 people. The estimate mixes zinc acetate, gluconate and orotate given as lozenges, syrups and tablets, so it is an average over treatments that may not behave alike. Most of the included studies carried an unclear or high risk of bias in at least one area.
What we don't know
Zinc lozenge trials scatter widely. One reading says that makes any effect size untrustworthy; another sees a dose split, nothing below about 75 mg a day and a great deal above. No trial has split them, so how much zinc helps is open.