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Does zinc help with colds? The side effects are the surer result

Zinc may take about two and a half days off a cold, but trials disagree so much that its non-serious side effects over a week of high-dose lozenges, a third more than placebo, are rated more certain.

Zinc

Zinc is supposed to cut a cold short. Eight trials in 972 people, mixing lozenges, syrups and tablets, put the gain at about two and a half days, yet their results scatter so widely that almost none of the spread is chance. Across 16 trials, mostly a week of high-dose lozenges, non-serious side effects came about 34 percent more often on zinc, and no treatment trial recorded a serious one. How much zinc shortens a cold is still argued; that more people feel unwell on it is surer.

The findings behind this

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ImmuneZinc 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.

★☆☆Contested — the evidence disagrees with itself, or the finding carries a caution. A caution or conflict always shows one star, however strong the sources are.Conflicting evidenceEight 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.Click to keep this openSupport immunityZinc
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Physical & bodyZinc made about a third more people feel unwell than placebo did

Across 16 trials and 2,084 people, non-serious side effects came about 34% more often on zinc. That figure comes from a week of high-dose lozenges during a cold.

★★★Well replicated — this finding’s sources average out to meta-analyses, systematic reviews or high-powered trials.The figure comes from roughly a week of high-dose lozenges taken during a cold, not from a daily supplement taken for months. It counts non-serious events only, and no treatment study recorded a serious one. Sixteen trials contributed, most at unclear or high risk of bias in at least one area.Click to keep this openSupport immunityZinc

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