Studies disagree — unsettled
A 2024 Cochrane review found zinc barely prevents a cold at all, but may shorten one already underway by about two days — with more side effects than placebo either way.
A 2013 genome-wide study of two adult cohorts (Australian twins and families, UK pregnant women) found three loci for blood zinc, measured directly in red blood cells. The strongest, at 15q24.2 near PPCDC and SCAMP5 (rs2120019), reached p = 2 × 10⁻¹⁸. The same study also found loci for blood copper and confirmed one for selenium — this site's selenium page covers a separate, larger selenium-specific meta-analysis instead.
Zinc's best-known everyday use is the common cold. A 2024 Cochrane review of 34 trials and 8,526 participants found little or no reduction in the risk of catching a cold (risk ratio 0.93, 95% CI 0.85–1.01, low-certainty evidence). But when zinc — usually as a lozenge — was given after a cold had already started, it may have shortened its duration by about 2.37 days (95% CI 4.21 fewer to 0.53 fewer, low-certainty evidence), alongside a probable increase in non-serious side effects such as bad taste, nausea and mouth irritation (risk ratio 1.34, 95% CI 1.15–1.55). The review's own conclusion is a genuine split: little help preventing a cold, possible but uncertain help shortening one, with more side effects either way.
Zinc is also one of the minerals in the AREDS2 eye formula, where a much-discussed claim that CFH genotype should redirect zinc dosing did not hold up under independent re-analysis — covered on that page.
No genotype changes any of this. Blood zinc is measured directly when it matters clinically, and the decision to try zinc for a cold already underway is the same one for everyone: a modest, uncertain benefit against a real chance of an upset stomach or a bad taste in the mouth.
Zinc is a trace mineral involved in immune function and wound healing, obtained from meat, shellfish and legumes. Zinc is commonly taken at the first sign of a cold, on the theory that it shortens the illness.
Not reliably — a 2024 Cochrane review of 34 trials found little or no reduction in the risk of catching a cold.
It may — about 2.37 days shorter on average in the same review, though the evidence is low-certainty and comes with more non-serious side effects such as bad taste and nausea.
No. It marks a real, replicated locus for blood zinc levels, but no guideline sets an intake target from it — blood zinc is measured directly when it matters clinically.
Related but distinct. The AREDS2 page covers a debunked claim that CFH genotype should change zinc dosing in an eye-health formula; this page covers zinc's genetics and its much more common everyday use, the common cold.
Nothing on this page recommends taking anything. If a result here matters to you, take it to a doctor or a pharmacist rather than to a shop.