‘Limited evidence’ that zinc can prevent, treat cold symptoms

Is it time to rethink zinc?

New research has found that taking zinc may help shorten the length of a person’s cold by about two days — but the evidence isn’t definitive and it may not be worth the side effects.

A healthy diet can easily provide enough zinc, which is found in foods such as red meat, cashews and oysters. The essential mineral is also available in over-the-counter supplements — zinc lozenges have long been used for cold symptoms, despite uncertainty surrounding their overall effectiveness.

Zinc plays a key role in supporting our immune system, with research suggesting it may interfere with the binding and replication of viruses involved in colds.

But an analysis of 34 studies about zinc, published Wednesday in the Cochrane Database of Systematic Reviews, reports that taking it “may make little to no difference” in preventing or treating a cold.

Eight of the studies, involving a total of 972 participants, provided “low-certainty evidence” that zinc may help reduce a cold by around two days compared to the average weeklong duration for the people who took a placebo.

Still, those who took zinc for their cold reported side effects such as an unpleasant taste, nausea and bowel problems — nothing too severe.

“People considering zinc to treat a cold should be aware of the limited evidence base and possible side-effects,” said assistant professor Daryl Nault of Maryland University of Integrative Health, first author of the review. “Ultimately, it’s up to the individual to decide whether the risk of potential unpleasant side-effects is worth the benefit of potentially shortening their illness by a few days.”

The study authors say more research is needed since the trials they included in the review varied by the type and dosage of zinc taken, the way it was administered and the process for reporting how the cold was resolved.

Few studies monitored specific symptoms, the researchers noted.

“The evidence on zinc is far from settled: we need more research before we can be confident in its effects,” said assistant professor Susan Wieland of the University of Maryland School of Medicine, senior author of the review.