People who take oral zinc may experience shorter common cold symptoms than those who do not, researchers from The Hospital for Sick Children (SickKids), Toronto, and McMaster University reported in CMAJ (Canadian Medical Association Journal).The authors added that adverse effects, especially when higher doses are taken, are common.

The authors gathered data on 17 randomized human studies involving 2,121 individuals aged from 1 to 65 years. They wanted to find out how efficient and safe oral zinc might be as a treatment for the common cold. All the trials used placebos and oral zinc preparations, and were double-blinded.

They found that zinc significantly reduced cold symptom duration, compared to placebos. However, they emphasized that the evidence was of “moderate” quality. Higher doses appeared to have a better effect.

Dr. Michelle Science said:

“We found that orally administered zinc shortened the duration of cold symptoms. These findings, however, are tempered by significant heterogeneity and quality of evidence.”

After taking oral zinc supplements for one week, the evidence or any benefits regarding cold symptoms was week. Taking zinc for two to three days seemed to have no impact at all.

Regular zinc consumption was found to help adults reduce their duration and severity of cold symptoms. However, no benefits at all were observed in children.

The most common adverse events associated with zinc supplements were nausea and a bad taste.

Dr. Science explained that prior studies showed conflicting effects of zinc in the reduction of symptom severity, as well as duration.

The authors concluded:

“Until further evidence becomes available, there is only a weak rationale for physicians to recommend zinc for the treatment of the common cold. The questionable benefits must be balanced against the potential adverse effects.”

Written by Christian Nordqvist