Since the 1980s, zinc supplements have been marketed with claims of effectiveness against colds. Zinc is an essential mineral naturally present in many foods and plays a role in immune function. Researchers note that zinc intake in the general population, via diet, is generally sufficient, however, aging and certain chronic illnesses can lead to a deficiency.
The theory that zinc can interfere with viral replication when it comes into contact with viral particles present in the nose, mouth and throat has been well demonstrated in vitro, and in vivo in mice, but this advantage remains yet to be demonstrated in humans.
2 fewer days of colds, but mild side effects
The study therefore tests whether zinc is useful for preventing or treating a cold through the review and meta-analysis of 19 clinical trials of zinc as a treatment for the common cold, and 15 trials of zinc as a preventative measure. These trials presented numerous variations both in doses, modes and durations of quantity administration but also in the very clinical definition of the common cold, note the researchers. The analysis finds that:
- 8 studies involving a total of 972 participants used zinc as a treatment to reduce the duration of colds. Combined, their results provide low-certainty evidence that zinc supplementation may help reduce the duration of a cold by about 2 daysvs placebo;
- there is no strong evidence to conclude that zinc has any impact on the severity of cold symptoms;
- trials that have focused on zinc for prophylaxis provide no clear evidence of the benefit of taking zinc before the onset of a cold;
- However, some side effects are reported, which include intestinal disturbances, nausea and an unpleasant taste. However no serious side effects have been identified.
“Thus, doctors who prescribe zinc to treat a cold should be aware of the limited evidence and possible side effects”concludes Dr. Daryl Nault of the University of Maryland, lead author of the analysis. “Ultimately, it is up to the patient to decide whether the risk of unpleasant side effects is worth the benefit of “potentially” shortening their symptoms, and by a few days.”
Thus, the evidence for the effectiveness of zinc against the common cold is far from established. Additional studies investigating the most promising types and doses of zinc products using appropriate methodologies will allow check if zinc can have a place in the treatment of colds.
