A new study has rekindled the debate over how effective zinc can be in preventing and treating the common cold.
In the recent research from the University of Helsinki, scientists said people who took a relatively high dose of zinc daily had a rate of recovery that was three times better than people who didn’t take the chemical element.
Infectious disease experts interviewed by Healthline had mixed opinions on these findings.
One expert noted the inconclusive, and sometimes contradictory, results from past studies, as well as the high dosage given to people in this experiment.
“I would take the results with a grain of salt,” said Dr. Pritish Tosh, an infectious disease specialist at the Mayo Clinic in Minnesota.
Others noted the success in the study as well as the lack of side effects.
“It doesn’t appear to do any harm and there really isn’t any other good options,” said Dr. Hilary Hawkins, a family medicine physician at Orlando Health in Florida.
What the researchers found
In their study, the Helsinki researchers did a meta-analysis of three randomly controlled trials involving zinc acetate lozenges.
The patients in those studies took 80-92 milligrams of zinc per day after the onset of cold symptoms.
Those doses are significantly higher than the recommended daily doses in the United States of 11 mg for men and 8 mg for women.
However, the researchers noted that in other studies participants have been given daily doses of 100-150 mg for months without serious side effects.
They said in their analysis 70 percent of people who took zinc had recovered from their cold after five days compared with 27 percent of the participants who were given a placebo.
They added the zinc lozenges were effective in people regardless of their age, gender, race, allergies, or cold severity.
They also noted that most lozenges sold over the counter do not contain the levels of zinc used in these studies.
The researchers said further studies should be done on the best formula for zinc lozenges, as well as the optimum frequency of taking the medication.
“Given the strong evidence of efficacy and the low risk of adverse effects, common cold patients may already be encouraged to try zinc acetate lozenges not exceeding 100 mg of elemental zinc per day for treating their colds,” said Dr. Harri Hemila, from the University of Helsinki in Finland.
Are the claims valid?
Tosh is a bit skeptical of the meta-analysis.
He said zinc has been studied as a remedy for colds for a long time, and the results are varied.
He also noted that the high doses of zinc might be effective in the short run, but he would be concerned about some of the long-term toxicity.
He told Healthline that rest and hydration are still the main remedies for a cold.
“Taking zinc shouldn’t be done in lieu of taking care of yourself,” he said.
Hawkins agreed that one analysis isn’t enough to formulate concrete conclusions.
“This is a compelling study and it warrants further study,” she told Healthline. “However, one study is one study.”
She also noted that there are different strains of cold viruses that make the ailment tough to treat.
“There really isn’t one good medicine for them,” she said.
Hawkins did say she would recommend people with a cold consider trying zinc lozenges as long as they didn’t have any side effects or mind the sometimes metallic taste.
She said zinc is known to have antiviral effects similar to the anti-bacterial effects of silver.
Dr. William Schaffner, an infectious disease specialist at the Vanderbilt University Medical Center in Tennessee, thinks along the same lines.
He noted the inconsistency of past studies, but also observed that zinc seems to produce few side effects.
He said it appears if a person with a cold takes a high enough dose of zinc, they will “get better a little faster.”
He cautioned that the lozenges are not regulated by the Food and Drug Administration (FDA), so the effectiveness may vary.
He also told Healthline there needs to be more study on what the proper dosage should be, how often the lozenges should be taken, and if they should be administered before cold symptoms appear or afterward.
“Common colds are a vexing problem,” he noted.
Because of that, he said further research is a worthy endeavor.
“It would be nice if we had a safe, reliable, inexpensive remedy,” he said.