From The November 2000 Issue of Nutrition Science News
Zinc lozenges have been used to treat the common cold for a number of years, but research results on their effectiveness have been contradictory. Now, a comprehensive, randomized, double-blind, placebo-controlled trial conducted by Ananda Prasad, M.D., Ph.D., of Wayne State University in Detroit has shown that zinc lozenges work.
Forty-eight students, staff and employees at Wayne State University who had cold symptoms for 24 hours or less were given either a placebo or a zinc lozenge that contained 12.8 mg zinc acetate. Participants were given 50 lozenges and asked to dissolve one in their mouths every two to three hours while awake as long as they had cold symptoms. They took no other cold preparations. All participants returned to the clinic one day after their colds ended. At that time, their plasma was examined for an immune factor called pro-inflammatory cytokines, which causes cold symptoms.
The zinc recipients suffered from their colds an average of 4.5 days, whereas the placebo group was under the weather an average of 8.1 days. Most notably, zinc recipients coughed for only three days compared to six days for the placebo patients. When they initially came in for treatment, those who ended up taking zinc supplements actually reported more severe cold symptoms, including fever, sneezing and sore throat. However, by day four, their severity score was only half that of the placebo group.
The participants given the zinc lozenges ingested approximately 80 mg of elemental zinc per day for about five days—five times the recommended daily allowance. The researchers recommend that this zinc dose not be sustained for many weeks at a time because it could cause copper deficiency, but they say it is safe to take during the shorter duration of a cold. Although researchers suggested the improvement in clinical symptoms might be caused by a reduction in immune cytokines, actual plasma cytokine levels were not significantly different between the two groups, possibly because blood samples were taken too long after the end of the colds.
Duration of Symptoms and Plasma Cytokine Levels in Patients with the Common Cold Treated with Zinc Acetate: A Randomized, Double-blind, Placebo-controlled Trial