Researchers from Wayne State University School of Medicine, Detroit, led by Dr. Ananda S. Prasad, a professor of hematology-oncology, and considered a world authority on zinc deficiency and its manifestations regarding human health, investigated the effects of zinc acetate lozenges in treating the common cold in volunteers who had cold symptoms for 24 hours or less. The study's 50 participants in this randomised, double-blind, placebo-controlled trial took either one zinc acetate lozenge containing 13.3 milligrams of zinc or an inactive "placebo" every two to three hours while awake.
The researchers reported that the average duration of cold symptoms, which included sore throat, runny nose, cough, fever and muscle aches, was about four days in the zinc group compared with seven in the placebo group. There were also shorter durations of coughing at about two versus five days, and nasal discharge at three days versus four and a half days.
56 percent of the zinc group had complete resolution of their colds after four days, whereas none of the placebo group was free of cold symptoms. A number of biochemical test results suggested that the zinc had a marked effect on colds. The investigators observed no side effects from taking the zinc supplements.
The results of previous zinc studies have been controversial. It is currently believed that zinc has no effect on preventing colds from being acquired in the first place, however this study suggests that once a cold has been caught, its effects can be lessened by taking zinc lozenges.
"Zinc acetate preparation, as used in our study, was significantly effective in decreasing the (average) duration of cold symptoms," concluded the authors. "We propose that the beneficial clinical effects seen in the zinc group were due to the antioxidant and anti-inflammatory effects of zinc."
Zinc lozenges in particular are recommended for those looking to reduce cold symptoms. The lozenge dissolves slowly in the mouth and trickles down the throat. As the common cold is usually a head cold, with the mucous membranes being the tissue most likely to be infected, sucking on a zinc lozenge allows the zinc to remain where it's needed to fight cytokines that cause the cold. In addition, the mucous membranes are thin and contain a large number of capillaries, allowing for the best zinc absorption as it dissolves.