They”re flavored, fruity, mentholated, homeopathic, and boosted with vitamin C, mint and herbs — and they don”t work. Zinc lozenges do nothing for the common cold, according to a joint study released yesterday by physicians at Stanford University and the University of Virginia.
Despite 20 years of research, the benefits of zinc lozenges as a therapy for the common cold have not been proven, says the report, which reviewed 14 studies and found significant fault” with 10 of them.
Of the remaining four, three reported no therapeutic effect from zinc lozenges or nasal spray, and only one study found positive results from a zinc nasal gel.
“The best scientific evidence available indicates that zinc lozenges are not effective in treating colds,” summarized Dr. Jack M. Gwaltney Jr., of the Virginia campus, and one of the authors.
This is not promising news for the makers of Cold-Eeze, Zicam, Defense Health Lozenges and other products that combine a comforting little throat drop with zinc gluconate glycine — and strong claims that the combination will stave off cold symptoms.
Quigley Corp. — which manufactures Cold-Eeze — says it is “pharmacist recommended” and “clinically proven to cut colds by half,” referring customers to a 2001 study conducted at a Utah school and published in the American Journal of Therapeutics. Annual sales at the company topped $50 million last year.
The zinc factor took a darker turn when more than 400 consumers filed lawsuits against Matrixx Initiatives — makers of Zicam zinc nasal gel — last year, saying it had seriously damaged their sense of smell or taste. The company initially paid out $12 million to settle 340 claims but has taken the remaining cases to federal court.
For their research, Dr. Gwaltney and his team examined 105 medical studies probing the efficacy of zinc preparations dating back to 1984, ultimately selecting 14 placebo-controlled studies for analysis.
They found flaws in 10, including sample sizes too small to produce valid statistics, “lack of a quantifiable hypothesis” and failure to include all data and results. The shortcomings “may have invalidated the results,” the authors said.
Of the four studies that met the authors” criteria, two found zinc lozenges had no effect on the symptom severity or duration of a cold and one reported no effect of zinc nasal spray. Only one study reported a positive cold-related effect of zinc nasal gel.
“Since less information is available on the intranasal approach, additional well-designed studies of intranasal zinc spray or zinc-treated nasal swabs should be performed,” Dr. Gwaltney said.
Adults typically get three colds a year, and children up to 10.
“As the search for a cure for the common cold continues, some may be happy to learn that it isn”t contained in a zinc lozenge, as the lozenges are frequently reported to be unpleasant to the taste and may produce stomachache and nausea as side effects,” the study noted.
Taking more than 40 mg of zinc daily, however, can lead to malfunctioning of the immune system and chronic fatigue, the study said, noting that there is 5 to 24 milligrams of zinc in the lozenges, depending on the brand.