This story discusses the results of a systematic review from the Cochrane Collaboration suggesting that zinc reduces the duration and severity of the common cold. While the column does a nice job of pointing out some of the limitations of the studies included in the review and highlights the fact the review authors cannot make a recommendation for the dosage or preparation, it missed the mark on a few key points. For instance, there was no discussion of costs, (which seems like an important omission, as many readers will want to try the over-the-counter products), there was little mention of the adverse effects of zinc, and there was no commentary from an independent expert.
Although most of us view the common cold as a mere nuisance, the infection can have serious clinical and economic impact. The common cold is responsible for a large number of lost work days, lost school days and physician visits. Over $400 million is spent annually in the US for over-the-counter remedies. Unfortunately, the common cold is also responsible for significant number of prescriptions for antibiotics despite the fact that antibiotics do not work against viral infections. The common cold can also trigger ear infections, sinusitis and worsen lung disease. The Cochrane review of published studies assessing the value of a number of different zinc products as both preventives and for treatment provides a new look at a long standing question: Do zinc salts provide any benefit in the treatment or prevention of the common cold?
Although researchers have not reached a consensus about the optimal dose or formulation, the story could have provided cost information for the various over-the-counter zinc products. In addition, this story could have been enhanced by a brief discussion of the general costs of treatment and the cost of lost work days, school absenteeism, and physician visits.
The story indicates that when zinc is taken within the first 24 hours of developing cold symptoms, it cuts the duration of a cold by an average of 1 day. No data from the review were provided regarding other outcomes, such as severity of symptoms, reduced absences from school, and reduced antibiotic use. Also, the story should have noted that a preventive effect was found after 5 months of zinc use and people who experienced a therapeutic benefit took zinc for at least 5 days during their cold.
The story pointed out that nasal zinc products, associated with loss of smell, were not evaluated in the Cochrane review and it quotes one of the authors of the study suggesting that the potential harms of zinc products are limited to a bad taste and some nausea. However, the full listing includes constipation, diarrhea, abdominal pain, dry mouth and oral irritation.
While the story did a nice job of explaining some of the limitations of the studies included in the systematic review, particularly the issue of not adequately blinding participants to their assigned treatment, it failed to mention a few important points. For example, trial participants were between the age of 1 and 65 years and were in good health; therefore, the results may not apply to the elderly or those who have underlying illnesses. Also, the story is somewhat misleading in how the data was evaluated. While the review included 15 studies with a combined 1,360 participants, it would have been useful to note that 13 trials (966 participants) analyzed the therapeutic benefit for zinc, while 2 trials (394 participants) evaluated its preventive effect. Furthermore, not all the trial results could be pooled due to the nonstandarized approach to reporting outcomes. The story should have also noted that the authors had a good deal of confidence in the conclusions drawn about the duration of sickness and severity of symptoms, but they were far less confident in the other outcomes, such as prevention, fewer school absences, and less antibiotic use. The story places equal credence in the ability of zinc to influence all of these outcomes.
The story did not engage in disease-mongering. And while we recognize that the majority of readers are familiar with the common cold, we would have liked to have seen some information on the estimated number of cases of the common cold, days out of work or other estimates to put the story into perspective.
The story includes commentary from the review’s lead author, as well as Dr. Prasad, “an early pioneer of research into zinc as an essential mineral.” Two of Dr. Prasad’s many articles were included in the Cochrane Review. Quotes from an independent expert would have been welcomed.
While the review only includes trials comparing zinc to a placebo, the story could have briefly discussed the efficacy of other types of over-the-counter cold remedies. Furthermore, we would have liked to have seen some comment on the best ways to protect yourself and your family from getting a cold besides zinc products. A few words about hand hygiene and keeping your hands away from your eyes, mouth, and nose would have been helpful to readers.
There is no question regarding the availability of products containing zinc; however, as the writer points out, the most effective formulation and dosage for reducing cold symptoms is currently unknown.
Of note, the story specifically mentions that zinc lozenges from Coldcure.com were used in many of the trials evaluated in the Cochrane systematic review, but failed to note that they are no longer manufactured.
The story makes it clear that the first trial evaluating the efficacy of zinc for treating symptoms of the common cold was published in 1984.
This story does not appear to rely on a news release.