Zinc Works, but Exerts Price in Fight Against Colds

[Guest guest]

Although zinc may be helpful in treating and preventing the common cold in

otherwise healthy individuals, the benefits come at the expense of some side

effects, a Cochrane review showed.

In an analysis of trials conducted since 1984, zinc reduced the average

duration of cold symptoms by nearly a day when taken within 24 hours of

symptom onset, and also eased symptom severity (*P*<0.05), according to

Meenu Singh, MD, and Rashmi Das, MD, of the Post Graduate Institute of

Medical Education and Research in Chandigarh, India.

In prevention trials, zinc reduced the incidence of the common cold, school

absences, and antibiotic use.

But adverse events were more frequent in the zinc groups than in the placebo

groups (56.2% versus 48.1%, *P*=0.06), a difference driven by significantly

higher rates of reports of bad taste and nausea (*P*≤0.002 for both).

" Given that some formulations (especially lozenges) produced side effects

and not all formulations may be effective, the use of zinc to treat common

cold symptoms is presently advised with caution, " Singh and Das wrote.

Schaffner, MD, chair of the department of preventive medicine at

Vanderbilt University, said in an e-mail to ABC News and *MedPage

Today*that the review consolidates what is known about zinc for the

common cold

" The good news is that zinc has some benefit, " he wrote. " If taken very

promptly, zinc seems to reduce the duration of a cold somewhat. Also, taking

zinc as a preventive measure also seems to work somewhat. Neither effect is

large, however.

" The bad news is there are side effects to zinc, " Schaffner wrote. " Also,

there are no standard zinc formulations. We still don't know what the best

dosage is. "

He said that he does not recommend zinc, but will describe the possible

benefits and side effects to interested patients.

Schaffner added that " the best treatment for a cold remains fluid,

decongestants, and time. Avoid antibiotics! "

In the U.S., the common cold results in 75 to 100 million physician visits a

year, accounting for an estimated $7.7 billion annually. Americans spend

another $2.9 billion on over-the-counter remedies and $400 million on

prescription medications for symptom relief.

In addition, colds are responsible for millions of days lost from school and

work, with cold-related work losses exceeding $20 billion a year.

Thus, Singh and Das wrote, " any medication that is only partially effective

in the treatment and prevention of the common cold could markedly reduce

morbidity and economic losses due to this illness. "

Findings from trials evaluating zinc for the treatment and prevention of the

common cold have yielded mixed results.

So the researchers examined randomized, double-blind, placebo-controlled

trials published since 1984 evaluating zinc -- in lozenge, tablet, or syrup

form -- for treatment (lasting at least five days) or prevention (with

participants taking the supplement for at least five months).

They identified 13 treatment trials including 966 participants and two

prevention trials including 394 participants. All of the trials were

conducted in high-income countries.

Overall, zinc had beneficial effects on the duration and severity of cold

symptoms.

A significantly smaller proportion of patients in the zinc group compared

with the placebo group were still symptomatic after seven days of treatment

(37.3% versus 56.3%; OR 0.45, 95% CI 0.2 to 1.00, *P*=0.05).

In the prevention trials, the rate of the common cold was reduced with zinc

from 61.8% to 38.2% (*P*=0.006). The average length of school absence was

reduced by an average of 0.37 days, and fewer patients taking zinc received

a prescription for antibiotics (12.7% versus 33%).

The researchers described the quality of the evidence as moderate

(indicating that further research may change the estimate) for the analyses

of duration, severity, and incidence, and as low or very low for the other

outcomes.

Although zinc appears to be useful in treating or preventing the common

cold, the mechanisms underlying the benefits remain unclear, according to

Singh and Das.

Possibilities include an interaction of zinc with the host's immune

function, direct inhibition of viral replication, and a blocking of

receptors on the nasal epithelium occupied by rhinoviruses during a cold.

But even with the potential benefits, the researchers wrote, " the higher

incidence of side effects in zinc-treated participants will most likely

limit the usefulness of zinc in the treatment of cold symptoms.

*Primary source: *The Cochrane Library

Source reference:

Singh M, Das R " Zinc for the common cold " *Cochrane Database Syst Rev* 2011;

DOI: 10.1002/14651858.CD001364.pub3.

link <http://www.medpagetoday.com/Pulmonology/URIstheFlu/24892>

--

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