For the cold virus,zinc may edge out even chicken soup

In some of the cited studies,the benefits of zinc were significant. A March 2008 report in The Journal of Infectious Diseases,for example,found that zinc lozenges cut the duration of colds to four days from seven days,and reduced coughing to two days from five.

While the findings are certain to send droves of miserable cold sufferers to the drugstore in search of zinc treatments,the study authors offered no guidance on what type of zinc product to buy. The authors declined to make recommendations about the optimal dose,formulation or duration of zinc use,saying that more work was needed before they could make recommendations.

“Over all,it appears that zinc does have an effect in controlling the common cold,” said Meenu Singh,the review’s lead author and a professor in the department of paediatrics at the Postgraduate Institute of Medical Education and Research in Chandigarh. “But there still needs to be consensus about the dose.”

Zinc experts say that many over-the-counter zinc products may not be as effective as those studied by researchers because commercial lozenges and syrups are often made with different formulations of zinc and various flavours and binders that can alter the effectiveness of the treatment.

“A lot of preparations have added so many things that they aren’t releasing zinc properly,” said Ananda Prasad,professor in the department of oncology at Wayne State University School of Medicine in Detroit and an early pioneer of research into zinc as an essential mineral. Two of Prasad’s studies were included in the Cochrane report.

“The public is confused because people have used the wrong dose,they have used the wrong sort of zinc or they have not started the treatment within 24 hours of onset,” he said.

Even so,the new report gives credence to the long-debated theory that zinc can be an effective treatment for colds. While it’s not certain how the mineral curbs colds,it appears to have antiviral properties that prevent the cold virus from replicating or attaching to nasal membranes.

The studies used various forms and doses of zinc,including zinc gluconate or zinc acetate lozenges and zinc sulphate syrup,and the dose ranged from 30 to 160 mg a day. Prasad said his studies have used zinc acetate lozenges that contained about 13 milligrams of zinc. Study participants took a lozenge every three to four hours during the day for four consecutive days,resulting in a daily dose of 50 to 65 mg a day,he said.

Some cold sufferers have been wary about using zinc since the Food and Drug Administration warned consumers to stop using Zicam nasal sprays and swabs,which contain zinc,after numerous reports that some users lost their sense of smell after using the product. TARA PARKER-POPE