Common Cold Tests Zinc's Mettle

Research divided on whether the element shortens symptoms

SUNDAY, Dec. 8, 2002 (HealthDayNews) -- Sniffling again?

Perhaps you should try zinc supplements, which have been shown in certain trials to cut the duration of a cold in half. Some researchers have even heralded the element as the long-sought "silver bullet" for treating the common cold.

But, does it actually work?

"It depends on who you ask," says Dr. Sherif Mossad of the Cleveland Clinic in Ohio. "The weight of the data is equal in both directions."

Over the past decade, about 14 studies have been done on the mineral's cold-curing power. According to Mossad, half have shown that it works and half that it doesn't.

"I don't think the pendulum is going one way or the other at this time," he says. "Every year, one or two studies come out because the cold is such a common problem."

An estimated 62 million people develop colds in the United States annually, according to the U.S. Centers for Disease Control and Prevention.

Children have about six to eight colds a year. In families with children in school, the number of colds per child can be as high as 12 a year.

Adults average two to four colds a year. And women, especially those 20 to 30 years of age, have more colds than men, possibly because of their closer contact with children, the National Institute of Allergy and Infectious Diseases says.

While health authorities know a lot about who gets colds and how frequently, it's much more difficult to nail down the strain of cold and its symptoms.

Colds are caused by viruses, and researchers estimate that about 200 of them circulate during the cold season, which runs from November to April. So determining the type of cold a person has and what it will do is nearly impossible, Mossad says.

Another limiting factor to studying the common cold is the wide variety of symptoms associated with it, and the subjective evaluation of them. When scientists analyze the effectiveness of a cold treatment, they depend on patients' reports about how they feel, which can alter results from study to study.

"With this illness, you have mainly subjective responses to the medicine. It's not like you give a person a blood test and you can see a change," Mossad says.

All that said, however, zinc appears to be one of the most effective cold treatments available. The element is usually taken as a lozenge or nasal spray. Scientists believe it works by either preventing virus cells from reproducing or coating them so they can't take effect in the body.

Six years ago, Mossad conducted a randomized, double-blind, placebo-controlled study of zinc's ability to cure the cold in 100 adults. The patients who received zinc lozenges six or eight times a day felt relief nearly twice as fast as those using a placebo lozenge. They saw their symptoms disappear after an average of 4.4 days, compared to 7.6 days for the placebo group. The difference was most apparent with coughing and sore throat.

Mossad's best evidence, though, may be the element's work on his own stuffy head.

"Personally, I use it when I have a cold and I seem to get better quicker," he says.

Other studies, however, cast doubts.

Four years ago, a prominent trial of school children showed that zinc did little to assuage their symptoms. Researchers reported in the Journal of the American Medical Association that they tested 250 children outside Cleveland, and found that both those taking zinc lozenges and those taking a placebo suffered symptoms for an average of nine days.

Moreover a "meta-study" in the Journal of Nutrition two years ago, which evaluated 11 studies, found that zinc's effectiveness in curing the cold still hasn't been proven. Many of the positive studies suffered methodological failings, such as using an ineffective placebo lozenge, researchers say.

However, the studies concluding zinc doesn't work also suffer from problems, says Dr. Ananda Prasad, a professor of medicine at Wayne State University in Detroit. They failed, he argues, because scientists used lozenges that included elements besides zinc, because they used doses that were too small, or because they started treatment more than 24 hours after the cold began.

"It is really very disturbing. This is not fair for the public," he says. "Most of the confusion is that people have been using the wrong preparations of zinc. Many don't work."

Prasad recommends that people use simple zinc lozenges without added ingredients or flavorings. Even though such lozenges have a poor taste and can cause nausea on an empty stomach, they work much better, he says. His study in 2000 also showed that zinc cut the duration of a cold in half.

"I have no question in my mind that zinc works. We have used it a lot here at the medical center. But we always use the right kind, so it works," he says.

For the lozenges to work, they should be taken every two or three hours, in 12 milligram to 13 milligram doses, he says.

Since too much zinc can reduce the copper level in the body, hurting immune response, people shouldn't take high doses of the element for longer than four days, Prasad says.

What To Do

For more information about the cold virus, visit the Common Cold Centre, run by Cardiff University in South East Wales, Britain. Or read more about the cold at the National Library of Medicine.

SOURCES: Sherif Mossad, M.D., Cleveland Clinic, Cleveland; Ananda Prasad, M.D., Ph.D., distinguished professor, medicine, Wayne State University, Detroit; June 1998 Journal of the American Medical Association; May 2000 Journal of Nutrition
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