1. Zinc. The mineral zinc, available in over-the-counter lozenges, nasal sprays, and gels, are said to work by preventing the formation of proteins needed by a cold virus to reproduce.



Despite all the claims about zinc for treatment of a common cold, scientific studies are scarce. It's said that only 14 published studies that looked at zinc the scientific way, with both placebo and treatment groups. They say zinc cough drops, don't work. One well-designed study stated a positive effect on treating a common cold with zinc nasal gel. But the study results have not yet been duplicated.

2. Vitamin C. For many years, believers in vitamin C have said taking this vitamin supplement can stop a cold in its tracks. The belief is partially triggered by lab studies that find vitamin C affects resistance to virus in animal research.

But in human beings? Scientists disagree on this slightly but lean toward the negative. Some say vitamin C has not been proven to reduce the duration of an average cold. One 2007 scientific study showed that if vitamin C is taken after a cold starts, it doesn't shorten the cold or make it less severe. But when it is taken daily as a preventive treatment, not just after that first runny nose, it can very slightly decrease cold duration, by about 8% in adults and by about 14% in children.

Very athletic people, marathon runners, for instance, might cut their risk of a common cold in half by taking the vitamin, the study also showed.

But Dr. Gwaltney doesn't see it that way. The extensive evidence and the well-done studies prove that vitamin C does not keep us from getting colds, says Gwaltney. It might have some mild effect on treating colds.

3. Echinacea. The herbal supplement echinacea, like Vitamin C, sparks argument among cold experts. Advocates say it's an immune booster with antiviral characteristics and other benefits, so it's good at keeping away colds. However, two recent studies on the natural remedy have yielded conflicting conclusions. In one 2007 research, University of Connecticut scientists concluded that echinacea reduces the odds of developing a cold by 58% and reduces its duration by 1.4 days. But a previous study, conducted by Gwaltney's colleagues at the University of Virginia and published in 2005 in The New England Journal of Medicine, showed no benefit from the herb in either reducing the severity of a cold infection or preventing a cold.

Echinacea drew a "no" vote from our three experts -- Gwaltney, Blandino, and Owen Hendley, MD, professor of pediatrics in the division of infectious diseases at the University of Virginia, Charlottesvile.

4. Chicken Soup. Supporters of hot chicken soup, forever as a cold treatment, say it could possibly help soothe inflammation that can make the symptoms worse.

The problem with proving scientifically that chicken soup is effective, says Gwaltney, is finding a legitimate placebo food to research against it in a scientific manner. We were contacted by a soup producer to do research on chicken soup, he explains. We thought we could use another hot drink for placebo, he says. But it's got to be exactly like [like chicken soup]. They didn't find anything that was equal. Gwaltney calls chicken soup "a waste of time."

That's despite the well-publicized report published in 2000 in which researchers reported that chicken soup, which they studied in the laboratory, may have an anti-inflammatory effect on easing symptoms of upper respiratory infections. But the report doesn't prove chicken soup does anything for cold symptoms, Gwaltney says, because it didn't include a test of people nor include a placebo for comparison.

Even though chicken soup may not actually treat a cold, it can help treat dehydration that can occur when you have a cold or the the average flu.