1. Zinc. The mineral zinc, available in over-the-counter lozenges, nasal sprays, and gels, are said to work by not allowing the formation of proteins used a common cold virus to reproduce.

Despite all the hoopla about zinc for a remedy of a normal 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, have no effect. One well-designed study said there was a positive effect on treating an everyday cold with zinc nasal gel. But the study results have not yet been replicated.

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

But in humans? Researchers disagree on this slightly but lean toward the negative. Some say vitamin C has not been proven to reduce the time of a normal cold. One 2007 scientific study showed that if vitamin C is taken after a cold begins, it doesn't lessen the cold or make it less severe. But when it is taken daily as a preventive treatment, not just after that first sneeze, it can very slightly reduce 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 an average 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 prevent colds, says Gwaltney. It could possibly have some mild effect on treating colds.

3. Echinacea. The herbal supplement echinacea, similar Vitamin C, spikes argument among cold experts. Advocates say it's an immune builder 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 scientific study, University of Connecticut researchers came to the conclusion that echinacea reduces the odds of developing an average 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 common 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. Advocates of hot chicken soup, forever as a cold remedy, say it may help soothe inflammation that can make the symptoms worse.

The situation with proving scientifically that chicken soup is actually a treatment, says Gwaltney, is discovering a legitimate placebo food to research against it in a scientific way. We were contacted by a soup corporation to do a study on chicken soup, he explains. We thought we could use another hot beverage for placebo, he says. But it's got to look, smell, and taste [like chicken soup]. They didn't find anything that measured up. 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 actively treat a cold, it can help treat dehydration that can be present when you have a common cold or the the flu.