Which herbal cold remedies really work?

By Carla K. Johnson
The Associated Press
CHICAGO (Feb 7, 2007)

It's cold and flu season, so many turn to herbal remedies that have been used for thousands of years.

But what is the scientific evidence for alternative cold and flu remedies, such as echinacea, ginseng and zinc?

The evidence is weak, says Dr. Ronald Turner, a cold virus expert at the University of Virginia School of Medicine.

Here is a quick look at the evidence:

* Echinacea: The herbal supplement is made from purple coneflower. Early studies suggested some benefit, but more recent studies with better designs have found no effect on preventing colds or lessening their length or severity. One study found that about half the echinacea products didn't contain the species listed on the label.

* Zinc: An essential mineral, zinc is found in oysters, beans, nuts and seeds. You can buy zinc in nasal sprays, lollipops, gum and lozenges. Studies have yielded mixed results. There are reports of damage to the sense of smell from zinc nasal sprays. High daily doses (80 mg) have been linked to urinary problems.

* Vitamin C: Found in fruits and vegetables, vitamin C has been found, in some studies, to reduce the duration and severity of colds when taken daily in doses of 200 mg or more. Other studies found nothing. Turner thinks there's "probably little true effect." Vitamin C can cause gastrointestinal problems in high doses.

* Ginseng: Traditional Chinese medicine uses the extract of this root to restore energy. The commercial herbal supplement Cold-fX contains ginseng. Some studies have found ginseng reduces the number and severity of colds. Turner says the studies were poorly designed. Another study found that most ginseng products contained less than half of what was listed on the label. Ginseng may cause insomnia.

* Oscillococcinum: Studies have not produced strong evidence of the effectiveness of this homeopathic medicine, which is made from minuscule amounts of duck hearts and livers.

* Chicken soup: Some studies suggest its vapours warm up the respiratory passages and loosen mucus. Chicken soup's ingredients are known antioxidants and it keeps patients hydrated. Known side-effects include feelings of comfort and nostalgia.