You've washed your hands frequently and avoided crowded stores during post-holiday sales, and yet you've caught another cold. "What could I have done to prevent this?" you may ask. A new study reported in the Canadian Medical Association Journal may have found an answer in extracts of American ginseng (Panax quinquefolius) (2005, vol. 173, no. 9).

Researchers at the University of Western Ontario and the University of Alberta found that taking two capsules daily of a standardized ginseng supplement reduced the frequency of colds and the severity of cold symptoms. The study followed 279 people ages 18 to 65 who had at least two colds during the previous cold and flu season. Over the four-month test period, only 1 out of 10 participants taking a ginseng supplement suffered two or more colds, but nearly 1 out of 4 in the placebo group had more than two colds. And when those taking ginseng did get a cold, they experienced fewer days of symptoms.

The study offers hope for Americans who suffer from an estimated 1 billion colds every year. According to the study, ginseng extract may be effective against colds because of its ability to enhance lymphocyte function and initiate immune responses. However, researchers caution that further studies are needed to determine its usefulness in preventing upper respiratory tract infections in children and the elderly.