In a Canadian study, more than 300 adults who had at least two colds in the previous year took an American ginseng supplement or a placebo for four months. The result? People in the ginseng group got a lot fewer colds than those in the placebo group. And when they did get a cold, the symptoms were much less severe.
The ginseng supplement, known as Cold-Fx, can be found in most pharmacies. The standard daily dose for cold prevention is 200 milligrams; for active colds, it's 300 milligrams. "The research on this product is so significant that in Canada, it is allowed to be sold with a specific health claim for cold and flu prevention," says Ontario pharmacist Sherry Torkos, author of "The Canadian Encyclopedia of Natural Medicine."