Does it or doesn’t it?
No one seems to know for sure, even the researchers who have studied whether the popular dietary supplement echinacea helps shorten the duration or intensity of that universal malady, the common cold.
A recent federally funded study involving nearly 150 healthy undergraduates at the University of Wisconsin found that the herb is no better than a placebo in treating a cold.
Researchers randomly assigned participants to take either echinacea or a placebo for 10 days and complete a questionnaire detailing the duration and severity of their symptoms. Those who took echinacea had colds that lasted an average of 6.27 days, while the placebo group’s symptoms lasted an average of 5.75 days–a difference of no statistical significance.
Yet even the study’s lead author, Bruce P. Barrett, an assistant professor in the department of family medicine, does not think his study should be the definitive judgment on the efficacy of echinacea, one of the best-selling supplements in the U.S., with an estimated $193 million in annual sales in 1999.
“I don’t think that this should be taken as the final word,” Barrett said. The chief reason for his caution, Barrett said, is the fact that his study contradicts a dozen other published reports concluding that echinacea does have some benefit in treating colds.
But these previous studies, Barrett said, have “significant limitations.” Some were funded entirely by manufacturers, while others did not appear to be sufficiently “blinded.” (Participants may have known whether they were taking echinacea or a placebo.)
Barrett noted that his team used pills containing the whole herb, not the liquid extract of echinacea, a form used in many previous studies. The pill form makes it more difficult to distinguish the placebo from echinacea, but may have affected the results because some researchers believe that the extract is more potent and effective than the whole herb form.
Side effects and warnings
Precautions: Echinacea could interfere with drugs used to suppress the immune system, such as those used by people who have had organ transplants. Also, people with HIV and lupus should not take echinacea because it could aggravate their conditions. Allergic reactions to echinacea are possible, especially among people with ragweed allergies.
