No Evidence That Echinacea Treats Colds
Thu Mar 3, 2005 04:19 PM ET

By Alison McCook
NEW YORK (Reuters Health) - Most of the major studies on the effectiveness of echinacea for treatment of the common cold contain major flaws, suggesting that research has not yet established that this herbal medicine is effective, according to a new report.

Of nine studies evaluated, only two were well designed, and both showed that echinacea was not effective, study author Dr. Jack M. Gwaltney, Jr., told Reuters Health.

For Gwaltney, this suggests that researchers should consider spending their research dollars investigating other treatments that hold more promise. "If you ask me if I would study some more, I would say no," he said.

Americans currently spend more than $300 million per year on echinacea.

During the investigation, Gwaltney, based at the University of Virginia School of Medicine in Charlottesville, and his co-author Thomas J. Caruso of the Stanford University School of Medicine, evaluated nine clinical trials that compared echinacea with a placebo, considered the best way to figure out if a treatment works. Their findings appear in the journal Clinical Infectious Diseases.

Gwaltney explained that seven of the nine studies contained a fatal flaw. They did not show that people could not tell the difference between the placebo and the treatment. This is crucial, he explained, because research shows that there may be a placebo effect, meaning that if people think they are receiving treatment, they will get better faster, even if they are only getting placebo.

If the placebo looks, tastes or smells different from echinacea, the patients might figure out which treatment they are getting, which could markedly skew the results, Gwaltney noted.

In addition, four out of the nine studies did not measure whether people had taken the drugs as directed, the researcher added. This is also very important, he explained, since people need to take echinacea as directed to find out if it works.

Ways to measure compliance include counting pills, asking people to keep a log of what they take, and testing their urine, Gwaltney said.

Four of the nine studies also did not explain how they made sure the study participants had colds, as opposed to other similar conditions, such as hay fever, he added.

Gwaltney explained that of the nine studies they looked at, only two did not contain serious flaws. And the results of those two studies suggested that echinacea doesn't treat colds, he said.

Gwaltney added that nothing is ever 100-percent certain in science, and more well-conducted studies are needed before people can be confident that echinacea doesn't work.

In an accompanying editorial, Dr. Vernon Knight, of the Baylor College of Medicine in Houston, notes that these findings suggest that people who buy echinacea are simply wasting their money. Echinacea appears to be a "major unjustifiable cost of health care at a time when legitimate health care costs are escalating," he writes.

SOURCE: Clinical Infectious Diseases, March 15, 2005.