Echinacea Powerless Against Common Cold?

MADISON, Wis.--Unrefined echinacea does not confer benefits above and beyond placebo for addressing symptoms of the common cold, according to research printed in the Nov. 17 issue of the Annals of Internal Medicine (137, 12:939-46, 2002) (www.annals.org). Researchers from the University of Wisconsin, Madison, conducted their randomized, double blind, placebo-controlled trial with 148 college students who were experiencing the onset of the common cold.

Students in the treatment group were given an encapsulated mixture of unrefined Echinacea purpurea herb (25%) and root (25%), and Echinacea angustifolia root (50%) taken in 1-gram doses six times on the first day of illness and three times on each subsequent day of illness for a maximum of 10 days. Efficacy was measured through self-reports of symptoms related to upper respiratory tract infection.

Researchers noted there was no significant difference detected between the treatment and placebo groups for any outcomes. Cold duration and severity was nearly identical in both groups, according to researchers, with the mean duration being about six days in both groups.

"In the study itself, the authors mention their results go against currently published evidence, and they discussed the limitations of their own trial," said Stephen Dentali, Ph.D., vice president of scientific and technical affairs for the American Herbal Products Association. "They basically come to the same conclusion that we do: Future research will be necessary, this goes against the currently published evidence, and previous trials have reported benefits."

Dentali added that the placebo used in this trial was alfalfa, which may not have been a completely inactive placebo. And, because the mechanism of action for echinacea has not been completely elucidated, this trial may have been doomed from the start, according to Dentali. "We know that echinacea affects immune cells in vitro," he said. "But we do not know--at least I haven't seen good evidence of what it does when you give it to healthy people--what happens to the immune system when someone takes echinacea. ... [I]f it's working, it's working by some mechanism, and understanding the mechanism of how echinacea is working might have told us that this trial would fail before it started. We don't know."