Study: Echinacea Cuts Colds by Half
Skeptic Remains Unconvinced by New Analysis
WebMD News Archive
June 26, 2007 -- Taking the herbal supplement echinacea can cut your chances
of catching a cold by more than half and shorten the duration of a cold by an
average of 1.4 days, a new review of the research shows.
Researchers from the University of Connecticut combined findings from 14
previously reported trials examining echinacea to prevent or treat the common
While many of the most rigorous trials failed to show a significant benefit
for the supplement when reported alone, the combined trial analysis showed a
much stronger benefit, the researchers say.
Use of the herbal supplement was found to reduce the risk of catching a cold
by 58%, while the combination of echinacea and vitamin C reduced cold incidence
by 86% in one study.
But a longtime critic of the study of echinacea as a cold remedy remains
unconvinced by the new analysis.
Wallace Sampson, MD, who edits the Scientific Review of Alternative
Medicine, tells WebMD that the reviewed studies were too different to
provide meaningful results when pooled together.
“If you have studies that measure different things, there is no way to
correct for that,” the Stanford University emeritus clinical professor of
medicine says. “These researchers tried, but you just can’t do it.”
Echinacea and the Common Cold
Echinacea, a collection of nine related plant species found in North
America, is the most widely used herbal supplement in North America. More than
800 products contain some form of the herbal in the U.S., according to the
University of Connecticut researchers.
While more than 70 studies examining the use of echinacea for colds were
identified, C. Michael White, PharmD, tells WebMD that only the highest-quality
trials were included in the analysis.
In studies that involved volunteers being directly inoculated with a
cold-causing virus -- considered the most rigorous trial design -- use of
echinacea was found to reduce cold incidence by 35%.
White says the reduced effectiveness in these trials may mean that echinacea
is better for preventing natural virus exposure than exposure to the single
rhinovirus used in the trials.
More than 200 individual viruses are known to be capable of causing the
The analysis is published in the July issue of the journal Lancet
“When you combine the best studies they support the conclusion that
echinacea reduces the risk of catching a cold and reduces the duration of
colds,” White says. “What we don’t know is whether or not long-term exposure to
echinacea is safe.”