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.
