Dried Echinacea Offers No Cold Relief
Meal plan examples
Click Here
New Insights Emerge on Why Past
Studies Produced Mixed Findings
Echinacea may be a
hot seller as a cold remedy, but the scientific evidence that it works
has been inconclusively lukewarm -- at least in studies done in the U.S.
Some findings suggest that the popular supplement can shorten or
minimize symptoms, while others show no benefit. In the latest
study, published in the Dec. 17 issue of Annals of Internal Medicine,
University of Wisconsin researchers found no difference in the
length or severity of symptoms between 148 cold-infected college
students taking echinacea and those who received a placebo. The average
duration was six days in both groups. But the lead
researcher tells WebMD "there are some qualifications that may help
explain" his results -- and why other studies produce inconclusive
findings. And it's not just because all his study participants were
20-year-old college students, whose strong immune systems are less
likely to reap the full reported immune-boosting properties of the
controversial herb.
It's the echinacea
"mixture" that was used in the study. "The product we
used in our trial was a dried, unrefined leaf and root mixture," says
Bruce P. Barrett, MD, PhD, assistant professor of family medicine at the
University of Wisconsin-Madison Medical School. "Previous trials that
have shown a benefit have mostly used an extract and have been conducted
with one of two different species."
Besides using dry
leaves, which theoretically would have less of the suspected healing
substances, the mixture used in Barrett's study was a combination of two
species of echinacea, which is the world's best-selling herbal
supplement and second in the U.S. only to ginkgo biloba.
"We went this way
because we found a company that would produce this mixture and we
figured if we included both the root and the herb of those plants, we
would get in a little bit of everything," he tells WebMD. "This way, if
just one of those parts of the plants was active, at least we would have
some of it in there." Welcome to the
stew that has dished up a modern-day controversy over an ancient herbal
remedy used for centuries to treat a variety of conditions from coughs
and digestive problems to snakebites and gonorrhea. Despite conflicting
study findings, research suggests that echinacea increases immune
response, specifically in the number and mobility of infection-fighting
white blood cells that kill viruses that cause colds, flu, and other
upper respiratory infections. Whether proven or not, it is the world's
most popular cold remedy -- especially in Europe. But the problem in
proving its effectiveness in U.S. studies stems from this dilemma:
Echinacea is not a single plant, but a group of nine species. And three
- E. purpurea, E. angustifolia, and E. pallida -- are used
in varying amounts and dosages in over-the-counter products. Trying to
identify the active ingredients or how they work has eluded scientists,
and as a result, they have tinkered with different combinations of
species and plant parts. Hence, the mixed study findings. "With echinacea,
different preparations are used in different studies, which explains why
there is no conclusive evidence," says Mark Blumenthal, director of the
American Botanical Council (ABC), an independent, nonprofit organization
not affiliated with herbal manufacturers that publishes a peer-reviewed
journal of medicinal plants. "With ginkgo, milk thistle, St. John's wort,
and the better-documented phytomedicines, there are one or two leading
brands or extracts that are the basis for most of literature, and as a
result, produce more conclusive findings."
Blumenthal, who
teaches medicinal chemistry at the University of Texas College of
Pharmacy, says most studies showing that echinacea can shorten colds and
decrease symptom severity use the extracted "juice" from roots or fresh
leaves of either E. purpurea or E. pallida -- the two species
used in Barrett's study. "But there is no evidence to date that dried
leaves will offer any benefit," he tells WebMD. The council, which
tracks clinical trials of herbal medicines, reports that in 21 studies
on 3,500 people that compared these extracted mixtures to a placebo, 18
showed that echinacea can shorten the duration of a cold and ease its
symptoms. There is no compelling evidence that it prevents colds, as
some advocates maintain, says Blumenthal.
"One obstacle to
the performance of definitive studies in this issue is the fact that
different medicinal preparations of echinacea have different
compositions," says Ronald B. Turner, MD, of the University of Virginia
School of Medicine, in an editorial accompanying Barrett's study. He is
heading a $2 million study funded by the National Institutes of Health
hoping to identify what echinacea plant parts and manufacturing
processes deliver the most effective results.
"I certainly
wouldn't take the results of my study to mean not to take echinacea,"
says Barrett, who has personally reviewed 250 papers on the plant's
cold-fighting properties and headed a well-respected analysis on 13
published studies (showing mixed but optimistic results). "But I also
wouldn't take results of other studies that show benefit as advice to
take it. We don't know that it works. But we do know there is a very
strong placebo effect for the common cold. It could very well be
possible that people take echinacea or something else and think
they feel better. And as a result, they do."
WebMD Medical News Dec. 16, 2002 SOURCES: Annals of Internal Medicine,
Dec. 17, 2002 • Bruce P. Barrett, MD, PhD, assistant professor of family
medicine, University of Wisconsin-Madison Medical School • Mark
Blumenthal, director, American Botanical Council; adjunct associate
professor of Medicinal Chemistry, University of Texas College of
Pharmacy; and editor, HerbalGram.
Back to top
