Echinacea Tests Show Little Effect
MICHELE NORRIS, host:
If cleaning out the medicine cabinet is on your to-do list this summer, some scientists have a suggestion: Toss out the echinacea. Researchers at the University of Virginia say the herbal remedy used to treat the common cold doesn't work. NPR's Allison Aubrey reports.
ALLISON AUBREY reporting:
There's no shortage of research on the herbal remedy echinacea. Extracts of the purple flower have been studied at least 200 times in the last 50 years. Some of the most rigorous studies show the herb is not effective in fighting the common cold. But Dr. Ronald Turner of the University of Virginia and a few of his colleagues wanted to know for certain.
Dr. RONALD TURNER (University of Virginia): We weren't convinced that the studies that were available were definitive.
AUBREY: So Turner and his colleagues designed their own study. They recruited 400 UVA students, put them up in a hotel in Charlottesville and placed drops of a nasty cold virus up their noses.
Dr. TURNER: So then each day they're in the hotel, they actually have specimens taken for cultures. They report symptom scores to us.
AUBREY: And the researchers measured how their colds progressed over five days. What the students didn't know was how they were being treated. A week before the hotel stay began, the volunteers all started taking a liquid syrup. Half of them were given a 900 milligram dose of echinacea root; the others were given a placebo made out of water and alcohol. Both groups continued to take the syrup during their hotel stays. But by breaking the students into two groups and blinding them as to which syrup they were taking, researchers could see if the echinacea had any effect.
Dr. TURNER: I think what we tried to do was to design the study in such a way that it gave every opportunity to detect an effect of the echinacea. And since we didn't find anything, I think that's a pretty solid answer.
AUBREY: Several other blinded, controlled studies done in recent years have led to the same conclusion, though the companies who manufacture and market echinacea say you can't toss out some of the smaller industry-funded studies.
Mr. MICHAEL McGUFFIN (President, American Herbal Products Association): There's not a body of evidence that is only one way. There are numerous studies that have been done to show echinacea to be effective in the right dose.
AUBREY: Michael McGuffin is president of the American Herbal Products Association. His major complaint with this new study is that the dose of echinacea used with the students was about a third of the dose recommended by herbalists.
Mr. McGUFFIN: It's like conducting a study on the effect of a third of an aspirin and wondering why you've still got a headache.
AUBREY: The authors of the paper stand by the dose. For starters, they say there's no evidence from prior studies that the dose of echinacea would have changed the outcome. And the dose they chose falls in line with the recommendation of a German regulatory agency that evaluates the usefulness of herbs.
There's another reason why other echinacea studies may have gotten positive results, and Turner's research can shed some light on that. No one in his study knew what they were taking, but the student volunteers were asked what they thought was in the syrup they were taking. Ronald Turner says their assumptions made a difference in how they perceived their symptoms.
Dr. TURNER: The volunteers who thought they were getting the echinacea had a statistically lower symptom score than the volunteers who thought they were getting a placebo.
AUBREY: So Turner says there was quite a strong placebo effect in the study.
Dr. TURNER: That's why it's so critically important that we blind these studies and document that they were well-blinded, because we know that there is a reporting bias associated with what you perceive you got.
AUBREY: Turner's study was published today in The New England Journal of Medicine. Allison Aubrey, NPR News, Washington. Transcript provided by NPR, Copyright NPR.