Stanford Report, March 9, 2005

Echinacea unproven to have value as cold treatment

First-year medical student finds fatal flaws in studies that claim to show the herb is beneficial in treating the common cold

BY JONATHAN RABINOVITZ

Thomas Caruso

The genesis of Thomas Caruso's paper in the latest issue of Clinical Infectious Diseases arose a few years ago when his father had a cold and was taking Echinacea to make it go away.

"It just got me wondering whether it really worked," said Caruso, who is now a first-year medical student. "I knew my dad and all of these other people were buying it, but was there any proof that it was effective as a cold treatment?"

That question led Caruso, then a junior majoring in biochemistry at the University of Virginia, to embark on a research project, under the direction of Jack M. Gwaltney Jr., MD, a professor of internal medicine, emeritus, at that university. They scoured the medical archives for studies and reviewed the findings.

Their conclusion?

"The possible value of Echinacea in treating the common cold has not been established," they write in the March 15 edition of the journal.

This is not the first review of the effectiveness of Echinacea, but it's noteworthy for the way it scrutinizes previous studies of this herb, which is now a fixture on the shelves of health food stores and supermarket chains.

Echinacea, a flowering plant found in the central and southwestern United States, was used centuries ago by American Indians to treat various ailments. According to the paper, use of Echinacea dropped at the start of the 20th century with the advent of antibiotics, but its popularity picked up in recent years, with sales of Echinacea teas, pills and droplets now estimated at more than $300 million annually.

What surprised Caruso was how few studies had been done of the herb—and how almost all of them had a fatal flaw. After doing extensive database searches, he and Gwaltney discovered only nine studies on its effectiveness as a cold treatment—six concluding that it had benefits, three finding that it didn't.

Caruso and Gwaltney then evaluated how well each of these studies met 11 criteria of experimental soundness they had selected and were struck that none of the positive studies met all their standards, though two of the three negative ones did so. The criteria they used to judge the validity of each study included whether they had a quantifiable hypothesis, validated case definition and, most significantly, proof of blinding.

None of the six positive studies met this last criterion. That alone, Caruso said, invalidates the results. Each of these studies hinges on participants receiving either a placebo or Echinacea and not knowing which they have received; such blinded studies are necessary so that participants' perceptions are not influenced in a particular direction.

"A lot of researchers say their studies are blinded, but it's not enough to just say so," Caruso remarked. "You have to prove that the participants don't know whether they're getting the placebo."

That's particularly relevant in studies involving Echinacea, as the herb has a distinct bitter taste—even in its tablet form—that participants could identify, he added. In addition to the problems with proof of blinding, a quantifiable hypothesis was lacking in four studies, as was validated case definitions, not to mention other discrepancies.

The lessons of the paper go beyond Echinacea. Gwaltney explained that the standards it poses would be useful in evaluating other studies. "The paper is significant because it reviews evidence on Echinacea treatment for colds but more so because it provides a well-reasoned framework for evaluating work on treatments that are not regulated by the FDA," Gwaltney said in an e-mail. "We are in a new golden age of medical fraud. It is time to reverse the process."

Caruso acknowledged that the results of his study are unlikely to change the minds of many people who now use Echinacea as soon as they start to sniffle. "A lot of people don't want to hear studies, they just say, 'It works for me,'" he said.

But at least one person has stopped using the herb since Caruso began work on the study. He noted that his father is no longer using Echinacea, though Caruso wasn't sure that his dad's decision had anything to do with his research.

And Caruso said his father continued to be an inspiration for his work. "This summer I may be doing part two of this research," he remarked, noting that his father still follows another popular remedy to treat his colds. "This time around," he added, "I want to look at zinc."