Echinacea, the herbal remedy widely believed to prevent or ease the misery of the common cold, turns out to be no more effective than a placebo, according to a new study by the University of Virginia School of Medicine.

The finding, published in the New England Journal of Medicine, is the latest to show no benefit from the herb, which is widely billed as an immune system booster and promoted by advocates of "natural" remedies as a proven treatment.

Whether the conclusions will influence sales of echinacea is a matter of debate.

In a commentary in the Journal, Wallace Sampson, editor of the scientific Review of Alternative Medicine, said a study disproving the effectiveness of such remedies "rarely leads the supplement industry to reduce production or the public to decrease use. In fact, advocates often dismiss disproof."

The reputation of echinacea, also known as purple coneflower, is so vaulted that the herb is recommended by the World Health Organization as a treatment for the common cold.

The study, led by Ronald Turner of the University of Virginia, tested echinacea on 399 volunteers to determine whether any of three preparations had an active ingredient that reduced the risk of infection or symptoms if an infection took hold.

Although the researchers tested the echinacea species originally used by Native Americans in the Midwest and endorsed by WHO, the treatment was no more effective than a placebo.

There are many types of echinacea preparations, so it would be difficult to test them all, Turner said. "Our study, however, adds to the accumulating evidence that suggests that the burden of proof should lie with those who advocate this treatment."

In his commentary, Sampson said most of the previous tests that helped build echinacea's reputation "were of small, inadequately controlled studies sponsored by industry."

Turner's study was funded by the National Center for Complementary and Alternative Medicine, a government agency that pays for research largely on the basis of the popularity of the unconventional treatment.

"Since 1999, the ( National Institutes of Health) has spent almost $1.5 billion in grants for research into alternative methods. NCCAM has spent almost half that amount and has found no evidence of efficacy and little evidence of inefficacy," Simpson said.

He said it's time to devote that money to tests of treatments that have "passed through the sieve of plausibility and that is consistent with basic sciences, other applied sciences, and history _ all molded by wisdom and common sense."