Echinacea, the herbal remedy used by millions of Americans for fighting the common cold, does not ward off runny noses, sore throats or headaches, nor does it help speed recovery from cold symptoms, according to the results of a major clinical study released today.

"We find no evidence that it actually does anything to common cold symptoms," said Dr. Ronald Turner, a professor of pediatrics at the University of Virginia School of Medicine and lead author of the study reported in the New England Journal of Medicine. "If that's the reason you're buying it, then you're wasting your money."

While other studies have shown similar results, echinacea enthusiasts said they did not think the latest study merited such a clear-cut conclusion. They noted that Turner and his colleagues used only the root portion of one version of the plant from which echinacea is derived -- the purple coneflower -- and said the dosage given was too low to register any positive effect.

"This is a good contribution to the clinical literature, but it's not the definitive study on echinacea," said Mark Blumenthal, executive director of the American Botanical Council, a nonprofit group backed by herbal supplement makers whose logo includes a purple echinacea flower. "I just wish it had been a bigger study with bigger dosages."

Americans spent $153 million on echinacea products last year, making it one of the five best-selling herbs in the country, according to the Nutrition Business Journal, an industry publication based in San Diego. It comes in capsules, tablets, tonics, powders, lozenges, tea bags and even gummy vitamins for children. But spending has been declining steadily since 2001 as some users become disillusioned with the product, said editor Grant Ferrier.

"With a lot of herbal botanicals, including echinacea, there's not a tangible effect," Ferrier said. "It's not like taking a pill for a headache. A lot of it goes on faith."

The study included 437 people who volunteered to have cold viruses dripped into their noses. Some took echinacea for a week beforehand, while others got a placebo. Others swallowed echinacea or a placebo at the time they were infected.

Then the subjects, mostly college students, were secluded in hotel rooms for five days while scientists examined them for symptoms and took nasal washings to look for the virus and for an immune system protein, interleukin-8, which some had hypothesized was stimulated by echinacea, enabling the herb to stop colds.

But the investigators found that those who took echinacea fared no differently from those who took a placebo -- they were just as likely to get a cold, their symptoms were just as severe, they had just as much virus in their nasal secretions, and they made no more interleukin-8.

While some echinacea researchers say more study is needed, Dr. Stephen Straus, director of the National Center for Complementary and Alternative Medicine, which sponsored the new study, says he, for one, is satisfied that echinacea is not an effective cold remedy.

"This paper says it will not pre-empt a common cold, and it stands on top of prior studies saying it doesn't treat an established cold," Straus said. "We've got to stop attributing any efficacy to echinacea," he added.

Echinacea, a member of the same plant family as sunflowers and daisies, was used for hundreds of years by more than a dozen American Indian tribes to treat snakebites, toothaches, coughs and other ailments.

Western doctors began recommending it in the 19th century. It became popular in the United States in the 1960s as consumers embraced herbal alternatives to traditional medicine. No less an authority than the World Health Organization recognized echinacea as a treatment for colds in 1999.

In an accompanying editorial to the study, Dr. Wallace Sampson, an emeritus clinical professor of medicine at Stanford University School of Medicine, questioned why the government was wasting tax dollars on funding alternative medicine studies, some of which have turned out to be nothing but snake oil.

"Research into implausible remedies rarely produces useful information," wrote Sampson, who was not connected to the study.

But one of the study's co-authors, Dr. Rudolph Bauer, a professor of pharmaceutical biology at the Karl-Franzens University in Graz, Austria, said the study should be repeated with other echinacea species and with other preparations and with different doses.

"I am always in favor of further studies," Bauer said. He himself takes echinacea and will continue to take it, he says.