Americans spend millions of dollars annually on the herbal remedy echinacea, but a government-sponsored study shows they might be throwing their money away.

Researchers at the University of Virginia School of Medicine tested almost 400 volunteers to see whether echinacea helps prevent infection from a cold virus or reduces the severity of cold symptoms.

"It's not clinically effective," Ronald Turner, an expert on the common cold at the University of Virginia School of Medicine and lead author of the study, was quoted by USA Today as saying. "It had no effect on the rate at which volunteers got infected or on their symptoms."

People buying echinacea to ward off runny noses, sore throats, headaches and other symptoms of the common cold are wasting their money, Turner said.

Americans spend about $150 million a year on the herbal remedy to treat their colds, according to the Nutrition Business Journal.

The study, published in the New England Journal of Medicine, is the "most sophisticated" test ever done on the effectiveness of echinacea, said Stephen Straus, director of the National Center for Complementary and Alternative Medicine, which financed the work.

Researchers gave the volunteers echinacea extract or a placebo for seven days before putting drops containing rhinovirus up their noses. The volunteers then stayed alone in hotel rooms for five days so that they could not be infected by anyone else.

Those taking echinacea in three different forms had about the same symptoms as those taking the placebo treatments.

Echinacea enthusiasts took exception to the study's conclusions. They noted that only the root portion of one version of the plant from which echinacea is derived was used and said the dosage given was too low.

"This is a good contribution to the clinical literature, but it is not the definitive study on echinacea," Mark Blumenthal, executive director of the American Botanical Council, was quoted by London's Telegraph as saying. "I just wish it had been a bigger study with bigger dosages."

One of the study's co-authors, Dr. Rudolph Bauer, a professor of pharmaceutical biology at the Karl-Franzens University in Graz, Austria, also said further study was warranted with other echinacea species and with other preparations and with different doses.

Dr. Jen Tan, medical director of Bioforce U.K., a herbal remedy manufacturer, told the Telegraph not all echinacea products are equivalent, because there are variations in quality, species of echinacea and extraction method.

"For our products, which have been shown to be clinically effective against colds and flu, we use the plant species echinacea purpurea, and we extract with an alcohol-water solution," Tan said. "This study uses a different species, with less alkamides -- the important active ingredient -- and a different extraction method."

Source: Deutsche Presse-Agentur