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BY OUR PHARMA CORRESPONDENT
July 30, 2005: The herbal extract of echinacea does not have any preventive properties against cold, suggests a study published in a leading medical journal.
The herbal supplement made from purple coneflower is being used by millions world over to prevent or treat colds. The reports of a large and rigorous study published in The New England Journal of Medicine says that echinacea neither prevented colds nor eased cold symptoms. Some had hypothesized that interleukin-8 was stimulated by echinacea, enabling the herb to stop colds.
The study, involved 437 people who volunteered to have cold viruses dripped into their noses. Some swallowed echinacea for a week beforehand, others a placebo. Still others took echinacea or a placebo at the time they were infected.
The subjects 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.
But the investigators found that those who took echinacea fared no differently from those who took a placebo: they were just as likely to catch 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.
However, some researchers believe that we still need further investigation, with stronger doses and with echinacea species and preparations different from those used in this study.
But many researchers strongly hold the view that echinacea is not an effective cold remedy. While the herb is generally safe, some people are allergic to it, and it can lower blood levels of theophylline, a drug used by people who have asthma, as well as levels of medications used to treat diabetes.
The study originated at the national center, which has been exploring the efficacy of supplements Americans were consuming.
A national survey last year by the National Center for Health Statistics found that echinacea was the most popular natural product, used by some 14,665,000 people, or 40 per cent of those who used natural products. The American Botanical Council, a nonprofit group that promotes the use of herbal supplements, says sales of echinacea products in 2004 were about $155 million.
A few years ago, the National Center for Complementary and Alternative Medicine sponsored two other large studies of echinacea, one in children and the other in college students. In both studies, patients who already had a cold took the herb, which had no effect on their symptoms or the cold's duration when compared with a placebo.
The centre took the opportunity to study echinacea as a cold preventative with the most rigorous and sensitive test available. To begin with, the 300-milligram dose was determined by a world-renowned expert, Dr. Rudolph Bauer, a professor of pharmaceutical biology at the Karl-Franzens University in Graz, Austria. That dose was one that had been employed in previous studies and the one that the World Health Organization had described as most often used by consumers.
And the investigators were looking at the relevant measures of infection and symptoms in their search for the virus and interleukin-8.
The American Botanical Council also called for more research. Mark Blumenthal, the group's founder and executive director, said in a press release that among other things, the herb should be tested at a higher dose.
But in an editorial accompanying paper said there was no reason to have believed that echinacea was effective against colds in the first place. In the early 20th century, echinacea "somehow became popular for the treatment of respiratory illness in Germany," while in the United States it was used for wound healing and other purposes for which today people would take an antibiotic. Its use faded away when real antibiotics were discovered, but it re-emerged in the 1960's as a cold remedy, with no particular reason to think it would work.
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