America's on-again, off-again romance with echinacea could be on again.
The popular herbal supplement, made from the purple coneflower, might reduce the chances of catching a cold by 58 percent, according to the latest in a long line of confusing and contradictory studies.
Better yet, echinacea might reduce the length of a cold by an average of 1.4 days -- a substantial savings, because colds cause 40 percent of the nation's lost work time, the authors of a recent study say.
The study, conducted by scientists from the University of Connecticut, is published online today in The Lancet Infectious Diseases, a British medical journal. Echinacea is a herb with a long-standing medicinal reputation among Americans, who spend an estimated $2 billion a year on nonprescription cough and cold remedies.
Over the years, studies of echinacea have shown "a trend of improving colds," but none involved enough patients to be statistically significant, said the author of today's article, Dr. Craig Coleman of the University of Connecticut's School of Pharmacy.
Other studies have shown just the opposite. In 2000, German scientists reported that echinacea could help treat colds but not necessarily prevent them. In 2005, a study of more than 400 patients published in the New England Journal of Medicine indicated that echinacea had no effect on colds at all.
Coleman's team performed a meta-analysis, combining the results of 14 independent studies involving more than 1,600 patients.
Some experts say that's still not good enough. They argue that Coleman's meta-analysis combines too many studies with different combinations of drugs.
"Some of the patients were also taking Vitamin C, rosemary, thyme ... you really don't know what's going on," said Dr. Adriane Fugh-Berman, associate professor of complementary and alternative medicine at Georgetown University.
To compensate for this problem, Coleman said, his team did a "sensitivity analysis" to determine whether echinacea worked on its own.
"There was still reduction in cold duration," Coleman said, but not enough to be statistically significant.
Archaeologists say American Indians used echinacea more than 400 years ago to toughen their immune systems and treat wounds. Herbalists prescribe it today for urinary and yeast infections, ear infections and hay fever.
Although echinacea is generally regarded as safe, the American Herbal Products Association cautions those with pollen allergies to avoid it. The same goes for asthmatic patients, particularly children, according to Fugh-Berman, who said it often makes their condition worse.
"I've had [asthma] cases where the child will get better as soon as you stop giving them echinacea," she said.
Doctors also advise patients with autoimmune diseases, diabetes, multiple sclerosis and HIV infections to avoid the herb, according to the Web site of the Baltimore Washington Medical Center.
Coleman has conducted safety research, to be published later this summer. In that study, researchers gave echinacea to healthy patients while they monitored their blood pressure and electrocardiogram readings. Both were normal.
"In a short-term basis, this drug is relatively safe," Coleman concluded.
Although he said his analysis was thorough and proved the herb's effectiveness on colds, Coleman conceded that there's still a lot to learn.
"There are nine species of echinacea, and there are three that are known to have medicinal qualities," Coleman said. "Each of those species have different dosage forms in different portions."
Coleman's work might result in more federal funding for echinacea studies, according to Dr. Brian Berman, director of the Center for Integrative Medicine at the University of Maryland.
What's harder to get, Berman said, is drug company funding, which is critical to conducting clinical trials that would test echinacea more conclusively.
"A pharmaceutical company wouldn't be able to exclusively market the medication because it is not patentable," Berman said.
Still, he said the latest analysis might trigger a wave of public interest in the drug, as studies in the early 1990s did for St.-John's-wort as a treatment for depression.