Despite the consistently disappointing results, doctors aren't ready to discourage patients from taking echinacea quite yet.
"I think they need to figure out if echinacea thwarts the common cold from coming on, " he says.
The echinacea pills were provided by MediHerb, an Australian manufacturer of herbal products.
Their supposed uses range from echinacea to treat the common cold to saw palmetto for the symptoms of prostate enlargement.
Still, if you ask the scientists, wine has better grounds to call itself a health food than does, say, echinacea!
That added up to about 10 grams of echinacea on the first day and roughly 5 grams per day thereafter.
A., reported a study suggesting that echinacea was no better at preventing colds than a placebo (a pill with no active ingredients).
In the flower beds, coneflowers such as echinacea and rudbeckia turn into food as the blooms go to seed this time of year.
The effect of echinacea may vary according to the dose, how it's prepared, and even whether it's taken on an empty stomach, Dr. Firshein says.
The researchers didn't test whether echinacea alleviates colds already in progress.
And echinacea's ability to prevent (rather than improve) colds still isn't fully understood, says Jordan Josephson, MD, a sinus specialist at Lenox Hill Hospital, in New York City.
The echinacea sold in drugstores comes in a wide range of liquids, pills, powders, and tinctures, which can be derived from some combination of the plant's root, flower, or stem.
Dr. Rakel and his colleagues used pills made from the roots of two species of echinacea, Echinacea purpurea and Echinacea angustifolia, which are found in most commercially available echinacea products.
In a new study of more than 700 people who came down with colds, echinacea pills were not measurably better than placebo at speeding recovery time or reducing the severity of runny nose, sore throat, cough, and other symptoms.
Although echinacea proved ineffective, the people who took it experienced no side effects of note, which suggests that the remedy is generally safe, says Michael Perskin, MD, an assistant professor of medicine at NYU Langone Medical Center, in New York City.
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