"Our study didn't show any benefit of using echinacea to treat the common cold," said Steven H. Yale, M.D., a Marshfield Clinic internal medicine specialist and assistant director of Clinical Research, Marshfield Clinic Research Foundation.
The study involved 128 individuals who were enrolled and randomized to receive either 100 milligrams of echinacea as a freeze-dried, pressed juice from the aerial portion of the cone plant, or a lactose placebo. Participants, who had to be within the first 24 hours of the onset of cold symptoms, were randomly assigned to take one of the two preparations. They were not told which of the identical-appearing medications they received.
Participants were asked to take the preparation three times a day until cold symptoms were relieved or at the end of 14 days, whichever came first. They subjectively scored their symptoms, including sneezing, nasal discharge, nasal congestion, headache, sore or scratchy throat, hoarseness, muscle aches and cough in a daily diary.
"One limitation of our study is that our sample size was small," Yale said. Yale, who collaborated with Marshfield Clinic Biostatistician Kejian Liu, Ph.D., advocates more research on echinacea. "I would not recommend echinacea to treat the common cold until large, randomized studies are performed that confirm it is effective in lessening the symptoms or shortening their duration," he said.
Echinacea, touted in some studies as having the ability to shorten the duration of a cold or the severity of its symptoms, is one of a host of herbs that comprise a more than $5.1 billion industry in the United States. One fifth of adults take at least one herb regularly, with echinacea representing 10 percent of sales.
The reason studies may contradict each other about benefits for certain herbs can be found in differences in study design, according to Yale. There are three major species of cone flowers, from which echinacea is produced. Also, preparations vary depending on what part of the plant is used in the drug.
The Marshfield Clinic system consists of 41 patient care and research and education facilities in northern, central, eastern and western Wisconsin, making it one of the largest comprehensive medical systems in the United States.
Archives of Internal Medicine