"Part of the problem surrounding the study of echinacea is that all of the products containing it are different," said principal investigator Dr. Ronald B. Turner, professor in the Division of Infectious Diseases, Department of Pediatrics, at U.Va. "No one has identified an active factor yet."
Numerous variables could influence what in echinacea works and how, Turner said. The part of the plant used, the growing conditions and season, how it is processed and which of the plant's three species -- each of which has a different chemical composition -- are in a product could all possibly affect its medicinal value.
The study will use one crop of echinacea plants processed using three different extraction methods to produce three different concentrations of various echinacea constitutents. The composition of these three products has been carefully characterized in the laboratory of a leading plant chemist at the University of Graz in Austria, a subcontractor for the study. These three products -- which are identical except for their extraction methods -- will be administered to study subjects.
"If you buy Product X off the shelf today and you go back six months later and buy the same brand, it may be completely different from the first thing you bought," Turner said. "Echinacea and other supplements present a huge problem with safety and standardization, as well as for research, because if you don't know what's actually in the product, studies on it can't be standardized, and therefore cannot get consistent results."
Turner and his research team plan to recruit approximately 450 subjects for the study. One group of subjects was enrolled in May, and the next group will be enrolled in October. The volunteers are infected with a cold virus. One group is given echinacea before being infected with the cold, and another group receives it after being infected. Some subjects in each group receive a look-alike placebo, or inactive medication, instead of the echinacea so they can be compared with the group receiving the herbal supplement.
"One of the things we want to find out is whether echinacea has an effect on viral replication or on the body's inflammatory response," Turner said. "It may involve a combination of several factors."
Echinacea is indigenous to the American Midwest, and was first used for medicinal purposes by Native Americans, according to ethnobotanists. White settlers adopted it as a folk remedy, and in the twentieth century, it became popular in Europe. Use of echinacea has revived during the past decade's herbal supplement production and sales boom in the United States.