Yale SH, Liu K. Arch Intern Med. 2004;164:1237–1241
Pupose of the study.
Echinacea purpurea stimulates the immune response and is promoted to reduce symptom severity and the duration of upper respiratory tract infections. The researchers sought to determine the efficacy of a standardized preparation of Epurpurea in reducing symptom severity and duration of the common cold.
Study Population and Methods.
A randomized, double-blind, placebo-controlled design was used. Patients received either 100 mg of E purpurea (freeze-dried pressed juice from the aerial portion of the plant) or a lactose placebo 3 times daily until cold symptoms were relieved or until the end of 14 days, whichever came first. Symptoms (sneezing, nasal discharge, nasal congestion, headache, sore or scratchy throat, hoarseness, muscle aches, and cough) were scored subjectively by the patient and recorded daily in a diary. Kaplan-Meier curves were used to estimate the survival function of time to resolution in each group. The Wilcoxon rank-sum test was used to compare time to resolution between the 2 groups.
One hundred twenty-eight patients were enrolled within 24 hours of cold-symptom onset. Group demographic distribution was comparable for gender, age, time from symptom onset to enrollment in the study, average number of colds per year, and smoking history. No statistically significant difference was observed between treatment groups for either total symptom scores (P = .29–.90) or mean individual symptom scores (P = .09–.93). The time to resolution of symptoms was not statistically different (P = .73).
The preparation of E purpurea at these doses was not effective in relieving the severity or duration of the common cold.
It is probably not a surprise that inconsistent results have been found in different studies, because there is no required standardization for potency or content of echinacea. We can thank the US Congress, who in the mid-1990s capitulated to the food-supplements industry and removed Food and Drug Administration regulation of echinacea and other similar products. Although we generally think of echinacea as fairly harmless, it can reduce the effectiveness of corticosteroids, which would be commonly used in viral-induced asthma. It also can cause hypersensitivity reactions to persons allergic to ragweed.