Echinacea (Echinacea purpurea) is an herbal supplement derived from a North American perennial plant (Purple Coneflower) that is primarily used as a non-specific immunostimulant. Anecdotal evidence suggests that supplementation with Echinacea can shorten the duration and/or severity of the common cold. However, the prospective mechanisms related to the possible immune-enhancing affects of Echinacea remain to be identified.
PURPOSE: To determine whether four weeks of oral Echinacea supplementation altered resting leukocyte responses.
METHODS: Twenty-four apparently healthy and recreationally active males age 24.9 ± 4.2 yrs, height 178.9 ± 7.9 cm, weight 87.9 ± 14.6 kg and 19.3 ± 6.5 % body fat were randomly assigned to either an Echinacea (ECH; n=12) or a placebo (PLA) group. Subjects were required to be free of any symptoms of upper respiratory tract infections (URTI) for seven days prior to starting the study. Participants were supplemented with 8 g-day1 of ECH or PLA (wheat flour) for 28 consecutive days. Fasting, morning blood samples were collected prior to and at weekly intervals for four weeks and were analyzed for white blood cell counts (WBC), lymphocytes, neutrophils, monocytes, eosinophils and neutrophil/lymphocyte (N/L) ratio. Subjects were queried during each visit regarding illness symptoms or other changes in health status. Frequency, severity, and duration of events were recorded. ANCO VA was used to determine if significant differences existed between or within the groups during the four weeks of supplementation with initial differences between groups serving as a covariate. Significance was set at ? = 0.05.
RESULTS: There were no significant differences (P > 0.05) between ECH and PLA for WBC, neutrophils, monocytes or eosinophils at any time. However, the N/L ratio was significantly lower between ECH (1.79 ± 0.14) and PLA (2.37 ± 0.36, p <0.05) at wk 4. ECH induced an 18.9% increase in neutrophils from wk 2 (2.85 ± 0.17 × 10−1mL1) to wk4(3.39±0.28 × 10−1mL−1, p <0.01), an 11.4% decrease in monocytes at wk 2 (0.44 ± 0.03 × 10−1mL−1) vs. baseline (0.49 ± 0.05 × 10−1·mL−1, p <0.05) and wk 1 (0.49 ± 0.06 × 10−1·mL−1, p <0.05), and a 28.0% and a 21.7% decrease in eosinophils at wk 3 (0.18 ± 0.04 × 10−1mL−1 fromwk 1 (0.25 ± .07 × × 106·mL−1 p <0.01) and wk 2 (0.23 ± 0.06 × 106·mL−1, p <0.05), respectively. No subjects in either ECH or PLA reported any symptoms of URTI or other changes in health status during their four week study period.
CONCLUSIONS: These data suggest that oral supplementation of 8 grams-day−1 of Echinacea purpurea for 28 days did not induce clinically relevant alterations in leukocytes at rest.