Echinacea-Based Dietary Supplement Does Not Increase Maximal Aerobic Capacity in Endurance-Trained Men and Women

ABSTRACT

Purpose: To determine if an echinacea-based dietary supplement (EBS) provided at two different doses (a regular dose (RD), 8,000 mg/day, vs. a double dose (DD), 16,000 mg/day) would increase erythropoietin (EPO) and other blood markers involved in improving aerobic capacity and maximal oxygen consumption (VO₂max) in endurance-trained men. Secondly, to determine if any sex differences exist between male and female endurance-trained athletes. Methods: Forty-five endurance athletes completed three visits during a 35-day intervention. Participants were randomized into placebo (PLA; n = 8 men, n = 7 women), RD of EBS (n = 7 men, n = 8 women), or DD of EBS (n = 15 men) for the 35-day intervention period. At baseline, weight, body composition, and VO₂max were measured. Blood was drawn to measure EPO, ferritin, red blood cells, white blood cells, hemoglobin, and hematocrit. At the mid-intervention visit, blood was collected. At the post-intervention visit, all measurements from the baseline visit were obtained once again. Results: There was a significant increase in VO₂max for endurance-trained men in PLA (increase of 2.8 ± 1.5 ml kg⁻¹ min⁻¹, p = .01) and RD of EBS (increase of 2.6 ± 1.8 ml kg⁻¹ min⁻¹, p = .04), but not in DD of EBS (p = .96). Importantly, there was no difference in the change in VO₂max between PLA and RD of EBS. For endurance-trained women, VO₂max did not change in either treatment (PLA: −0.7 ± 1.7 ml kg⁻¹ min⁻¹, p = .31; RD of EBS: −0.2 ± 2.4 ml kg⁻¹ min⁻¹, p = .80). There were no significant changes in any blood parameter across visits for any treatment group. Conclusions: This EBS should not be recommended as a means to improve performance in endurance athletes.

KEYWORDS. :

• dietary supplement
• endurance athletes
• red blood cells
• sex differences
• VO₂max