Athletics and Herbal Supplements
Do current products enhance athletes’ health and performance?
Echinacea is purported to boost defense against upper respiratory infections, so athletes use it primarily to offset the deleterious effects of intense training on immunity. Although the general public uses the genus name as the common name, genus Echinacea is comprised of nine species (some divided into subspecies). The three species most often used commercially are Echinacea angustifolia, E. pallida and E. purpurea.
Bioactive molecules produced by these species include alkamides, organic molecules made of fatty acids often found in plants, and phenols, another class of organic molecules also dubbed carbolic acids that are known for their acidity. Phenols encompass caffeic acid derivatives, echinacoside and ketones; distributions and quantities of these molecules vary by species. It is important to differentiate these molecules because the body processes them differently and they have different effects. Alkamides move from gut to bloodstream apparently unmodified within an hour. Complex carbohydrates have largely been discounted by multiple studies due to their inability to move from gut to bloodstream without modification. Roots contain the highest levels of these compounds, but oftentimes manufacturers will instead harvest aboveground parts, such as leaves and stems, to allow the plants to regrow and thus provide multiple harvests per planting. In North America, echinacea is most widely consumed as capsules or tablets.
Only five studies have been published concerning in vivo dosing of athletes with echinacea supplements (Figure 6). Studies by Aloys Berg of Albert Ludwigs University and collaborators and Heather Hall of Elmhurst College and collaborators reported reduced incidence or duration of upper respiratory infection events after intense exercise (such as competitive sprint triathlons or laboratory sprint cycling) in athletes dosed with E. purpurea supplements for four weeks either before or after a scheduled bout of exercise. The reduced incidence of infections was corroborated by molecular immunological data from blood, saliva and urine samples, demonstrating increases in circulating concentrations of certain antibodies and changes in circulating concentrations of several signaling molecules important in regulating inflammation (see Figure 6). White blood cells are the cells associated with the immune system, but no changes in white blood cell subsets or counts were identified. Taken together, the findings suggest that echinacea may reduce incidence and severity of upper respiratory infections by changing the quantities of immune molecules produced by white blood cells, rather than changing other aspects of white blood cells, such as their rate of multiplication or specific functions. In further support of the link between echinacea, exercise and upper respiratory infections, Roland Schoop and colleagues at Bioforce AG in Switzerland reported reduced incidence and duration of self-reported upper-respiratory-infection symptoms in athletes dosed in a similar manner to those in the previous two studies, when compared to a control group generalized from control data in previous studies.
Looking at physiological parameters important in athletic performance, Malcolm Whitehead, now at Stephen F. Austin State University in Texas, published two reports with colleagues from Troy University, College of Charleston and the University of Southern Mississippi on a recreational group of athletes, dosed with E. purpurea for four weeks and compared to placebo-treated controls. They found that common measures of aerobic performance—maximal oxygen consumption (VO2max), running economy (oxygen use efficiency) and erythropoietin (a hormone that controls red blood cell genesis)—were higher among the echinacea-treated group than among controls. However, the authors reported no differences in total red blood cell count, hemoglobin (the molecule within red blood cells that carries oxygen) or hematocrit (packed red blood cell volume) between the two groups. The fact that there were no changes in red blood cell–associated parameters but there were changes in performance parameters is difficult to interpret but may suggest that echinacea supplementation influences performance by modulating oxygen dynamics or metabolism at body sites distinct from the red blood cells themselves. Other scientific teams report relatively good tolerability and low side effects from echinacea supplements, although interactions with certain prescription medications have been documented.
In contrast to studies in athletes, studies of echinacea supplementation in the general population have yielded conflicting findings, likely due to the confounding factors discussed previously. Our team has endeavored to reduce the problem of preclinical factor variation by translating the concepts from our seed-to-stomach model into an experimental design adapted for athletic applications (Figure 7). We opted for an ex vivo approach, where white blood cells were taken from study participants before and after an acute exercise bout and then treated with echinacea extracts in the laboratory. This method, although less representative of the organismal context, allows us to more tightly control some variables.
We initially worked with white blood cells from resting donors to establish the effects of key preclinical factors. Several interesting findings accrued; for example, our lab and others have repeatedly demonstrated that different echinacea species vary in the way they modulate the immune system, probably because of differences in plant chemistry. We showed how deliberate choices in species, plant organ, solvent and extraction method influenced cell growth rates and production rates of immune system signaling molecules.
After the work in resting subjects we incorporated an acute exercise component, still controlling for the preclinical factors as we had in our previous studies. Early work conducted on teams of wrestlers and soccer players showed that the different species of echinacea plant, given in tincture form to the players’ white blood cells cultured under laboratory conditions, resulted in different effects on signaling molecules important during infection (Figure 8). We also showed that acute exercise changed how echinacea supplements interacted with the white blood cells. However, we have since switched to testing athletes individually on treadmills and stationary bicycles so we can better ensure that the amount of exercise is more consistent across subjects.
Collectively, data from studies of echinacea in athletes suggest that different species of echinacea have different effects on the human body, that exercise changes these effects and that effects are cell- and body site–specific. The work also suggests that preclinical factors have not been adequately accounted for across studies; further, preclinical factors are expected to vary greatly between manufacturers and even between batches from the same manufacturer. Given that awareness, and the understanding that so few studies have been conducted and often with small sample sizes, one cannot conclusively argue for or against the use of echinacea by athletes.