Is Echinacea a Proven Immune System Booster?
A large body of evidence from lab, animal, and human studies shows echinacea has numerous effects on the immune system. The three most prevalent and studied species of echinacea (E. purpurea, E. pallida, and E. angustifolia) stimulate both nonspecific (innate) and specific (adaptive) immune functions. All echinacea species appear to have a greater effect under conditions of mild stress on the immune system.(58)
Conflicting Study Results
Many of the studies may initially appear to present conflicting results. However, this is not necessarily an accurate indication of echinacea's effectiveness in boosting the immune system. In reality the parameters from one study to another are rarely the same, and conclusions from research on one particular component extracted from a specific species of echinacea are not necessarily conclusive evidence across all species.(8)
A good example of this is the highly publicized, well-designed study led by Dr. Robert Turner from the University of Virginia's School of Medicine on the efficacy of echinacea to prevent and treat cold symptoms. The negative study results deterred at least some further research on echinacea by the scientific community. However, Dr. Turner himself cautioned against drawing broad, generalized conclusions from the results of this study, which was conducted only on a species of echinacea that the German Commission E had not approved for medicinal use (E. angustifolia).(8)
Research has shown that some of the impediments to consistent results in the research of echinacea (and for all botanicals/herbs) for medicinal purposes include:
- Contamination by bacteria which may cause stimulation of an immune response not related to echinacea.(58)
- Extracts derived from the whole plant yield different (and often more potent) results than from isolated components.(12, 58)
- Season it was harvested in.(3)
- The bioactive constituents, and the effects they render, differ between parts of the plant used.(3)
- The method and materials used to extract the potentially bioactive components from the plants impact the effect.(58)
- Variations between species.(3, 8)
- Where the plant grew.(58)
Specific Immune System Effects by Species
The immune system effects of the three main species of echinacea found in recent studies include:
| Immune System Benefit | E. purpurea | E. pallida | E. angustifolia |
|---|---|---|---|
|
Stimulates phagocytosis |
Yes, some isolated constituents and whole echinacea extracts.(46) (lab, animal, & human clinical studies) |
Yes, some isolated constituents and whole echinacea extracts.(46) (lab, animal, & human clinical studies) |
Yes, some isolated constituents and whole echinacea extracts.(46) (lab studies) |
|
Anti-inflammatory |
Yes, some isolated constituents and whole echinacea extracts.(46) (lab, animal, & human clinical studies) |
Yes, some isolated constituents and whole echinacea extracts.(46) (lab & animal studies) |
Yes, some isolated constituents and whole echinacea extracts.(46) (lab studies) |
|
Yes, some isolated constituents and whole echinacea extracts.(46) (lab studies) |
Yes, some evidence of benefit in a clinical study with an E. pallida supplement.(73) |
Yes, isolated echinacoside constituents.(68) (lab studies) |
|
|
Yes, some isolated constituents and whole echinacea extracts.(46) (lab studies) |
Yes, echinacea root extracts.(68) (lab studies) |
Yes, echinacea root extracts.(68) (lab studies) |
|
|
Antiviral (including against HIV, cold, flu, and herpes simplex I viruses, but not against herpes simplex II virus)(46, 68) |
Yes, some isolated constituents and whole echinacea extracts.(46, 68) (lab, animal, & human clinical studies) |
Yes, some isolated constituents and whole echinacea extracts.(46, 68) (lab, animal, & human clinical studies) |
Yes, against many viruses but not against cold and flu viruses at dosages given in clinical trial.(8) However, E. angustifolia significantly improved effectiveness of flu vaccine in another clinical study.(74) (lab and clinical studies) |
|
Yes, some isolated echinacea constituents:(46)
(lab studies) |
Yes, echinacea root oil.(73) (animal studies) |
Yes, echinacea root oil.(73) (animal studies) |
Recommendations and Cautions for Use
The evidence is inconclusive as to echinacea's potential health benefits or risks for people with autoimmune disorders or systemic viral/bacterial immune diseases, such as:(22, 46, 58)
Anecdotally it has been used to treat some of these conditions (such as TB). Lab, animal, and clinical studies demonstrate that echinacea exhibits antiviral effects with HIV.(22, 46, 58)
Recent research evidence also suggests that autoimmune diseases are linked to defective natural killer (NK) immune cell functionality. In studies using blood samples from patients with chronic fatigue syndrome and AIDS, echinacea increased the effectiveness of NK cells in getting rid of infected cells.(22, 46, 58)
Other short term clinical trials have demonstrated echinacea's immune-enhancing benefits in patients with compromised immune systems. Echinacea seems to work best when taken with a 1-2 week break every couple of months. In clinical test subjects who were at higher risk of getting a cold or flu, E. purpurea appeared to have a preventive effect when taken daily.(11, 46)
However, echinacea has also been shown to stimulate production of certain inflammatory proteins. Some researchers suggest this may cause disease progression in patients with auto-immune disorders. Although not conclusive, there have been isolated reports associating lupus flare-ups with echinacea. In general, experts recommend restricting echinacea usage in patients with systemic immune disorders (whether autoimmune or bacterial/viral).(11, 22, 46)
Interestingly, results of one clinical trial suggest that E. purpurea does not appear to affect immune reactions in healthy people. This suggests that echinacea works more in an adaptive fashion instead of just blindly stimulating the immune system.(11)