While the participants reported only minor side effects from taking echinacea, the researchers found that the amount of bacteria in the stool samples increased while the patients were taking the supplements. This suggests that the amount of bacteria in the gastrointestinal tract increased while the patients took these supplements.
While bacteria are supposed to be found in the gut, some types of bacteria can be potentially dangerous. In fact, one particular type of bacteria, Bacteroides fragilis, a known pathogen, was found in increased numbers in the participants’ stool samples. The results of the study were published in the Journal of Clinical Pharmacy and Therapeutics.
Study author, Jerald Foote, notes that the bacteria B. fragilis has been found in high concentrations in patients at high risk for colon cancer and one strain of this bacteria may contribute to inflammatory bowel disease and diarrhea.
More work needs to be done to firmly link echinacea use to dangerous gut bacteria, but as a result of his findings, Foote suggests that people limit their use of echinacea.