However, the results should be treated with caution because, even if it does change the floral balance in the gut, it is not known whether this would have a detrimental effect on health. Moreover, an industry representative told NutraIngredients.com that none of the 30 or so clinical trials with the herb have reported adverse effects like irritable bowel syndrome (IBS).
The study, said to be first to examine the effects of a botanical supplement on bacteria in the gastrointestinal (GI) tract, reports that Echinacea purpurea, one of the commonly used varieties of the herb, stimulated the growth of some Bacteroides bacteria, which may act as pathogens if the natural intestinal balance is upset.
Writing in the current issue of the Journal of Clinical Pharmacy and Therapeutics, authors Laura Hill, Jerald Foote and their co-workers said the study highlights the need for additional research, specifically larger studies, to target the specific bacteria affected and to determine if particular components or the combination of components in the herb were behind the apparent effects.
"Echinacea supplementation has altered the GI microbiota," wrote the researchers. "The health consequences associated with this change are unknown."
"Previous research has shown increased Bacteroides concentrations associated with diarrhoea, inflammatory bowel disease and increased risk of colon cancer," they said.
However, Daniel Fabricant, vice president, scientific affairs for the trade association Natural Products Association (NPA) cautioned that the recommended use of Echinacea purpurea is generally for short periods of less than eight weeks in order to support the immune system against colds, respiratory and urinary tract infections, "so it is not surprising it may have an effect on other bacteria (ie microflora)," he said.
"However, I'm not sure what the authors hope to accomplish by associating Echinacea use with some sort of health risk or unwanted consequence due to an increase in GI microbiota, when no adverse events like IBS have been observed either in clinical trials (over 30 with E. purpurea administered orally, 12 double blind) or the millions who have used E. purpurea safely and effectively," Dr. Fabricant told NutraIngredients.com.
"Without a control group the application of the data is limited. As a researcher it is irresponsible to draw any conclusion, let alone speculate about risks, especially where colon cancer is concerned," he said.
The new research from the University of Arkansas recruited 15 healthy adults and assigned them to a daily supplement of standardized E. purpurea (1000 mg, Natural Factors R&D, Canada) for 10 days. Samples of faeces were collected at baseline, 10 days and 17-18 days after supplementation, and selected aerobic and anaerobic bacteria populations were measured.
The researchers, who state they had expected null results, report that gastrointestinal bacterial counts were found to have increased for three groups of organisms during supplementation - the total group of aerobic bacteria, and for the anaerobic Bacteroides in general and Bacteroides fragilis in particular.
Hill and coworkers state that anaerobic bacteria - those that grow where there is no oxygen - make up most of the bacteria in the human colon. While Bacteroides are an important feature in the normal life of the colon, under certain conditions they also can act as pathogens, especially strains of B. fragilis, with some studies reporting that a specific strain has been linked to inflammatory bowel disease and diarrhea.
The supplements did not significantly affect enteric bacteria populations, like enterococci, lactobacilli, bifidobacteria or total anaerobic bacteria, said the researchers.
"Additional research should delineate the role of Echinacea in the stimulation of Bacteroides and describe the effects of other botanical supplements to the GI microbiota," they said.
This is not the first time that questions have been raised about the herb. A much-publicised study in the New England Journal of Medicine in July 2005 concluded that the herb did not have a significant effect on infection with a rhinovirus, but the methodology has been strongly questioned by herbal experts. In particular, the study did not use a commercially available product, and dosage was lower than the standard dose in the US - 1g per day compared to 3g.
Data from Euromonitor International indicates that such studies have taken a toll on sales. The market researcher saw a peak in UK retail sales of echinacea in 2003 at €6.1m, falling to €4.9m in 2005. Its projections are at odds with the retailers', expecting a compound annual growth rare of -2.8 per cent through to 2010.
Euromonitor's view on Western Europe as a whole is more positive, with 2005 sales at €163.7, in 2005 (down from €166 in 2004) and projected CAGR of 0.9 per cent through to 2010. But even though this is positive growth, it is still up against projected CAGR of 4.4 per cent for the entire dietary supplements category.
Source: Journal of Clinical Pharmacy and Therapeutics December 2006, Volume 31, Issue 6, Page 599 "Echinacea purpurea supplementation stimulates select groups of human gastrointestinal tract microbiota" Authors: L.L. Hill, J.C. Foote, B.D. Erickson, C.E. Cerniglia and G. S. Denny