Genetic analyses found herbs similar to black cohosh were being sold in commercial preparations of the popular remedy, possibly explaining mixed results and casting doubt on supplement label accuracy
A pure pill? Some black cohosh pills sequenced did not contain black cohosh at all, but rather entirely different plant species.
Image: iStockphoto/OlgaMiltsova
When hormone replacement therapy was found to put some menopausal women at increased risk of cancer and cardiovascular disease, many went in search of safer treatments to decrease their symptoms. In the ensuing decade black cohosh has won out as an overwhelming consumer favorite, now reaping millions of dollars in sales each year.
But controlled trials of this supplement have seen mixed results, sometimes showing it to be effective in relieving hot flashes, sleep disruptions, mood swings and other symptoms whereas other times revealing it to be ineffective. And some case reports even suggest that it can be toxic, damaging the liver.
This messy track record gave Damon Little, a bioinformaticist at The New York Botanical Garden (NYBG), and his colleagues an idea: What if patients?in these trials and out in the community?were not always taking pure, actual black cohosh (Actaea racemosa), but one or more related species? Fortunately, they had just the tool on hand to figure that out: DNA barcoding.
Using this technology, which locates and sequences specific areas of a plant's genome (specifically, two matK gene nucleotides), they were able to determine that one quarter of commercially available "black cohosh" pills were not the herb at all. Their findings were published this July in the Journal of AOAC International.
"Misidentification and adulteration in black cohosh supplements [has been] known for many years as a matter of concern," notes Rolf Teschke, an internist at the Teaching Hospital of the Johann Wolfgang Goethe University in Frankfurt and who was not involved in the new research. "The present study confirms?but extends?previous findings."
Unlike drugs, however, supplements are not required to be tested for safety or efficacy by the U.S. Food and Drug Administration before they hit the market. And testing to make sure the contents match the label are much more lax than it is for pharmaceuticals, opening the opportunity for mislabeling, whether it is accidental or intentional.
Wild roots
Black cohosh has been used traditionally by Native Americans as a natural remedy for a variety of ailments. It is often harvested in the wild, where it grows in similar environments to many of its close cousins that look very similar. And some species of Actaea are suspected to be toxic to humans. "Unless you're looking very carefully, you can't assume that any black cohoshlike thing is actually black cohosh," Little says. In eastern North America, where black cohosh grows, it is not uncommon to also find yellow cohosh (A. pachypoda and A. podocarpa) and baneberry (A. spicata and A. rubra). During harvesting, the rhizomes (buried stems) are often collected and then ground up to make the supplements, leaving telling botanical clues, such as leaf shape, forever lost.
In recent years, with the vast increase in the herb's sales, commercial growing operations have also sprung up in North America as well as Europe and Asia.
David Baker, a gynecologist at Stony Brook University Medical Center, had many patients who took black cohosh, but he was intrigued by the ambiguity of the medical literature on the supplement. So he, Little and their colleague at the NYBG, Dennis Stevenson, wanted to see if all of these pills labeled as black cohosh were, indeed the correct species.
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