Black cohosh is a woodland perennial herb native to eastern North America. It is frequently known as Cimicifuga racemosa (L.) Nutt.; however, molecular systematic studies have demonstrated that the genera Cimicifuga and Actaea should be combined, an old-fashioned taxonomic opinion that has now been revived. Black cohosh was traditionally used for menopausal and menstrual problems, to ease childbirth, and for conditions such as bronchitis, rheumatism, and nervous conditions; an alcoholic extract or tincture is the normal dosage form. Black cohosh has also become a popular ornamental due to its attractive large compound leaves and showy spikes of fluffy white flowers; it does not require full shade. Several Asian species have similar medicinal uses.

Several clinical trials of black cohosh products for menopausal symptoms have been conducted; these have not been absolutely conclusive, as results have varied and most trials have been small or used dated methodology. However, the weight of the evidence does suggest that high-quality cohosh products can reduce hot flashes. Presumed active ingredients include a suite of triterpene glycosides such as actein and cimicifugoside. The mechanism of action is not well understood, although it may involve influence on the temperature-regulating system of the brain. The plant was presumed to be estrogenic because it was once reported to contain the phytoestrogen formononetin, and perhaps because the only pharmaceutical drugs for menopausal symptoms were estrogenic. However, modern studies have found no formononetin in black cohosh, and in animal studies it has virtually no estrogenic activity (although one rodent study using other species of Cimicifuga found that extracts reduced osteoporosis after removal of the ovaries); whatever black cohosh?s primary mode of action is, it probably is not estrogenic. Side effects in human studies are mild, and cohosh is generally considered to be safe; a six-month rodent study using huge doses reportedly observed no toxicity. A few anecdotal reports have attempted to link black cohosh to cases of liver diseases in consumers, but causality in those cases is not proven and sometimes quite dubious. Previous studies make it clear that black cohosh is not hepatotoxic, but it might potentially be able, in a few susceptible people, to trigger idiosyncratic liver dysfunction, as has been reported for other substances. Because of the concern that black cohosh might stimulate a miscarriage, pregnant women should avoid this plant.

Selected References

Compton, J. A., A. Culham, and S. L. Jury. 1998. Reclassification of Actaea to include Cimicifuga and Souliea (Ranunculaceae): phylogeny inferred from morphology, nrDNA ITS, and cpDNA trnL-F sequence variation. Taxon 47:593-634.

Huntley, A. 2004. The safety of black cohosh (Actaea racemosa, Cimicifuga racemosa). Expert Opin. Drug Saf. 3:615-623.

Li, J. X., S. Kadota, H. Y. Li, T. Miyahara, Y.W. Wu, H. Seto, and T. Namba. 1996/97. Effects of Cimicifugae rhizoma on serum calcium and phosphate levels in low calcium dietary rats and on bone mineral density in ovariectomized rats. Phytomedicine 3:379-385.

Lloyd, J.U., and C. G. Lloyd. 1884-85. Drugs and Medicines of North America. Robert Clarke & Co.: Cincinnati, OH. [Reprinted in Bull. Lloyd Lib. 30, 1931.]

Low Dog, T. 2005. Menopause: a review of botanical dietary supplements. Am. J. Med. 118 (12 Suppl. 2):98-108.

Lupu, R., I. Mehmi, E. Atlas, M. S. Tsai, E. Pisha, H. A. Oketch-Rabah, P. Nuntanakorn, E. J. Kennelly, and F. Kronenberg. 2003. Black cohosh, a menopausal remedy, does not have estrogenic activity and does not promote breast cancer cell growth. Int. J. Oncol. 23:1407-1412.

Mahady, G. B. 2003. Is black cohosh estrogenic? Nutr. Rev. 61(5 Pt. 1):83-86.

Mahady, G. B. 2005. Black cohosh (Actaea/Cimicifuga racemosa): review of the clinical data for safety and efficacy in menopausal symptoms. Treat. Endocrinol. 5:177-184.

Ramsey, G. W. 1987. Morphological considerations in North American Cimicifuga. Castanea 52:129-141.

Ramsey. G. W. 1997. Cimicifuga. Pp. 177-181 in: Flora of North America Editorial Committee, eds. Flora of North America, vol. 3. Oxford University Press: New York.