Black cohosh (Cimicifuga racemosa) for menopausal symptoms: A systematic review of its efficacy

Abstract

Since conventional hormone replacement therapy has fallen out of favour, alternatives are being sought by many women. These therapies include herbal preparations such as black cohosh (Cimicifuga racemosa). The purpose of this update of a previous systematic review is to evaluate the clinical evidence for or against the efficacy of black cohosh in alleviating menopausal symptoms. Five computerized databases (Medline, Embase, Amed, Phytobase and Cochrane Library) were searched to identify all clinical data that provided evidence on the efficacy of C. racemosa. Bibliographies of the articles thus located were scanned for further relevant publications. Only double blind, randomized, clinical trials (RCTs) were included in the evaluation of efficacy. No language restrictions were imposed. Trials were excluded if they did not focus on menopausal problems, they included women suffering medically induced menopause, they did not use black cohosh monopreparations, or they did not use placebo or a standard drug treatment for the control group. Six studies with a total of 1112 peri- and post-menopausal women met our inclusion criteria. The evidence from these RCTs does not consistently demonstrate an effect of black cohosh on menopausal symptoms; a beneficial effect of black cohosh on peri-menopausal women cannot be excluded. The efficacy of black cohosh as a treatment for menopausal symptoms is uncertain and further rigorous trials seem warranted.

Introduction

Menopause usually occurs at the age between 45 and 54 years when the ovarian function begins to decrease [1]. About 25 million women pass through menopause worldwide each year, and it has been estimated that, by the year 2030, the world population of menopausal and postmenopausal women will be 1.2 billion, with 47 million new entrants each year [2].

Menopausal estrogen deficiency is associated with vasomotor, vaginal and psychological symptoms including hot flashes, vaginal dryness and bone loss in up to 85% of women [3]. Hormone replacement therapy (HRT) is an effective intervention for these complaints [1]. However, findings of two recent large randomized clinical trials (RCTs) [4], [5], implied that the risk associated with HRT may outweigh the benefits for women on continuous estrogen and progestin regimens. Many patients and clinicians are therefore hesitant to continue using HRT [6], [7]. Various alternative therapies for managing menopausal symptoms are on offer, particularly herbal preparations [8], [9], [10]. These herbal preparations are regulated either as dietary supplements or as approved herbal drugs depending on national requirements.

Back cohosh (Cimicifuga racemosa or Actaea racemosa) is amongst the most thoroughly studied herbal medicine for the treatment of menopausal symptoms [11], [12]. It is a perennial herb native to North America, a member of the buttercup family (Ranunculaceae). Extracts of the rhizome of C. racemosa have been traditionally used for a variety of female complaints including pain during childbirth, uterine colic and dysmenorrhea [13] C. racemosa rhizome contains triterpene glycosides [actein, 23-epi-26-deoxyactein (formerly called 27-deoxyactein), cimicifugoside], phenolic acids (isoferulic acid and fukinolic acid), flavonoids, volatile oils, tannins and other pharmacologically active ingredients [13], [14]. Contrary to some publications, black cohosh does not contain formononetin neither kaempferol nor genistein and is not to be classified as a phytoestrogen [11]. The pharmacological effects of black cohosh may best be described as selective estrogen receptor modulation (SERM) augmented by central nervous effects [11]. The activities are believed to be the result of complex synergistic actions of several components. Preparations made from the rhizome of C. racemosa are widely marked as herbal remedies for the treatment of menopausal symptoms, and US sales figures were $9.7 million in 2005 [15].

The aim of this systematic review, which is an update of our previous review [16], is to summarize and critically evaluate the clinical evidence for or against the efficacy of C. racemosa in providing relief of menopausal symptoms.