Is Black Cohosh a Phytoestrogen?
Is Black Cohosh a Phytoestrogen?
By Donald Brown, ND, Founder and Director, Natural Product Research Consultants, Inc.; Advisory Board, American Botanical Council; President's Advisory Board, Bastyr University, Seattle; Advisor to the Office of Dietary Supplements at the National Institutes of Health. Dr. Brown is a consultant for Nature's Way, Inc.
Source: Wuttke W, et al. Effects of black cohosh (Cimicifuga racemosa) on bone turnover, vaginal mucosa, and various blood parameters in postmenopausal women: A double-blind, placebo-controlled, and conjugated estrogens-controlled study. Menopause 2006;13:185-196.
Abstract: In a randomized, multicenter, double-blind, placebo-controlled clinical trial, the effects of a standardized black cohosh extract were studied in 62 perimenopausal women (ages 40-60 years), who were experiencing at least three hot flashes per day. Subjects were randomized to receive either 20 mg black cohosh (Cimicifuga racemosa [L.] Nutt., Ranunculaceae [syn. Actaea racemosa]) rhizome, 0.3 mg of conjugated estrogens (CE), or placebo bid for three months. The black cohosh (BC) extract used in the trial (BNO 1055, Klimadynon®/Menofem®) was supplied by Bionoriaca AG, Neumarkt, and is a dried aqueous/ethanolic (58%, v/v) of the rhizome (standardization specifics are not provided).
The primary outcome measures and results were presented in an earlier paper.1 Clinical analyses for this paper focused on the secondary outcome measures of the clinical trial. Blood samples were collected at baseline and at weeks 4, 8, and 12 and used to measure luteinizing hormone (LH), follicle-stimulating hormone (FSH), sex hormone-binding globulin (SHBG), estradiol (E2), progesterone, as well as lipid parameters including total cholesterol (TC), HDL-cholesterol, LDL-cholesterol, and triglycerides (TG). Additionally, the levels of CrossLaps (the C-terminal breakdown product of bone specific collagen-1α1—a marker of bone degradation) and bone-specific alkaline phosphatase were measured by immunoassays and enzymatic assay, respectively. At baseline and at week 12, all subjects had complete gynecological examinations including transvaginal ultrasound for determination of endometrial thickness and vaginal smear to determine the maturity index of vaginal epithelium. Routine safety laboratory parameters were analyzed at baseline and week 12. These included SGOT, SGPT, and GGT.
Immunoreactive levels of E2 were significantly higher after weeks 4, 8, and 12 in the CE group compared to placebo (P < 0.05). This effect was not noted for the BC group. CE suppressed serum FSH significantly, whereas no significant effect was noted for LH. BC had no significant effect on either measure. A slight decrease in SHBG was observed in the placebo and BC groups while the CE group had a significant increase (P < 0.05). CrossLaps was significantly decreased compared to placebo at week 12 in the CE group (P = 0.0181). Although there was a slight decrease in the BC group, it did not reach statistical significance compared to placebo. Bone-specific alkaline phosphatase remained unchanged in the placebo group and CE groups, but was increased significantly in the BC group at week 12 (P = 0.0358). This suggests an increased activity of osteoblasts, which are responsible for bone formation. Endometrial thickness was significantly increased by CE (P factor not given) and remained unchanged in the BC and placebo groups. There was a significant increase in the number of vaginal superficial cells in the CE group compared to the BC group (P = 0.01) and the placebo group (P < 0.0001). There was a moderate increase in the BC group which approached significance compared to placebo (P = 0.0542). There was a slight decrease in the number of superficial cells in the placebo group. There were no significant effects noted for CE or BC on TC, HDL-C, or LDL-C. Serum TG was significantly higher in both the CE and BC groups at week 4 (P < 0.05) and week 12 for BC (P < 0.05) compared to placebo. Liver enzymes were not increased by either BC or CE and at week 12, with a tendency toward decreased levels in the BC group.
Comments
Questions continue as to whether BC is a phytoestrogen with mild estrogenic actions or is devoid of any estrogenic activity. While earlier studies from Germany and the United States failed to find an effect of BC on serum estradiol, LH, or FSH levels and no effect on endometrial thickness, they did not look at markers of bone resorption nor superficial cells in the vagina. The results of this trial suggest that BC does have a mild effect on increasing vaginal superficial cells. Also noteworthy was the increased levels of serum alkaline phosphatase—an indicator of increased osteoblast activity.
In the discussion portion of the paper, the investigators report on in vitro tests that have found that the BNO 1055 extract has binding activity to cytosolic estrogen binding (receptor) sites of human, rat, or porcine origin, but not to recombinant human receptor α or β proteins (ERα or ERβ).2 The mode of action for BC preparations remains somewhat enigmatic, but may involve organ-specific ER enhancer or repressor genes. It also should be noted that there was no effect on LH levels in this study. The investigators suggest that one possible explanation for the efficacy of BC for the treatment of hot flashes is based on a serotoninergic effect.3
Practice Implications. Focusing on secondary findings of a 12-week clinical trial on the therapeutic effects of BC in perimenopausal women, this clinical trial suggests that the BC extract BNO 1055 (Klimadynon®) has a very weak effect on the vaginal mucosa compared to conjugated estrogen. A very interesting finding is the fact that BC seemed to increase osteoblast activity and therefore potentially influence bone formation. This should become a primary focus of longer-term studies on BC. Also of note in this trial, is the absence of hepatotoxicity—an issue that has cast a shadow over BC extracts in the past few years.4
References
1. Wuttke W, et al. The Cimicifuga preparation BNO 1055 vs. conjugated estrogens in a double-blind placebo-controlled study: Effects on menopause symptoms and bone markers. Maturitas 2003;44(Suppl 1):S67-S77.
2. Jarry H, et al. In vitro effects of the Cimicifuga racemosa extract BNO 1055. Maturitas 2003;44(Suppl 1):S31-S38.
3. Burdette JE, et al. Black cohosh acts as a mixed competitive ligand and partial agonist of the serotonin receptor. J Agric Food Chem 2003;51:5661-5670.
4. Blumenthal M. Australian TGA publishes liver warning policy for black cohosh. HerbalGram 2006;71:60-161.
Brown D. Is black cohosh a phytoestrogen? Altern Ther Women's Health 2006;9(10):78-79.Subscribe Now for Access
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