Black Cohosh for Menopause: What the Evidence Says About Hot Flashes and Safety

Introduction

Hot flashes are sudden episodes of intense warmth and are among the most common symptoms experienced during the menopausal transition. Approximately 85% of women experience hot flashes during the perimenopausal and early postmenopausal years, making them one of the leading reasons women seek medical care. In addition to causing daytime discomfort, hot flashes frequently disrupt sleep and reduce quality of life, creating a need for effective and well-tolerated treatment options.

Hormone replacement therapy (HRT) remains the most effective treatment for menopausal symptoms and also helps reduce the risk of osteoporosis. However, concerns about potential adverse effects have limited its use. Studies have linked HRT to an increased risk of breast cancer, while findings from the Women's Health Initiative demonstrated that prolonged use of combined estrogen and medroxyprogesterone acetate may increase the risk of serious cardiovascular events. Starting HRT closer to the onset of menopause appears to reduce cardiovascular risk. As a result, many women seek effective non-hormonal alternatives that relieve menopausal symptoms without affecting the uterus, breast tissue, or blood clotting.

Soy and red clover supplements containing isoflavones have been evaluated in numerous randomized, double-blind, placebo-controlled clinical trials. However, the commonly recommended daily dose of 50 mg of isoflavones has generally failed to provide meaningful relief from menopausal symptoms or demonstrate significant bone-protective effects. Although these standard doses do not appear to affect breast or endometrial tissue, women taking substantially higher doses have experienced unwanted estrogen-like effects.

Because of these limitations, interest in herbal therapies as alternatives to HRT has increased considerably. One of the best-studied herbal products is Klimadynon®, which contains an extract of black cohosh (Cimicifuga racemosa).

Black Cohosh (Cimicifuga racemosa)

Non-hormonal herbal therapy may provide an alternative approach to managing menopausal symptoms, and Cimicifuga racemosa is among the most extensively studied options. Numerous clinical studies have evaluated its effectiveness and safety in women experiencing menopausal symptoms.

Historically, Native American populations used black cohosh to relieve muscle and joint pain, neuralgia, rheumatoid arthritis, menstrual cramps, and various gynecological complaints. Although native to North America, the plant is now widely cultivated in Europe.

Cimicifuga racemosa Has No Estrogenic Activity

Nearly three decades ago, researchers suggested that Cimicifuga racemosa contained estrogen-like isoflavones. However, subsequent studies failed to confirm this hypothesis.

Unlike estrogenic compounds, black cohosh extracts do not bind to estrogen receptors. In vitro studies using the BNO 1055 extract demonstrated no affinity for either estrogen receptor subtype.

Because estrogens stimulate the growth of hormone-sensitive breast cancer cells, researchers also examined the effects of black cohosh on MCF-7 breast cancer cells. Both isopropanolic extracts and the BNO 1055 extract inhibited rather than stimulated the proliferation of these estrogen receptor-positive cells (Figure 1).

Breast tissue also produces the enzyme aromatase, which converts androgens into estrogens. Laboratory studies have shown that ethanolic extracts of Cimicifuga racemosa inhibit aromatase activity in MCF-7 cells, suggesting a potential anti-estrogenic effect within breast tissue.

Clinical findings support these laboratory observations. In a large 6-month clinical study involving early postmenopausal women receiving BNO 1055, no increase in mammographic breast density or endometrial thickness was observed. Similarly, another study involving 65 women found no evidence of increased breast tissue density or cellular proliferation following treatment with an isopropanolic black cohosh extract.

Effects of Cimicifuga racemosa on Menopausal Symptoms

Experimental studies have shown that animals develop hot flash-like symptoms after ovariectomy, reflecting estrogen deficiency similar to menopause. These episodes are associated with pulsatile secretion of luteinizing hormone (LH).

Loss of estrogen increases secretion of gonadotropin-releasing hormone (GnRH), which subsequently raises LH levels. During the menopausal transition, fluctuations in GnRH and LH are thought to contribute to vasomotor symptoms, including hot flashes. These hormonal changes are closely linked to alterations in several neurotransmitter systems, including serotonin, dopamine, norepinephrine, and gamma-aminobutyric acid (GABA).

Animal studies demonstrated that ovariectomized rats develop significantly higher body temperatures than healthy controls. Administration of BNO 1055 black cohosh extract significantly reduced body temperature compared with untreated animals (Figure 2). Researchers suggest that this effect may result from compounds within the extract that influence neurotransmitter pathways regulating GnRH secretion.

Additional laboratory studies have shown that constituents of Cimicifuga racemosa interact with dopamine, norepinephrine, serotonin, and GABA receptors, all of which play important roles in thermoregulation and the development of hot flashes.

Because medications that influence these neurotransmitter systems, such as gabapentin and the selective serotonin reuptake inhibitor fluoxetine, are known to reduce vasomotor symptoms, researchers compared fluoxetine with black cohosh extract in a 6-month clinical trial involving 120 women with menopausal symptoms.

Using the Kupperman Menopause Index, menopausal symptoms improved by 85% in women treated with Cimicifuga racemosa extract, compared with a 62% improvement among those receiving fluoxetine. As expected, fluoxetine remained more effective for treating depressive symptoms.

Researchers believe the beneficial effects of black cohosh arise from the combined action of multiple biologically active compounds rather than from a single active ingredient.

Summary

Cimicifuga racemosa has been used for centuries to relieve menopausal symptoms, and numerous studies support its effectiveness in reducing hot flashes and other vasomotor symptoms. Evidence suggests that low to moderate doses are more effective than higher doses.

Unlike hormone replacement therapy, black cohosh does not exhibit estrogenic activity and does not act through estrogen receptors. Instead, its effects appear to result from compounds that influence dopaminergic, noradrenergic, serotonergic, and GABAergic neurotransmitter pathways involved in thermoregulation.

Klimadynon® contains a standardized dry extract of Cimicifuga racemosa and is used to relieve menopausal symptoms such as hot flashes, facial flushing, and excessive sweating. As a non-hormonal herbal preparation, it offers an alternative option for women seeking relief from menopausal symptoms without using estrogen-containing therapies.

Prepared by: Dr. Jūratė Bazevičienė

Source: Internistas, No. 3, 2017.