Can Black Cohosh Decrease Blood Pressure & Hot Flashes?

Black cohosh was an important medicinal herb to Native Americans and 19th-century European settlers to treat fever and respiratory disorders. Today, the plant has a reputation as a remedy for hot flashes in menopausal women and, some say, to lower blood pressure. Although research appears promising, studies of its efficacy and safety are ongoing. Check with your doctor to determine whether black cohosh therapy is right for you.

Pharmacology

The "Physicians' Desk Reference for Herbal Medicines" lists several active constituents in black cohosh roots and rhizomes, including glycosides, isoferulic acid, cimifugoside and triterpene saponins collectively referred to as 26-deoxyactein. Some compounds in black cohosh may produce estrogen-like effects in the body.

Blood Pressure Effects

According to the American Cancer Society, black cohosh is historically used to decrease blood pressure. However, there is no evidence-based science to substantiate this claim. The "Physicians' Desk Reference for Herbal Medicines" says that studies conducted during the 1980s indicate that black cohosh preparations may increase the effects of anti-hypertensive medications and actually lead to high blood pressure.

Hot Flash Relief

According to the National Institutes of Health, or NIH, several studies have been done on black cohosh as a treatment for hot flashes, but the majority didn't use a placebo control or used a scale to measure effects on multiple symptoms in addition to hot flashes, such as depression and insomnia. Those the NIH considers to have the best study design include an early German study involving breast cancer survivors. After two months of observation, the researchers reported a decrease in the incidence and severity of hot flashes in both the treatment and control group. It should be noted, though, that both groups contained a nearly equal number of patients taking tamoxifen, an anti-estrogen medication for breast cancer.

The NIH points to another German study that is one of the few that has measured the incidence and intensity of hot flashes apart from other menopausal symptoms. This study involved 80 menopausal women given either a placebo, conjugated estrogens or the standardized German black cohosh preparation known as Remifemin. The estrogen and placebo group experienced a decrease in hot flashes on a scale from 5.2 to 3.2 and 5.1 to 3.1, respectively. Hot flashes in the black cohosh group, however, decreased from 4.9 to 0.7.

Dosage

An evidence-based monograph prepared by the Natural Standard Research Collaboration published online by the Mayo Clinic states that an effective dose of this herb has not yet been established. However, the British Herbal Compendium suggests 40 to 200 milligrams daily of the dried rhizome or 0.4 to 2 milliliters ethanol tincture.

Safety

The NIH says that studies on the long-term effects of black cohosh are lacking. However, caution is warranted if there is a history of breast cancer due to the herb's potential estrogenic effects. In addition, this herb should be avoided during pregnancy and by anyone with liver disease. Consult your health care practitioner before using black cohosh if any of these conditions apply or if you are taking other medications.