Modern day use of the herb is most commonly for menopausal symptoms but also pre menstrual syndrome (PMS) and irregular periods.
As women reach menopause, the signals between the ovaries and pituitary gland begin to diminish, which in turn reduces the production of estrogen, and increases the secretion of luteinizing hormone (LH). Hot flashes and other acute symptoms of menopause are thought to be related to these changes.
Early studies done on rats suggested a hormone-like effect of black cohosh. One of these study found that constituents in black cohosh did connect to the estrogen receptors in the uterus.
Another study found that the herb caused a decrease in the concentration of LH in the blood. The conclusion at that time was that black cohosh had a mild estrogen effect and also reduced the amount of LH, both believed to contribute to reducing hot flashes in menopausal women.
In recent years, however, both animal and human studies indicate that these early findings of the estrogen effect of black cohosh are not necessarily accurate. In a study done on mice and rats, it was found that black cohosh does not have any estrogenic properties.
The theory of the estrogen effect of black cohosh was further weakened when one of the best studies to date looked at the effect of the commercial black cohosh extract Remifemin® on menopausal women between 43 and 60 years. The women were administered either 40 or 127 mg of the extract daily for three months.
Although the frequency and severity of the hot flashes improved markedly and was similar at both dosages, there was no estrogen-like effect noted at all.
The conclusion was, therefore, despite earlier findings that black cohosh does not contain any phytoestrogens, and that women experience menopause symptoms should not look to it as an estrogen replacement.
In addition, isoflavones, a group of substances that include all phytoestrogens, rarely occur in plants other than those belonging to the pea family (Fabaceae ) such as soy (Glycine max) and red clover (Trifolium pratense). Black cohosh belongs to the buttercup family (Ranunculaceae).
Black cohosh is still, despite having probably no hormonal effects, regarded as one of the best natural options for a relief for hot flashes during menopause and it does not cause serious side effects and potential health risks (eg. increased risk of cancer) as estrogen substitutes have been known for.