But a recent study has cast doubts on the effectiveness of black cohosh in relieving the symptoms.

Looking back, native Americans were known to have used black cohosh to treat rheumatism, malaise, malaria, colds, constipation and hives. According to the National Institutes of Health's website, this was also prescribed for lung and neurological conditions as well as labor pain, infertility and threatened miscarriage during the 19th century.

The number one brand of black cohosh supplement is Remifemin, manufactured by a German company, Schaper & Bruemmer.

Last year, Australia and some European countries required all supplements labels to indicate a warning about liver toxicity. This was due to reports of many hepatitis cases in black cohosh users.

The authorities in those countries believe that the contributing factor to the problem is the fact that treatments of menopause symptoms has not undergone intensive studies. This includes black cohosh. They said that only estrogen was widely studied and its uses and risks were clearly identified.

Another complicating issue is the regulation of black cohosh under foods, not drugs, by the Food and Drug Administration, which is why there are many black cohosh brands in the market, it being a dietary supplement.

The contents of a dietary supplement, unlike drugs, can always be modified without changing labels. According to physician Adriane Fugh-Berman, professor in the complementary and alternative medicine master's program at Georgetown University's School of Medicine, "Remifemin" sold in table form today, is used to be a liquid.

Last month's issue of Annals of Internal Medicine published the results of a year-long study of 351 women administered with a daily dose of 160 milligrams of black cohosh. According to the publication, the trial showed that black cohosh "was no more effective than a sugar pill."

Dr. Tieraona Low Dog, director of education for the Program in Integrative Medicine at the University of Arizona Health Sciences, doubts whether the scientists who made the latest study gave the right dosage.

"The dose for black cohosh may be much higher than that used in this trial," Low Dog says. "Imagine if we did a trial on ibuprofen administering 40 milligrams every six hours for arthritis pain. If it didn't work any better than placebo, one would conclude it was ineffective. However, the truth would be that the dose was inadequate."

Another question on the study was the use of a different type of alcohol on the black cohosh than what is used in Remifemin. Fredi Kronenberg, a Columbia University scientist and director of the Richard and Hinda Rosenthal Center for Complementary and Alternative Medicine, notes that "no one knows whether that might boost or inhibit its effectiveness."

Makers of Remifemin, Schaper & Bruemmer, in defense, reiterates that it is a "safe and effective intervention for the relief of hot flashes and other vasomotor symptoms associated with menopause."

Many women have sworn the effectiveness of Remifemin and other black cohosh supplements. But Low Dog observed that "those who think that herbal medicine is ineffective, the study provides further confirmation." But, for those who believe in it, the study is an example of how researchers were incorrect, she added.