Getting to the root of black cohosh's uses
DOES IT WORK?Black cohosh is often used in place of HRT, but does it have much impact?
MENOPAUSE IS a natural part of ageing, and begins as production of female hormones (particularly oestrogen) decreases. When it occurs varies, but it signals the end of a woman's child-bearing years. For some, the transition is relatively smooth, but for others it is a difficult time emotionally or physically.
Hot flushes, depression, vaginal dryness and irritation are the most common symptoms. Hormone replacement therapy (HRT) became very popular until long-term studies published in 2002 found that some women were at risk of serious side effects.
Many women then turned to natural approaches to treat their menopausal symptoms, with black cohosh being one of the most popular.
Black cohosh is made from the underground parts of a North American plant that Native Americans called squawroot.
Evidence from studies
Recent interest in black cohosh began in the 1980s when several clinical studies were conducted with a German product called Remifemin. This product is of a type called a standardised extract.
Herbs naturally produce varying amounts of different ingredients, some of which can have medicinal properties. The amounts of these active ingredients vary with growing and production conditions.
When the active ingredients are known, manufacturers can ensure each batch contains a specific quantity. This is called a standardised product.
Remifemin is standardised to contain specific amounts of triterpene glycosides (although whether these are the active ingredients is unclear). All the German studies in the 1980s found that women improved with the herb and reported no adverse effects.
However, seven of these studies were not double-blinded. In other words, the women knew what they were receiving. Many studies have found that this tends to lead to more positive results than when studies are double-blinded.
Since those early studies, a small number of double-blind studies have been carried out and the results have varied widely. Most of these were conducted for three months or less. Only one found black cohosh of more benefit than placebo.
The largest and longest randomised, double-blind trial to date was published in 2006. Women were randomly put into groups taking black cohosh, a multiherb product, a placebo, soy products, or HRT. Only the group taking HRT had significantly better results compared to placebo. This study lasted one year, and during that time the menopausal symptoms in the placebo group decreased by almost one-third in both frequency and severity.
Thus, many women can expect their symptoms to improve over a year without taking anything.
Most women have no side effects from black cohosh, although intestinal problems and rashes can develop. These are usually rare, mild and reversible. On very rare occasions, liver problems have been reported.
Herbalists have traditionally used black cohosh to induce labour, leading many to urge that it not be used during early pregnancy or breast-feeding.
Blue cohosh and white cohosh are completely unrelated plants and should not be used in place of black cohosh.
Black cohosh appears to bring relief from some menopausal symptoms and is generally safe to take. However, much of the herb's reputation is based on traditional use and older trials that were not designed as well as possible.
More recent, better-designed studies have not had similarly positive results. Most producers recommend taking two to four milligrams of triterpenes daily.
Products vary in how much active ingredient they contain per tablet. Given the herb's good safety profile, it may provide some benefit for those who do not want to use hormonal therapies.
Dónal O'Mathúna has a PhD in pharmacy, researching herbal remedies, an MA in bioethics, and is a senior lecturer in the School of Nursing, Dublin City University. He is author of Alternative Medicine: The Christian Handbook (Zondervan, 2007)