Black cohosh is a herb that grows in North America (the USA and Canada).
It belongs to the same plant family as the buttercup.
Its scientific names are:
- actaea racemosa
- cimicifuga racemosa
It is also called:
- black snakeroot
- rattlesnake root
There is no scientific evidence that black cohosh can treat or prevent cancer.
Black cohosh is sold as a dietary supplement in health food shops and online. Manufacturers say that it can help reduce period cramps and discomfort. Many women use it to help with the symptoms and side effects of menopause, such as hot flushes.
Some women with breast cancer use black cohosh to help control menopause symptoms caused by their cancer treatment. But there isn’t enough scientific evidence to prove that this works. And we can’t be sure that it’s safe to take black cohosh after breast cancer treatment.
How you have black cohosh
Black cohosh comes as:
- capsules or tablets
- a powder
There is no standard dosage for black cohosh. A common German brand called Remifemin is used as a menopausal remedy. The suggested dose for this concentrated extract is between 15 and 30mg a day.
Other types of black cohosh may recommend that you take as much as 200mg a day.
Talk to your doctor before you have any type of complementary or alternative medicine. We do not recommend that you replace your conventional cancer treatment with any type of unproven therapy such as black cohosh.
Side effects of black cohosh
Side effects are rare with small to moderate amounts of black cohosh. Most studies have used black cohosh for less than 6 months, so we don’t know about its long term effects. We need more research to find out, and to be sure it's safe to have.
Common side effects are stomach pain, feeling or being sick, or skin rashes.
Very high doses (above 100mg) can cause:
- a slower heart rate
- lower blood pressure
- dizziness and light headedness
- womb (uterine) contractions
- joint pain
There have been a few reports of black cohosh seriously damaging the liver. While it is not clear whether black cohosh was responsible for the liver damage, the Medicines and Healthcare products Regulatory Agency (MHRA) say that all black cohosh products should carry a warning label.
Doctors worry that using black cohosh long term might cause the womb lining to thicken. This could lead to a higher risk of womb cancer. One study found that there was no thickening of the womb in women using black cohosh for 3 months.
Some research suggests that black cohosh can interfere with how some cancer drugs work. A review of studies in 2008 found this risk to be very small.
Research into black cohosh
We need more research to learn if black cohosh is safe to take and how it can help. Many of the studies so far have been small or were not controlled trials. A controlled trial is where a control group are given a dummy drug (placebo), and the researchers compare the results to a group having the new treatment.
Remifemin is a common brand of black cohosh. Some early clinical trials showed that Remifemin helped to relieve menopausal symptoms. Others showed that it didn't.
A review in 2005 found that black cohosh did appear to ease menopausal symptoms. Another review in 2008 looked at all the randomised controlled trials of black cohosh in women with menopausal symptoms. It seemed to work in some trials, but in others it didn't. The researchers suggested that more research is carried out to see whether black cohosh may work better for women at the beginning of their menopause.
There is currently no standard preparation of black cohosh. So the variation in trial results may be due to the differences in the type of black cohosh used.
A review in 2012 of 2,027 women, found there wasn't enough evidence to support the use of black cohosh for menopausal symptoms. They recommend more research to find out how black cohosh could affect the quality of life for menopausal women, their bone health and night sweats.
There is ongoing research to learn if black cohosh is a safe and helpful treatment for women who have, or have had, breast cancer.
Black cohosh might affect the body in a similar way to the hormone oestrogen. If it does, it might trigger breast cancer cells to grow, especially in women with the type of breast cancer that is affected by oestrogen (oestrogen receptor positive breast cancer).
However, more recent research suggests that black cohosh doesn’t cause oestrogen-like activity and behaves more like nerve signal transmitters. But we don’t know this for sure yet.
Studies looking at black cohosh for menopausal symptoms in women with breast cancer have had mixed results. Some show a benefit and others don’t. It is difficult getting accurate results because different amounts of black cohosh from different sources were used in the studies and they had different aims.
A Canadian study in 2007 found that black cohosh seems to be safe for women with breast cancer, as long as they don’t have liver problems. And a study in 2011 found that women taking the hormone therapy drug tamoxifen, who took black cohosh for 6 months, had fewer and less severe hot flushes.
Some laboratory studies have found that some of the active ingredients in black cohosh could interfere with how the body processes tamoxifen. As these studies were done on mice, it is difficult to know whether this risk applies to women.
At the moment there is no evidence to prove black cohosh can help prevent or treat cancer.
A 2007 study compared women who had taken black cohosh with women who hadn’t. It found that the women who had taken black cohosh were less likely to develop breast cancer. Another study found that women who took black cohosh had a slightly increased time before their cancer came back, compared to women who did not take black cohosh.
But these were small studies. We need more research before we can know if black cohosh can help to prevent breast cancer or stop it from coming back.
Black cohosh might have a harmful effect on areas of the body other than the breast. One study of mice in 2008 found that breast cancer was more likely to spread to the lung when they had black cohosh.
There is very early laboratory and animal research on the effects of black cohosh on prostate cancer cells.
Who shouldn’t take black cohosh
Black cohosh may not be safe or suitable for you to take. Black cohosh might interact with drugs you are having to treat cancer, blood pressure problems or liver disease.
Some doctors recommend that you shouldn’t take black cohosh for more than 6 months at a time.
Talk to your doctor first if you are thinking about taking black cohosh instead of hormone replacement therapy (HRT).
You shouldn’t take black cohosh if you:
- have breast cancer
- have liver problems
- are having some types of chemotherapy such as cisplatin
- have blood pressure problems or take medicines for your blood pressure
- are pregnant or breastfeeding
The cost of black cohosh
There are many black cohosh products. Prices vary depending on where you buy it and the dosage.
You can buy black cohosh remedies in health food shops, pharmacies or supermarkets. They are also available over the internet and from registered practitioners of Western herbal medicine.
The amount of black cohosh in each product can vary. Our advice is to be cautious.
Before having black cohosh
It is completely up to you to decide whether to use any alternative or complementary therapy. We recommend that you always check with your doctor before you start. That way, your doctor can have a full picture of your care and treatment.
A qualified herbal medicine practitioner can monitor your progress regularly and do some tests to make sure there are no harmful side effects. They also know when not to prescribe you a herb.
Relying on advice from staff in health food shops or information from the internet is very risky. The people involved in giving this advice often have little or no training.
Our advice is:
- Be careful.
- Check prices and the amounts each preparation contains.
- Make sure you look at all the information available.
- Talk to your cancer doctor before you buy or use any alternative or complementary therapy.
- Only use herbal medicine from a trained practitioner who is registered with a professional organisation.
- Only buy products that are registered under the Traditional Herbal Remedies (THR) scheme - these have been tested for quality and safety.
Phytotherapists (phyto means plant in Greek) are herbal practitioners with specialist university training. They combine medical knowledge and skills with a scientific understanding of plant medicines. The organisation provides information and has a list of practitioners in the UK.
9 Hythe Close
Tel: 01323 484353
CNHC is the UK regulator for complementary healthcare practitioners. It protects the public by giving them access to a list of practitioners who have met national standards of competence and practice. Registered practitioners can use the CNHC quality mark on certificates and publicity materials. Most NHS services only use CNHC registered practitioners.
46-48 East Smithfield
Phone: 0203 668 0406
The Memorial Sloan-Kettering Cancer Centre is a leading cancer hospital and research centre in New York. Its Integrative Medicine service was founded in 1999. It carries out research into the effectiveness of complementary therapies for cancer.
The website has a searchable database of herbs, vitamins and plants. It lists side effects, drug interactions, clinical information and clinical trials.
CAM-Cancer is a non-profit web resource that gives health professionals reliable information about complementary and alternative medicine (CAM) for cancer. It is managed by the Norwegian National Research Center for Complementary and Alternative Medicine (NAFKAM).