Black cohosh

Black cohosh is a herb. It belongs to the same plant family as the buttercup and grows in North America (the USA and Canada). It is also called black snakeroot, rattlesnake root or squawroot. Its scientific names are

• Actaea racemosa
• Cimicifuga racemosa

Available scientific evidence does not support claims that black cohosh is effective in treating or preventing cancer.

You can buy black cohosh as a dietary supplement in health food shops and online. Manufacturers say that it can help to reduce the cramps and discomfort women may have just before and during a period. Many women also use it to help with the symptoms and side effects of menopause, such as hot flushes. Some researchers say that it seems to have oestrogen like effects on the body.

Some women with breast cancer use black cohosh because they believe it will help to control symptoms of menopause caused by their cancer treatment. There isn’t enough scientific evidence to prove this. And we can’t be completely sure it’s safe to take black cohosh after breast cancer treatment.

Some people claim that taking black cohosh may help treat cancer or reduce your risk of getting breast cancer or prostate cancer. There is not enough scientific evidence to support this. We need more research to find out if it works, and if it is safe to take.

If you are interested in using black cohosh or any other type of complementary or alternative medicine, always talk to your doctor first. We don’t recommend that you replace your conventional cancer treatment with any type of unproven cancer therapy such as black cohosh. Some studies suggest it might interfere with some cancer drugs such as chemotherapy or hormonal therapy. The safety of long term use is not known.

Black cohosh comes as

• Capsules
• Tablets
• A powder
• Liquid
• Tincture

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 is between 20 and 40mg, twice a day.

Other types of black cohosh may recommend that you take as much as 200mg a day.

Side effects are rare with small to moderate amounts of black cohosh. The most common side effect is feeling or being sick. But very high doses (above 100mg) can cause

• A slowing of your heart rate
• Headaches
• Dizziness and light headedness
• Womb (uterine) contractions
• Joint pain

There have been a few reports of black cohosh seriously damaging the liver. Although it is not clear whether black cohosh was responsible for liver damage in these reports, the Medicines and Healthcare products Regulatory Agency (MHRA) say that all black cohosh products should carry a warning label.

Doctors are worried that using black cohosh long term may cause thickening of the womb lining. This could lead to an increased risk of womb cancer. One study found that there was no thickening of the womb in women using black cohosh for 3 months. But we need more research to find out exactly what the long term effects are and if it is safe to take.

Some research suggests that black cohosh can interfere with how some cancer drugs work, such as chemotherapy or hormone therapy.

Several published clinical trials have looked at the safety of black cohosh and how well it works. Many of the trials weren’t controlled trials and were small. There is information below on

• Controlling menopausal symptoms for women in general
• Controlling menopausal symptoms caused by breast cancer treatment
• Preventing or treating cancer

Controlling menopausal symptoms for women in general

Most trials have used the German brand of black cohosh called Remifemin. Some early clinical trials showed that Remifemin helped to relieve menopausal symptoms and others showed that it didn't.

It seems that it is more likely to help with mild symptoms. And it is likely to work better in women whose symptoms have only just begun rather than women who have been menopausal for some time.

A systematic 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 past their menopause women and again found that in some trials it seemed to work and in others it didn't. They suggest that research is carried out to see whether it may work for women at the beginning of their menopause. Currently there is no standard preparation of black cohosh and so the variation in trials may be due to the differences in the type of black cohosh used in the studies.

Controlling menopausal symptoms caused by breast cancer treatment

We don’t know whether black cohosh is safe to take if you have, or have had, breast cancer. It may affect the body in a similar way to oestrogen. If it does, this might trigger breast cancer cells to grow, especially in women with oestrogen receptor positive breast cancer. The latest research suggests that black cohosh doesn’t cause oestrogen like activity, but we don’t know this for sure yet.

Studies looking at black cohosh for menopausal symptoms in women with breast cancer have had contradictory results. Some show a benefit and others don’t. A systematic review in 2002 found that black cohosh didn’t reduce hot flushes. A more recent study in 2003 looked at giving it to women who were taking tamoxifen. This showed that it may reduce hot flushes. A study in Canada in 2007 reviewed 5 clinical trials. They found that black cohosh seems to be safe for women with breast cancer, as long as they don’t have liver problems.

Results of previous studies are difficult to interpret because different amounts of black cohosh from different sources were used and they had different aims. We need more research to tell us if black cohosh is really a safe and helpful treatment for women with breast cancer. An American study (funded by the National Center for Complementary and Alternative Medicine - NCCAM) is underway to find out more about the effects of black cohosh on menopausal symptoms.

Some laboratory studies have found that some of the active ingredients in black cohosh could interfere with how the hormonal therapy tamoxifen is processed in the body. But these studies were done on mice, so it is difficult to know whether this risk applies to women on tamoxifen who take black cohosh.

Preventing or treating cancer

Some people have claimed that black cohosh may reduce your risk of getting breast cancer or prostate cancer. There is not enough evidence for this at the moment.

An American study published in 2007 compared women who had taken black cohosh with women who hadn’t. They found that the women who had taken black cohosh were less likely to develop breast cancer. But this is only one study. We need more research before we will know if it can help to prevent breast cancer. Another study in 2007 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 this is a very small study. One study in mice in 2008 found that breast cancer was more likely to spread to the lung when the mice were given black cohosh. So black cohosh may have a harmful effect on areas of the body other than the breast.

Researchers are looking at the effects of black cohosh on prostate cancer cells in the laboratory and in animal studies. These are very early studies. Even if the results are positive, we will need more research before we can tell whether black cohosh can prevent prostate cancer.

Some doctors recommend that you shouldn’t take black cohosh for more than 6 months at a time. People who have liver problems should not take it because it can damage the liver. You also shouldn’t take black cohosh if you

• Have breast cancer
• Are having chemotherapy - studies show that some chemotherapy drugs may not work as well if you take black cohosh
• Have blood pressure problems or take medicines for your blood pressure
• Are pregnant or breast feeding

If you are thinking about taking black cohosh instead of hormone replacement therapy (HRT), always talk to your doctor first. Black cohosh may not be safe or suitable for you to take.

Black cohosh may also interact with drugs to treat blood pressure disorders and those for liver disease.

You can buy black cohosh remedies

• In health food shops
• From registered practitioners of Western herbal medicine.
• In pharmacies
• Over the internet

There are many black cohosh products. Prices vary depending on where you buy it and the dosage. The amount of black cohosh in each product can vary. Our advice is to be cautious.

You can find more information about searching for complementary and alternative therapies on the internet in our about complementary therapy section.

You will of course make your own decision about taking any alternative or complementary therapy. We recommend that you always check with your doctor before you start using any of them. That way, your doctor will always have the full picture about your care and treatment. Find out all you can about any therapy before deciding to use it. Look in our about complementary therapy section for more information about telling your doctor if you are using any complementary therapy.

Our message 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

We recommend that you use herbal medicine from a trained herbal medicine practitioner registered with a professional body such as the National Institute for Medical Herbalists or the College of Practitioners of Phytotherapy. The Complementary and Natural Healthcare Council (CNHC), supported by the Department of Health (DoH), also maintain a register that all complementary therapy practitioners can join.

A herbal medicine practitioner will monitor your progress regularly and do simple liver function tests to check that there are no side effects from the prescriptions. And they also know when not to prescribe a herb. Relying on advice from staff in health food shops and the internet is very risky as the people involved in giving advice have little, or no, training.

Our section about complementary and alternative therapies is a useful place to start for general information about complementary and alternative therapies in cancer care.

The following UK organisations give information specifically about herbal medicines.

The National Institute for Medical Herbalists
Elm House
54 Mary Arches Street
Exeter
EX4 3BA
Tel: 01392 426022
Email: info@nimh.org.uk
Website: www.nimh.org.uk

Gives information about western herbal medicine and also has a register of UK herbal medicine practitioners.

The College of Practitioners of Phytotherapy
Oak Glade
9 Hythe Close
Polegate
East Sussex
BN26 6LQ
Tel: 01323 484353
Email: pamela.bull@phytotherapists.org
Website: www.phytotherapists.org

Phytotherapists (‘phyto’ means ‘plant’ in Greek) are dedicated 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 preactitioners in the UK.

You can find information about black cohosh on the following websites

The Memorial Sloane Kettering Integrative Medicine website has information on many types of herbs and dietary supplements. It also evaluates alternative or unproven cancer therapies.

The NHS Complementary and alternative medicine specialist library has evidence based information about complementary and alternative therapies.

The CAMEOL database is a joint project between the Research Council for Complementary Medicine and the University of Westminster. It evaluates complementary medicines.

The Complementary and Natural Healthcare Council aims to enhance public safety, by giving the general public access to a list of practitioners that have been independently assessed as meeting national standards of competence and practice.