Safety of black cohosh

Summary

Black cohosh

There have been some questions raised about the safety of black cohosh, specifically with regards to liver damage and breast cancer. Overall, an examination of the evidence in the research journals, detailed below, will show that this herb is considered to be safe to use for peri-menopausal symptoms.

General evidence of safety of black cohosh use

In 2003, the Journal of the North American Menopause Society, Menopause, published two papers reviewing the safety of black cohosh. The first paper (a literature review) looked at black cohosh use in over 2,800 patients and concluded that black cohosh appears to be a safe option for women for the management of peri-menopausal symptoms.1 

The second paper concluded that the side effects from black cohosh are rare, mild and reversible. The most common side effects reported were digestive upsets and rashes.2  There were a few more serious side effects listed including thrombosis (blood clots), high blood pressure and slow heart rate. It concluded that the cause for these specific side effects could not be determined. An updated review also concluded that the evidence in research suggests that Black Cohosh is safe.i

Black cohosh and liver damage

In October 2002, in the Medical Journal of Australia, there was a single case report of a 47 year old Australian woman who developed acute hepatitis (inflammation of the liver) and as a result, needed a liver transplant.3  It was reported that this woman had been taking a black cohosh preparation for one week. The type of hepatitis that was observed in this woman was a severe immune reaction typical of a particular individual immune reaction and not because of a direct toxic injury.

The herbal product that was used was not analysed to show that the product did actually contain the herb black cohosh and therefore cannot conclude the herb as the cause of the liver damage.ii iii This has been the case for the majority of reports of black cohosh and suggested liver damage, and the source of much criticism from experts, raising serious doubts about the claims of the herb as a cause of liver damage.

After this first report, other authors started to suggest black cohosh as the cause of liver damage when a liver reaction was seen in a person who was taking the herb.

By 2006, there had been around 40 cases of suspected liver reactions due to black cohosh worldwide (69 cases by 2010), nine of which occurred in Australia. Of the Australian cases, four were hospitalised, with two requiring liver transplants.

This prompted the Australian Therapeutic Goods Administration (TGA) to issue a warning of the potential liver reaction from black cohosh, as they believed there was ‘sufficient evidence of a causal association between black cohosh and serious hepatitis’.4  As a result of this, labels of products containing black cohosh now read: ‘Warning: black cohosh may harm the liver in some individuals. Use under the supervision of a healthcare professional’.

The TGA more recently established an expert advisory group to review the existing regulatory controls on black cohosh. The expert group concluded that there appears to be an association between the use of black cohosh and liver damage, but it is very rare. They state that it was not possible to tell, with any certainty, the strength of the association, or any particular vulnerable group, type of preparation, dose, duration of use or specific products.

The expert group also determined that black cohosh is still suitable for use in complementary medicines, but recommended that the current warning statement on the medicine label be revised to better inform consumers about the risk and also to provide sufficient information to assist in the early detection of liver damage and, if detected, to seek medical attention.

The European Medicines Agency Committee on Herbal Medicinal Products (HMPC) also reviewed the evidence on black cohosh in a recent 2006 analysis (revised version January 2007). The HMPC analysed all the reports of liver reactions due to black cohosh. Eight international experts formed the group dealing with hepatotoxicity (liver toxicity). The report examined 15 clinical studies (between 1983 and 2005) and overall no case of significant liver dysfunction was reported. It was noted that long-term safety of black cohosh was not studied.

While the report overall demonstrated that there were only two cases where black cohosh was possibly related to liver damage the HMPC wanted to draw the attention of the public to the potential serious liver reaction that may occur in patients using products containing black cohosh. They offer the following advice:

Patients

Patients should stop taking black cohosh and consult their doctor immediately if they develop signs and symptoms of liver injury. Symptoms of liver disease can include:

Patients using herbal medicinal products should tell their doctor about it.

Several key factors need to be considered when looking at the evidence suggesting black cohosh as a cause of liver damage

In summary, while acute liver failure has been suspected with black cohosh, it is extremely rare and somewhat unpredictable.

Black cohosh and breast cancer

Of all the herbal medicines that a breast cancer survivor may consider using, black cohosh has the most research supporting its use and has the greatest amount of safety data. Studies have looked at whether this herb does have any oestrogen stimulating effects, which is an important factor for women with breast cancer. In vitro (test tube) studies using human breast cancer tissue and cell lines have demonstrated non- stimulatory or oestrogen-antagonist effects of Black Cohosh.iv v vi Furthermore Black Cohosh did not demonstrate any oestrogenic activity on several different breast cancer cell assays.vii New evidence suggests that the mechanism for relief of hot flushes may be due to the selective effects of Black Cohosh on the serotoninergic system and may not be due to oestrogenic properties.vii

There have been two clinical trials on black cohosh and breast cancer patients to date. In an open-label randomised clinical trial over 12 months, black cohosh reduced the number and severity of hot flushes in premenopausal (age 35-52) breast cancer survivors on Tamoxifen treatment.6  In a second study of only two months duration, black cohosh was no better than placebo (dummy treatment) for reducing number and intensity of hot flushes, in women with a history of breast cancer. More than two thirds of the women were on Tamoxifen in this study and possibly the shortness of the study limited the results.7  Interestingly, a study that looked at over 18,000 breast cancer patients, of which over 1,100 women had taken Black Cohosh, showed that after 2 years 14% of the women who did not take the Black Cohosh had a recurrence of breast cancer, whereas it took 6.5 years for women in the black cohosh group to reach this proportion.viii This is the longest study looking at the use of Black Cohosh in breast cancer patients and the first time that Black Cohosh has been suggested to have somewhat of a possible protective effect. Further studies are needed for more conclusive evidence.

A recent review of the research looking at black cohosh and its safety and effectiveness in cancer has supported the information above. While the effectiveness of the herb for treatment of symptoms is inconclusive, the report states that black cohosh has a relatively good safety profile, does not show phytoestrogen activity and the concerns about liver damage are inconclusive. The paper also states that there are no studies suggesting that black cohosh has a protective role in cancer prevention.8

The most important factor is to get the approval of the oncologist and breast specialist before commencing treatment with black cohosh. Of all the herbal medicines that a breast cancer survivor may consider using, black cohosh has the most research supporting its use and has the greatest amount of safety data. Longer trials of five years or more are needed to establish breast cancer safety data more conclusively. Black cohosh is only indicated for hot flushes, vaginal dryness and aches and pains and should only be taken for as long as symptoms persist.

References

  1. Low Dog, T. Powell, KL. Weisman SM. 2003 'Critical evaluation of the safety of Cimicifuga racemosa in menopausal symptom relief' Menopause 10 (4) pp 299-313
  2. Huntley, A. Ernst, E. 2003 'A systemic review of the safety of Black Cohosh' Menopause 10 (1) pp 58-64
  3. Whiting, PW. Clouston A. & Kerlin P. 2002 'Black Cohosh and other herbal remedies associated with acute hepatitis' MJA 177 pp432-435.
  4. www.tga.gov.au/cm/black Cohosh.htm
  5. Hudson, T. 2006. 'Black Cohosh Update: Does it work? Is it Hepatotoxic?' Altern & Compl med 12 (3) pp 132-135
  6. Munoz, GH. & Pluchino, S. 2003. 'Cimicifuga racemosa for the treatment of hot flushes in women surviving breast cancer', Maturitas 44 Suppl 1. pp S59-S65.
  7. Jacobson, JS. Troxel, AB. Evans, J et al., 2001. 'randomized trial of black Cohosh for the treatment of hot flashes among women with a history of breast cancer', J Clin Oncol 19(10), pp 2739-45.
  8. Walji R et al 2007, 'Black cohosh (Cimicifuga racemosa [L.] Nutt.): safety and efficacy for cancer patients.' Support Care Cancer Aug;15(8):913-21
    Content updated December 12, 2007

 

 

i. Borrelli, F. Ernst E. 2008. 'Black cohosh (Cimicifuga racemosa): a systemic review of adverse events'.Am J Obstet Gynecol 199(5):455-66.

ii. Teschke R. 2010 'Black Cohosh and suspected hepatotoxicity: inconsistencies, confounding variables, and prospective use of a diagnostic causality algorithm. A critical review' Menopause 17(5) 1088-9

iii. Vitetta, L. Thomsen, M & Sali, A. 2003. 'Black Cohosh and other herbal remedies associated with acute hepatitis' Letters to the Editor, MJA 178 pp 411-412.

iv. Amato, P. Christophe, S. Mellon, PL. 2002 'Estrogenic activity of herbs commonly used as remedies for menopausal symptoms.' Menopause 9(2) pp 145-50

v. Bodinet, C. Freudenstein, J. 2002 'Influence of Cimicifuga racemosa on the proliferation of estrogen receptor-positive human breast cancer cells' Breast Cancer Res Treat 76(1) pp 1-10

vi. Zierau, O. Bodinet, C. Kolba, S et al 2002 'Antiestrogenic activities of Cimicifuga racemosa extracts' J Steroid Biochem Mol Biol 80(1) pp 125-30

vii. Lupu R et al 2003, 'Black Cohosh, a menopausal remedy, does not have oestrogenic activity and does not promote breast cancer cell growth' Int J Oncol 23(5) pp 1407-12

viii. Zepelin, HH. Medan, H. Kostev, K et al 2007 'Isopropanolic black cohosh extract and recurrence-free survival after breast cancer' Int J Clin Pharmacol Ther 45(3): 143-54.