Because of the limited understanding of why Black Cohosh helps menopausal women, the prestigious National Institute of Health is financing a thorough study of the plant through its subsidiary the National Center for Complementary and Alternative Medicine (NCCAM). It is hoped that this research will provide solid information about the short and long-term efficacy as well as potential dangers of Black Cohosh supplementation. Others are concerned about Black Cohosh's potential of accelerating the spread of breast cancer cells, a fear founded on the results of a test done on lab mice. As of yet, people using the herb have only reported minor problems such as headaches, stomach discomfort, and dizziness at higher doses.
Short term use of Black Cohosh, specifically for periods no greater than six months, was endorsed by the American College of Obstetricians and Gynecologists in 2001. This is because limited use of the herb diminishes symptoms of menopause without any apparent danger. They recommended a Black Cohosh extract.

Another research found that black cohosh can cause the body's immune system to launch an attack on the liver, doctors warn. Stanley M. Cohen, MD, assistant professor of medicine at the University of Chicago, tells that he and colleagues have diagnosed what they believe is the first case of autoimmune hepatitis caused by the use of black cohosh.

A progressive inflammation of the liver, caused by the body's immune system, attacks the liver cells. Some patients complain of abdominal discomfort, others of achy joints and itching. The skin may become yellow, and the liver can become enlarged. The disease is thought to have some genetic link, with women accounting for as many as 70% of the patients.

It is not clear at this point whether black cohosh stimulates the growth of breast cancer cells or inhibits their growth; research to date has been limited and has produced mixed results. Women with a history of breast cancer, therefore, and those at a high risk for developing breast cancer (for example, a strong family history like a mother or sister with breast cancer) should not take black cohosh without talking to a healthcare provider.

Pregnant and breastfeeding women should avoid black cohosh as the herb may stimulate contractions and lead to premature labor.

Some individuals taking high doses of black cohosh have reported side effects including abdominal pain, diarrhea, dizziness, headaches, joint pains, nausea, slow heart rate, tremors, visual dimness, and vomiting.

Tip:
The use of black cohosh is a time-honored approach to strengthening the body and treating disease. It, however, contain active substances that can trigger side effects and that can interact with other herbs, supplements, or medications. For these reasons, black cohosh should be taken with care, under the supervision of a practitioner knowledgeable in the field of botanical medicine.