Black cohosh is generally considered safe, and clinical studies did not report significant side effects.
The administration of standard or high doses of black cohosh over 3–6 months does not appear to impact liver function. Likewise, black cohosh shows no significant effects on blood pressure, heart rate, body weight, or body mass index (BMI). Studies have also explored its impact on kidney function, total cholesterol, and triglycerides, revealing no overall effects except for a few studies reporting instances of increased high-density lipoprotein (HDL) cholesterol and decreased low-density lipoprotein (LDL) cholesterol.[1] Furthermore, trials comparing black cohosh to tibolone (a medication used to treat menopausal symptoms) found that people taking black cohosh exhibited fewer side effects (e.g., vaginal bleeding, spotting) than those taking tibolone.[1][2]
One meta-analysis indicated that 0.5% to 15% of menopausal women taking black cohosh experienced gastrointestinal discomfort.[3]
One animal study, coupled with in vitro testing on human cells, found that both in rats and in vivo black cohosh induced micronuclei (MN), which are biomarkers of genetic alterations, while also disrupting the folate pathway. This disruption led to non-regenerative macrocytic anemia in rats, characterized by enlarged red blood cells and inadequate bone marrow red blood cell replacement. Although these results indicate a potential risk associated with taking black cohosh, clinical studies are required to examine the impact on the human body.[4]