Assessing black cohosh
When warnings first emerged two years ago about the safety of taking hormones for menopausal symptoms, many women began turning to alternative treatments, such as herbs, for relief.
Now researchers are asking whether the most common of those herbs, black cohosh, is any safer.
A plant native to North America, black cohosh has long been an American folk remedy for menopausal discomforts such as hot flashes. But with the recent, increased interest in non-drug therapies, it’s now thought to be used by millions of women. Because the herb is natural, many women believe it’s completely safe, ultimately taking it for months or years, experts say.
Although small studies have indicated that black cohosh is effective for use up to six months, many of those studies weren’t considered to be rigorous, scientific research. Little data exist on the safety of long-term use, and some research has even suggested the herb may pose health risks.
“As far as we know from short-term studies, it appears safe,” said Dr. Paula Amato, an assistant professor of obstetrics and gynecology at Baylor College of Medicine. “But experience with other herbs has shown that it’s often only when herbs become widely used that [safety problems] begin to show up.”
Several government-funded studies now underway may supply much-needed information on the potential benefits and risks of black cohosh. Because the herb is a dietary supplement, manufacturers don’t need to prove its safety or efficacy before marketing.
“This herb has been used for thousands of years,” says Dr. Ed Sauter, associate professor of surgery at the University of Missouri, Columbia. “We need to understand how it works. That is key. The only way we’ll do that is by clinical trials.”
Sauter is conducting one of several studies on black cohosh funded by the National Center for Complementary and Alternative Medicine. In his study, 73 healthy menopausal women will take the herb for three months. The women’s symptoms will be assessed and tests will be run on blood and breast fluid samples.
The study’s primary goal is to determine how black cohosh works. Some studies have suggested the herb acts similarly to estrogen to relieve symptoms. (Hot flashes are blamed on a decline in estrogen that occurs at menopause.) Other studies, however, suggest the herb does not act like estrogen.
“There is a lot of anecdotal evidence that women get relief,” Sauter says. “We want to find out, first of all, is that true. And then how. What provides the relief of symptoms is unknown. The real knowledge base is extremely limited.”
It’s possible, he says, that black cohosh works in the brain to reduce hot flashes (similar to certain antidepressants that appear useful in treating menopausal symptoms) or via some other mechanism.
The tests of blood and breast fluid should yield clues to the herb’s pathways in the body. Researchers will be able to detect changes in various hormone levels, for instance.
Despite the general belief that the herb is safe, not all scientists or doctors are convinced.
A few cases of liver toxicity have been reported in women taking the herb. And a study presented at a scientific symposium last year showed that breast cancer was more likely to spread to the lungs of mice given black cohosh. If the herb acts like estrogen, long-term use could adversely affect uterine or breast tissue, according to the National Institutes of Health.
Some doctors advise women who have had breast or uterine cancer to avoid the herb until more is learned. But women who have had breast cancer often take the cancer-prevention drug tamoxifen, which can lead to particularly severe hot flashes. Such women are the ones most likely to need black cohosh.
“Women are obviously concerned about whether it works or not, but they don’t always consider the possibility that it might be harmful,” Amato says.
In March, a consumer health watchdog group, Center for Science in the Public Interest, submitted a letter to the Food and Drug Administration citing reports of adverse effects and asking the agency to issue a consumer advisory about the herb’s possible risks. The FDA has not commented other than to acknowledge receipt of the letter, says David Schardt, senior nutritionist with the organization.
Women taking the herb shouldn’t be frightened by these reports, Sauter says. “There is no clear-cut evidence that should raise concern,” he says.
The herb appears safe enough to study it in women with breast cancer, says Dr. Barbara A. Pockaj, a researcher at Mayo Clinic Scottsdale who is the principle investigator of a study underway at 13 medical centers. The study is funded by the National Cancer Institute.
“New data shows that black cohosh is ... a natural antidepressant, like Effexor or Prozac,” said Pockaj in an e-mail. “Due to the fact we have not seen any deleterious effects in women and breast cancer who are on antidepressants, we do not feel that black cohosh carries any additional risk.”
Sauter says he’s concerned that some of the black cohosh products on the market are unreliable. His studies have found that the chemical components can vary from capsule to capsule.
In addition to Sauter’s and Pockaj’s studies, the federal government is funding five studies that look at safety and efficacy. One addresses the effects of the herb on the uterus and another looks at black cohosh in menopause along with another herb, red clover. The government’s interest in black cohosh is appropriate, Schardt says.
“It’s good that there is some research being done,” he says. “There are some red flags that have been raised about black cohosh and we have to make sure we know what we’re doing.”
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Black cohosh
Used for menopausal symptoms such as hot flashes, vaginal dryness, moodiness and fatigue. Appears safe and effective for use up to six months. However, randomized, controlled studies on the herb are lacking.
Can cause some gastrointestinal discomfort in some women.
Appears safe for use with other herbs or medications. However, it may interact with the cancer-prevention drug tamoxifen.
The typical dose is 20 to 40 milligrams twice a day. Usually sold in capsules but tinctures are also available.
Costs about $20 a month for a 20-milligram, twice-daily dose.
Source: American Family Physician
