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Black
cohosh may reduce hot flashes by targeting brain's thermostat
Eurekalert,
September 07, 2003
NEW YORK, Sept. 7 — Black cohosh, a medicinal herb increasingly used by women as an alternative to estrogen replacement therapy, may reduce hot flashes by targeting serotonin receptors — some of the same receptors used by the brain to help regulate body temperature — according to a team of researchers from the University of Illinois at Chicago. The finding, the first to demonstrate a possible mechanism of action for the herb other than estrogen, increases the likelihood that the herb is safe to use, they say. The
study was described today during a press briefing on hormone replacement
therapy at the 226th national meeting of the American Chemical Society,
the world's largest scientific society. The study also will appear in the
Sept. 10 print issue of the Society's Journal of Agricultural and Food
Chemistry. Until
now, many scientists thought that black cohosh (koh-hawsh) worked by
targeting receptors for estrogen, the same hormone used in commercial
hormone replacement medicine that has recently been associated with
adverse side effects, including breast cancer and stroke. "This
study shows that black cohosh does not appear to be estrogenic whatsoever
and, as a result, is less likely to pose some of the dangers associated
with traditional estrogen replacement therapy," says study leader
Judy L. Bolton, Ph.D., a professor at the university's College of
Pharmacy. "We now have new clues to how it might work in the
body." Although
preliminary evidence of the herb's efficacy in relieving hot flashes,
night sweats and other symptoms of menopause is encouraging, further
studies are still needed before it can be recommended, Bolton says.
Long-term safety data on black cohosh is also needed, she adds. To
determine whether black cohosh is estrogenic, the researchers used a group
of rats whose ovaries had been removed. The rats were divided into
different groups and each group was fed a different concentration of
cohosh extract daily for two weeks. Extracts of the herb, either alone or
in combination with synthetic estrogen, did not produce any changes in
uterine weight or vaginal cell differentiation in the animals. This
indicates that the herb has no estrogenic effects, the researchers say. In
accompanying lab studies, the researchers also demonstrated that the black
cohosh extract is capable of binding to human serotonin receptors,
including those that help regulate body temperature. Previous studies have
shown that these receptors may play a role in regulating hot flashes.
Antidepressant medications, which some people believe may help reduce hot
flashes, also bind to the same receptors. The current study may help
provide an explanation for this effect, Bolton says. Researchers
still do not know the specific chemical or chemicals in black cohosh that
target the serotonin receptors. Nor do they know if the herb may target
hot flashes via additional mechanisms. Further studies are underway to
find answers to these questions, they say. A
Phase II clinical trial involving women with a high frequency of hot
flashes is now underway at the university to determine whether black
cohosh actually reduces the frequency and intensity of hot flashes and
other menopausal symptoms. The women will either receive black cohosh, red
clover, a placebo or estrogen replacement during the one-year trial, which
is one of the largest and longest of its kind, according to Bolton. The
trial is funded by the National Institutes of Health. Black cohosh is
indigenous to North America and is used by many women to treat menopausal
problems. Native Americans originally used it to treat a variety of
ailments, including gynecological disorders and even depression. Interest
in the herb has soared following the recent findings of the Women's Health
Initiative study, which showed that the health risks of estrogen
replacement therapy, including breast cancer and stroke, might outweigh
its benefits for some women. ### Editor's note: The press briefing on hormone replacement therapy is
scheduled for 2 p.m., Sept. 7, at the Javits Convention Center, Room 1B04,
in New York.
Judy
L. Bolton, Ph.D.,
is a professor in the Department of Medicinal Chemistry and Pharmacognosy
in the College of Pharmacy at the University of Illinois at Chicago. The
online version of the paper cited above was initially published July 29 on
the journal's Web site. Journalists can arrange access to this site by
sending an e-mail to newsroom@acs.org
or calling the contact person for this release. Copyright
© 2002 Global Action on Aging
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