Last Updated: 2003-06-02 12:59:49 -0400 (Reuters Health)

NEW YORK (Reuters Health) - Advised to avoid hormone replacement therapy, breast cancer survivors often look to herbal remedies that contain estrogen-like chemicals called phytoestrogens to quell menopausal hot flashes.

But these plant-derived substances are no more likely than a placebo to cool hot flashes, according to a study published in the June issue of Obstetrics and Gynecology.

In theory, phytoestrogens would seem to be the perfect choice for breast cancer survivors, according to the new study's lead author, Dr. Eini Nikander, a researcher in the department of obstetrics and gynecology at Helsinki University Central Hospital in Helsinki, Finland.

That's because the estrogens from plants don't bind well to receptors in the uterus, breasts or ovaries, Nikander said in an interview with Reuters Health.

But they do lock on to estrogen receptors in a variety of other spots in the body, including the brain and the bones.

"That's why they shouldn't have, at least in theory, much effect on breast cancer cells," Nikander said.

For the new study, Nikander and her colleagues followed 56 women who had been treated for breast cancer. The women were randomly assigned to either a group that received phytoestrogens or one that received placebo tablets.

After three months the groups received no therapy for two months and then switched treatments for the next three months.

During the study, the researchers interviewed the women about menopausal symptoms, including hot flashes.

When the researchers compared the effects of placebo and phytoestrogen on menopausal symptoms, they found no difference.

Some might argue that it takes longer than three months for phytoestrogens to quell hot flashes, Nikander said. But traditional hormone replacement therapy improves hot flashes within days, she added.

The new results leave breast cancer survivors with few choices to help them deal with menopausal symptoms.

"The only healthy alternatives are less alcohol, stress and coffee and more sleep and exercise," Nikander said.

Nikander said that some medications may relieve hot flashes in some women, including beta-blockers and antidepressants called SSRIs, or selective serotonin reuptake inhibitors. SSRIs include Paxil (paroxetine), Prozac (fluoxetine) and Zoloft (sertraline).