Study Disproves Soy as Aid in Fighting Hot Flashes

February 29, 2000

New York (MedscapeWire) Feb 29 Despite advertisements touting the powers of soy to stop or decrease hot flashes in women, a study by the North Central Cancer Treatment Group Clinic (NCCTG) based at the Mayo Clinic in Rochester, Minn, has found that cancer survivors who took soy pills did not experience any noticeable changes. The study is published in the March 1 issue of the Journal of Clinical Oncology.

"Despite optimistic hopes that this soy phytoestrogen product would alleviate hot flashes, the scientific data from this study demonstrated that it did not help," said Charles Loprinzi, MD, a Mayo Clinic medical oncologist and one of the authors of the study. "Thus, we need to explore other means for alleviating hot flashes in women who choose not to use estrogen or progesterone preparations."

Susan Quella, principal investigator of the study and nurse coordinator for the NCCTG, said the study originated after seeing numerous advertisements that include claims about the benefits of soy, without any science behind the assertions.

"There really hadn't been much scientific testing of this, but we see advertisements that tout the wonders of soy, and many people are turning to this and a variety of herbal and natural remedies without any real study of whether it does what they say," Quella says.

Researchers started their randomized, double-blind study of female breast cancer survivors in March 1998, reporting data regarding 177 patients who entered this study.

One half of the study's participants received the soy pills for 4 weeks while the other half received placebo. Each group switched regimens after 4 weeks and completed another 4 weeks under the new regimen. Participants kept detailed diaries on their reactions each day.

The soy product that study participants consumed had 50 milligrams of soy isoflavones in each tablet. Patients were instructed to take 1 tablet 3 times a day, which would result in 150 milligrams of isoflavones per day, an amount similar to what would be consumed with 3 glasses of soy milk.

Soy contains phytoestrogens, weak estrogen-like substances in the soybean that some believed would bind to estrogens to abrogate hot flashes.

Hot flashes can be a very significant symptomatic complaint for women experiencing diminished ovarian function as a result of menopause, or breast cancer treatment with cytotoxic chemotherapy drugs, or the anti-estrogen tamoxifen citrate.

Hot flashes are described by clinicians as a transient episode of flushing, sweating, and a sensation of heat, often accompanied by palpitations and a feeling of anxiety, and sometimes followed by chills. Hot flashes can be very disruptive to life. Patients describe anxiety-producing hot flashes with sweat requiring changes of clothing and bedding, disruption of sleep, and a general diminishment of mental and physical quality of life.

Many women reject hormone replacement therapy due to concern that estrogen might promote breast cancer. Women being treated for breast cancer often are prescribed tamoxifen. Tamoxifen is a drug that interferes with the effects of estrogen on breast tissue and has been shown to decrease the risk of breast cancer recurrence. However, this anti-estrogen action may increase hot flashes.

"For now, we have to move on and find things that work for patients," says Quella. "NCCTG is committed to study untested substances that are becoming popular with the public."


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