Soy Preparations Not the Holy Grail For Controlling Hot Flashes

Soy No Better Than Placebo for Menopausal Symptoms, Researchers Find

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March 7, 2000 (Lake Worth, Fla.) - Soy preparations do not seem to be the long-sought Holy Grail for controlling menopausal symptoms, particularly hot flashes, a new study shows. The study, from the Mayo Clinic in Rochester, Minn., compared soy tablets against a placebo (sugar pill) and found little difference in hot flash frequency or severity.

"We saw preliminary data, lots of lay information, and lots of excitement about soy being helpful," Charles L. Loprinzi, MD, tells WebMD. "We tried to set up something to try and prove that it would be beneficial and we found out there was no suggestion whatsoever of any benefit." Loprinzi, one of the study authors, is professor and chairman of the division of medical oncology at the Mayo Clinic, where the study was done. The study is reported in the Journal of Clinical Oncology.

The popularity of soy supplements was evident when the researchers had 160 volunteers enter the trial within two months of announcing it. The soybean contains phytoestrogens, which are plant-derived estrogens that are like human estrogens but much weaker. Many thought they might have a similar effect.

The researchers divided women into two groups. Group 1 took four weeks of soy estrogen therapy followed by four weeks of placebo therapy. Group 2 did just the opposite. The women never knew which pills they were given at any time. The participants were asked to keep a record of their hot flash intensity and frequency. At the end of the trial they were asked which four-week regimen they felt worked best for them.

The soy estrogen regimen proved to be no better than the placebo. In fact, 36% of the patients who received the placebo reported that hot flash frequency had been cut in half, compared to 24% of those who received the soy.

The women in the study were given 150 mg of soy estrogens per day, the equivalent, Loprinzi says, of three eight-ounce glasses of soy milk.

"It didn't show whether soy protein was helpful in preventing [bone loss or] what effect it had on the breast or [uterus], " Steven Sondheimer, MD, tells WebMD. "This study doesn't answer a lot of other questions [but] it is helpful for the patient who is considering using soy proteins for her hot [flashes]."


Many women, particularly those who have a family history of breast cancer, or who have had breast cancer, seek alternatives to estrogen replacement therapy as a way to control menopausal symptoms because they have concerns that it may promote the disease.

Scott M. Eisenkop, MD, says this interest in plant estrogens grew from a sort of "antimedicine" element of society and through media emphasis on natural estrogen. He says the concern that estrogens may cause breast and other cancers added to soy estrogen's popularity, even though this thinking is controversial. "It's probably more beneficial to give it [estrogen] than not to give it," he tells WebMD.

However, for the woman who does not wish to take estrogens, Loprinzi says there are some alternatives. "Vitamin E works a tiny bit, decreasing about one hot flash per person per day, clonidine cuts hot flashes 20% more than does a placebo, but has side effects such as light-headedness and constipation, and megestrol acetate will decrease hot flashes by about 80%," he says. Currently, Loprinzi is conducting a trial to see if some of the newer antidepressants work and will present this information at an oncology conference in May.

Because soy preparations are readily available in health, drug, and grocery stores, Sondheimer says if a patient wishes to see if it will help her symptoms, it's not inappropriate to prescribe it, "[as long as] the patient understands clearly that it has not been shown to be better than a placebo."

Vital Information:

  • Soy contains phytoestrogens, which are similar to human estrogen. There is much speculation about the benefits of soy in controlling symptoms of menopause.
  • New research shows that taking soy supplements does not seem to reduce hot flashes among menopausal women, but other symptoms were not examined.
  • For women seeking relief from hot flashes, alternatives to estrogen include vitamin E, clonidine, and megestrol acetate.
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