Soy Preparations Not the Holy Grail For Controlling Hot Flashes
Soy No Better Than Placebo for Menopausal Symptoms, Researchers Find
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]."