Soy's Menopause Benefits Questioned

Seems to Help Hot Flashes, But May Be Placebo Effect

From the WebMD Archives

Oct. 4, 2002 - Eat soy, eat flaxseed for hot flash relief, some experts say. But a new study finds that soy and flaxseed -- at least in muffin form -- don't do much good.

"Neither flaxseed nor soy significantly affected the women's quality of life," Jacqueline Lewis, MD, a researcher with the University of Toronto, tells WebMD.

She presented her paper at the 13th annual meeting of The North American Menopause Society held in Chicago this week.

In their study, Lewis and colleagues focused on 99 women -- all within one to eight years after menopause, all with vasomotor symptoms, such as hot flashes. They asked the women to eat soy flour, flaxseed, or wheat muffins daily for 16 weeks. Women kept track of what they ate each day, and had their urine tested weekly for isoflavones -- a sign that their bodies had absorbed and converted the soy and flax in their diet into estrogens the body can use.

While the women's urine showed high levels of isoflavones, there were no significant improvements in symptoms such as hot flashes, mood, or sexual function. Interestingly, over the 16-week period, all women showed increasing improvements -- whether they were eating placebo wheat muffins or not.

"But the overwhelming majority of data is in favor of soy," says Machelle Seibel, MD, a former professor at Harvard Medical School, now a reproductive endocrinologist and professor of clinical gynecology at the University of Massachusetts at Worcester.

He is also the author of the newly released book, The Soy Solution For Menopause.

While flax has been much discussed, but not studied, soy has been the subject of about 2,000 studies in the last seven years, he tells WebMD. "The effect on cholesterol lowering has been so great that the FDA approved claims that soy lowers cholesterol. In fact, soy and flax have shown a tendency to reduce menopausal symptoms by 45-50%."

Too often, researchers expect soy and other alternatives to create the effects of natural estrogen, says Seibel. "If you expect any alternative medicine to be exactly like estrogen, you're likely to be disappointed." Soy and flax are similar in their estrogen-like properties, but they are not as potent as estrogen, he says.


The complete absence of symptoms may not always be possible, Seibel says. "Women need reduction in symptoms, so quality of life is better, so they can get on with their lives."

And while a few small studies have pointed to a possible cancer risk from ingesting soy, he says that those data have been confusing at best. "I believe the data do not prevent women from taking soy even if they have breast cancer," he tells WebMD. "In fact, some studies find that soy helps prevent cancer." Whether soy is indeed a preventive is still being debated, he adds.

"The overwhelming majority of data favor soy," he says. "You don't need to eat that much -- 40-50 grams of soy protein a day -- a glass and a half of soy milk, half cup of soy nuts, a cup of tofu which you can make into various forms, such as chocolate mousse or as an additive to meat loaf."