Study Finds Soy Tablets Don't Ease Menopause Symptoms or Prevent Bone Loss

By Patricia Yollin on August 15, 2011

Women who use soy tablets to relieve the symptoms of menopause and prevent bone loss should stop because the pills simply don’t work, says Deborah Grady, founder and co-director of the UCSF Women’s Health Clinical Research Center.

Deborah Grady, MD

Deborah Grady, MD

“It’s just not a clinically important benefit,” said Grady, MD, MPH, who co-wrote a commentary on a study published Aug. 8 in the Archives of Internal Medicine.

The five-year randomize trial among 248 South Florida women found no significant differences between the 122 who took 200 milligrams of soy isoflavone tablets daily and the 126 who received a placebo. The research was an attempt to find an alternative to estrogen therapy, which prevents the hot flashes, night sweats, insomnia, vaginal dryness and rapid bone loss that often occur during menopause.

Many females have turned to soy because of concerns over the risks posed by estrogen treatment -- such as strokes, breast cancer and thromboembolism -- that are detailed in findings by the Women’s Health Initiative. The new study noted that Western women have significantly increased their consumption of soy products in the last decade because the soy-laden diet of women in Asia has been associated with a lower prevalence of breast cancer, osteoporosis and cardiovascular disease.

In addition to the findings of the Florida study, titled “Soy Isoflavones for Prevention of Menopausal Bone Loss and Vasomotor Symptoms,” Grady pointed out that a meta-analysis of 19 previous clinical trials determined that soy had little effect in mitigating hot flashes.

“This is the 20th trial,” said Grady, professor of medicine and associate dean for clinical and translational research at UCSF. “People probably need to consider this question answered.”

The women in the new study were ages 45 to 60, within five years of menopause, and with a bone mineral density T score of -2.0 or higher in the lumbar spine or total hip. Sixty percent were Hispanic. At the end of the research, 48.4 percent of women in the soy isoflavone group reported hot flashes, compared with 31.7 percent of women taking placebos, and more women in the soy group also suffered from constipation.

Silvina Levis, who led the study and is director of the Osteoporosis Center at the University of Miami Miller School of Medicine, told the Miami Herald the results were “disappointing” but not “surprising.” Grady was equally unsurprised.

“The results in the past have been mixed but primarily negative,” Grady said. “This is an important study. It was an-NIH funded study. It’s a big study. It’s one of the most methodologically sound. They used a large dose of soy. People who are enthusiastic about soy complained in the past that studies didn’t use enough soy or the right kind of soy.”

She said dietary soy has been used in several studies, so it’s not a question of whether eating tofu or edamame might be more effective than taking pills: It didn’t make any difference. As for why Asian women fare better in terms of osteoporosis and the symptoms of menopause, Grady said it is still a mystery but added, “Their genetics are quite different.”

Targeting Specific Menopause Symptoms

So what is a woman to do?

“We should put our effort into new and innovative therapies and stop beating this old horse,” said Grady.

Black cohosh and other alternative therapies, she said, have also not proved effective.

In the commentary that Grady and Seattle researcher Katherine Newton, PhD, were invited to write for the Archives, they said, “Perhaps efforts should be directed away from the hope of a one-size-fits-all therapy for menopausal symptoms toward using existing treatments to target the symptoms that disturb patients most.”

Targeting specific symptoms could take the form of antidepressants for women who suffer from depression, Grady said, or anti-insomnia drugs for women who can’t sleep.

Eighty percent of menopausal women experience hot flashes and night sweats, and 20 percent are uncomfortable enough to seek treatment. About 10 million in the United States are currently using post-menopausal hormone therapy, which Grady estimated is a 50 percent drop from a decade or so ago.

Grady said women with mild hot flashes can resort to environmental solutions such as dressing in layers or keeping the window open. For mild-to-moderate episodes, some non-estrogen treatments such as selective serotonin reuptake inhibitors or gabapentin can have modest effects. In severe cases, hormones are the most effective treatment.

“I wish there were some alternatives that are as effective, but there aren’t,” Grady said. “So that leaves us with hormone therapy, but at the lowest dose that makes the woman comfortable. Estrogen is a great treatment for bad symptoms, but when the symptoms go away, a woman should reduce the dosage or stop. If you had a headache, you wouldn’t take four aspirins if you only needed two.”

Grady hopes the study will dissuade women from taking concentrated soy supplements because she said the doses are artificially high and there isn’t much long-term data on safety.

“But if women want to increase the soy in their diets, that’s fine,” she said. “It’s perfectly safe. It’s hard to get too much soy just in dietary intake.”

Grady and Newton said the study had one noteworthy shortcoming: Only 248 of an expected 306 participants were enrolled, and dropout rates higher than anticipated led to a much lower final sample size than predicted. The results of the control and soy groups were so similar, however, that they didn’t think it mattered.