Does Soy Help With Hot Flashes? A New Study Says No, But….

Recently, the disappointing results of a study that looked into the effectiveness of soy and fiber as natural remedies for hot flashes and night sweats were published, reminding us once again that few non-hormonal treatments for vasomotor and other menopause symptoms work with any consistency.

In this most recent study, researchers followed 1651 women for ten years, and based on survey responses and annual visits, they concluded that there was no consistent association between the consumption of soy or fiber and the incidence of hot flashes. But there’s encouraging news elsewhere for those women who can’t or don’t want to take hormone therapy for their hot flashes.

Because soy is a phytoestrogen that has both pro-estrogen and anti-estrogen effects, it is the most studied of the botanicals for menopause-related conditions. Hundreds of clinical trials have yielded rich data to learn from. However, there are so many inconsistencies among these studies, such as dosing, age of participants, frequency of flashes etc., that it’s a challenge for researchers to draw definitive conclusions in a meta-analysis.menopause, hot flashes, soy isoflavones

So, two years ago, the North American Menopause Society (NAMS) convened a working group of clinical and research experts in the fields of women’s health and botanicals to review available, worldwide scientific data on risks and benefits of soy products (whole soybean, soy protein, soy germ) in menopausal health, and to identify areas for further research. A report based on their conclusions was issued the following year and this Fall, at the recent NAMS annual conference, I listened as Dr. Tara Allmen, a member of the task force, explained the panel’s findings to her physician-colleagues.

Of the many studies conducted over the years, the group selected only 14 to review. They were chosen for their consistency of influencing factors including; dose of soy isoflavones, mean age of the study participants, magnitude and frequency of the women’s flashes, treatment duration of at least 12 weeks and patient population who had experienced natural (not induced) menopause. Dr. Allmen, a national certified menopause practitioner (NCMP) at the Center for Menopause, Hormonal Disorders and Women’s Health in New York City, reported that “of the 14 studies, 11 showed a significant improvement of vasomotor symptoms as compared to placebo, especially in women having four flashes a day.” Three trials failed to show any benefit. As summarized in the NAMS Isoflavones Report, other results of the 14 trials included:

  • The percentage of decrease in daily frequency of hot flashes ranged from 24% to 60%.
  • The dose of 50 to 60 mg/day was sufficient for significant symptom improvement over placebo in many of the studies.
  • Women experiencing more than four daily hot flashes did not necessarily show greater improvement over placebo.
  • Trial duration of 12 weeks was sufficient to see a benefit in the isoflavone group over placebo; trials of longer duration did not necessarily result in a greater improvement in symptoms.

Here are the panel’s key recommendations for women:

  • In postmenopausal women with distressing vasomotor symptoms, initial treatement with isoflavones (aka phytoestrogens) is reasonable.
  • The starting isoflavone dose should be 50 mg/day or higher, and therapy should be given for at least 12 weeks. Dr. Allmen said “if it doesn’t work by then, it’s not going to work.”
  • If a woman responds to isoflavone supplementation, treatment can continue with monitoring for side effects.