April 9, 2012 -- Taking soy to relieve hot flashes has received mixed reviews over the years.
Now, researchers who took another look at 19 published studies find that soy supplements may help, at least over time.
Soy has been touted as an alternative treatment to hormone replacement therapy after HRT was linked to an increased risk of breast cancer.
"For many women with symptoms and especially with concerns about hormone replacement therapy, trying soy for six to 12 weeks to see if it relieves their symptoms could be a first line of treatment," says Melissa Melby, PhD, a professor of medical anthropology at the University of Delaware.
The study is published in Menopause: The Journal of The North American Menopause Society.
Two co-authors, not including Melby, have ties to the soy industry. The study had no industry funding.
Although all the studies looked at soy supplements, Melby says that getting soy from food is a better bet.
"What this study shows is that ingesting soy isoflavones will help you," she says. "I personally think foods [containing soy] are better."
Melby looked for published studies of soy for hot flashes in the medical literature through mid-December 2010.
All the studies compared the soy to a placebo. More than 1,200 women were in the studies, which included the U.S. and nine other countries. The studies continued for six weeks up to a year and included different amounts of soy supplements.
The researchers pooled the results of the individual studies to come up with their findings.
Soy supplements with higher amounts of the isoflavone called genistein were more than twice as good at reducing hot flash frequency than those with low amounts, Melby found.
If you prefer to get your soy from food, Melby suggests two servings of soy foods per day. That is roughly equal to two glasses of soy milk, 7 ounces of tofu, or half a cup of edamame.
Soy for Hot Flashes: Second Opinion
The new analysis leaves a lot unanswered, says Silvina Levis, MD, a professor of medicine and director of the osteoporosis center at the University of Miami.