(Reuters Health) - Plant-derived estrogens, such as those from soy and red clover, might contribute to unwanted weight gain in some postmenopausal women, according to a new review of previous clinical trials.

Known as phytoestrogens, these natural compounds mimic the effects of estrogen in the body. Women entering menopause have a sharp drop in estrogen levels that can lead to hot flashes, night sweats and other unpleasant symptoms.

While hormone replacement therapy remains the most effective treatment for these symptoms, many women choose to take phytoestrogens instead, said lead author Dr. Marija Glisic of University Medical Center Rotterdam in the Netherlands.

“Currently, the European Menopause and Andropause Society suggests non-hormonal treatment as a realistic option in women who do not wish to take hormonal therapy or in whom hormonal therapy is contraindicated,” Glisic said in an email.

However, it remains unclear whether phytoestrogens help or hurt with regard to the weight gain and other body changes that typically accompany menopause, the study team writes in Maturitas.

To investigate, Glisic and her colleagues reviewed 23 randomized controlled trials involving a total of 1,880 postmenopausal women. All the trials compared women assigned to take phytoestrogens or a placebo, who were at least four years past menopause, and who were consuming a regular diet, not seeking to lose weight. Trials took place in Asia, Europe and North and South America.

Overall, Glisic’s team found no associations between taking phytoestrogen supplements and weight gain or loss, or any other changes in measurements of body composition like waist-to-hip ratio. When they looked at certain subgroups of women, however, there were some slight but statistically meaningful differences.

Among women who already had metabolic problems such as diabetes, high blood pressure or high cholesterol, those who took phytoestrogens ended up weighing about 0.8 kilograms, or 1.7 pounds, more than those on placebo. Healthy women on phytoestrogens weighed about 0.3 kilograms less, or 0.6 pounds, compared to those on placebo.

“Also, there is some evidence that supplements containing isoflavone mixture could have minimal beneficial effect while daidzein-enriched isoflavones may lead to increased body weight,” Glisic noted. She and her colleagues recommend that consumers look at the ingredient list of isoflavone formulations and choose those with the least daidzein.

Current research on phytoestrogens and weight is of poor quality, and most trials the researchers analyzed had been published in 2013 or earlier, Glisic added. “We may assume that the formulation and quality of recent supplements may be different as compared to supplements that were used five or more years ago.”

Two of the study’s authors have received research support from Metagenics, Inc., a California-based company that sells nutritional supplements, including phytoestrogen preparations for treating menopausal symptoms.

SOURCE: bit.ly/2vafkj6 Maturitas, online June 22, 2018.