From tempering menopausal symptoms to reducing the risk of several health problems that plague women following it, some women still turn to soy as an alternative to traditional estrogen therapy.
And yet in the latest study, researchers from the Netherlands find that daily soy supplements did not help preserve a women's thinking ability or bone density. The study also showed no evidence that the supplement provided heart protection by improving women's cholesterol levels following menopause.
Why the sudden departure from previous findings that have supported a beneficial effect from soy, the plant-derived estrogen-like compound? Perhaps because the women studied were between ages 60 and 75 when they started taking soy proteins -- when they may have been too old to reap its reported benefits.
Don't Wait too Long
"Timing is certainly a reasonable explanation as to why we didn't find an effect from soy in the women studied," researcher Sanne Kreijkamp-Kaspers, MD, PhD, tells WebMD.
"We know that immediately after menopause, there's a huge decline in bone loss and that's when [bad] cholesterol levels tend to increase," she says. "It could be that if you give soy before a woman reaches menopause, it is effective at preventing this."
If supplementation begins a decade of so after menopause, it may be too late, she explains.
In her study, published in this week's Journal of the American Medical Association, 200 women received either 25 grams of soy protein each day via a powder that could be mixed with food or beverages or a phony powder package. Each daily dose of soy contained 99 milligrams of isoflavones, such as genisten and diadzein, the most common form of phytoestrogen.
None of the women had ever consumed soy supplements prior to the study, according to Kreijkamp-Kaspers, an epidemiologist at University Medical Center in Utrecht. "Soy is not as popular in the Netherlands as it is in the U.S.," she explains.