A new study casts doubt on the value of soy powder as a substitute for estrogen pills. Dutch researchers found that soy did not increase bone density in postmenopausal women, and did not improve their memory or cholesterol levels either.
“The results are, of course, very disappointing,” said study co-author Dr. Sanne Kreijkamp-Kaspers of University Medical Center in Utrecht. “It would have been nice to have soy as an alternative.”
Many women and doctors have been looking for alternatives to estrogen because of recent findings linking estrogen-progestin supplements to heart disease, breast cancer and senility.
Soy contains compounds called isoflavones that mimic the effects of estrogen, and it was thought that soy, like estrogen, might ward off osteoporosis and relieve other symptoms of menopause.
The study, which appears in Wednesday’s Journal of the American Medical Association, involved 202 women ages 60 to 75.
Study may have been timed too late
Half were given supplements of Solae soy protein powder to mix into their food or drink every day for one year; the other half were given milk protein supplements. There were no significant differences between the two groups in mental function, bone density or cholesterol after one year, despite previous studies showing soy works.
The authors noted that most of the women were long past menopause and said it is possible the study was timed too late to enable them to experience any soy-related benefits.
Previous research has suggested that soy might help prevent bone loss immediately after menopause. “But it is much harder to reverse the bone loss when the damage is already done,” Kreijkamp-Kaspers said, adding that the same might be true for mental function.
It is also possible that other soy products would have different results. The study, funded by Dutch research organizations, used only Solae powder, provided by its maker, the Solae Co.
Dr. James Anderson of the University of Kentucky, whose own research found soy protein lowers cholesterol, said older women should not give up on soy. With soy’s rising popularity, many manufacturers use mass-production techniques that can reduce soy protein’s effectiveness, but purer forms are still beneficial, Anderson said.
Wake Forest University researcher Thomas Clarkson said that soy is most beneficial in the presence of estrogen and that it can be effective for postmenopausal women if they also take very low-dose hormone supplements.
Solae’s Greg Paul said the study results “do not reflect the larger body of scientific evidence” showing a variety of benefits from soy protein.
About equal numbers of women quit the study, mainly because of side effects, including digestive problems and complaints about the supplements’ taste. Similar side effects were reported in both groups.
A total of 175 women completed the study.