Scientists are exploring the role of natural estrogen-like substances in foods, like soybean isoflavones, in boosting bone health.
Agricultural Research Service (ARS) physiologist Marta D. Van Loan and other researchers at the University of California-Davis said that soy has been studied for a long time due to some of its properties.
Soybean has potential to substitute conventional steroid hormone replacement therapy for postmenopausal women.
The study showed that overall the isoflavones had no significant positive effect on preventing bone loss.
But the 120-mg treatment showed a modest benefit when evaluated in conjunction with lifestyle factors.
The researchers suggest that the body's response to isoflavones extracted from soy proteins may be different from responses to isoflavones in their natural matrix of soy protein or soy foods, or in a soy-protein supplement.
Or, some soy-protein compound other than the extracted isoflavones may have been responsible for the bone-protecting effects seen in some previous studies.
Finally, the isoflavone doses used in the 2010 study may not have been high enough to produce a bone-sparing effect.
The study is published in the American Journal of Clinical Nutrition.