NWRC research staff members Laura Hanson, Jeanne Stewart and Kathy Hanson also joined Kenneth Koehler and C. Ted Peterson from statistics as part of the eight-member ISU team that conducted the research.
The researchers ran statistical analyses to determine change in BMD at the lumbar spine, total proximal femur (hip), femoral neck and whole body. They accounted for treatment, age, whole body fat mass and bone removal (using a biochemical marker).
While the 120-mg dose soy isoflavones did reveal a small protective effect on femoral neck bone BMD, researchers found no significant effect of treatment on lumbar spine, total hip, or whole-body BMD.
"This trial used isoflavones extracted from soy protein, compressed into tablet form, consumed over the course of three years, which is very different than either providing soy protein or soy foods," Alekel said. "In our recent study, we did not demonstrate an important biological effect on BMD or bone turnover."
The new study calls into question the value of postmenopausal women consuming soy isoflavone tablets to help lessen bone loss and minimize the effect of osteoporosis.
"The preponderance of studies that have been published -- particularly the longer term, more carefully conducted studies, like our own -- have shown little to no biological effects of soy isoflavones on BMD," she said. "This field of research has attracted 'believers,' making it difficult to convince them otherwise. They may continue to believe what they want to believe, rather than what the evidence shows."
And when it comes to minimizing the consequences of osteoporosis in postmenopausal women, Alekel urges a more holistic approach.
"People in general, would like an easy fix. We would all like soy isoflavones to be that magic pill, but this study has found that they are not," she said.
|Contact: Mike Ferlazzo|
Iowa State University